Re: [PATCH] KVM: PPC: fix ONE_REG AltiVec support

[Greg Kurz]

Happy new year !

On Wed, 16 Dec 2015 18:24:03 +0100
Greg Kurz <gk...@linux.vnet.ibm.com> wrote:

> The get and set operations got exchanged by mistake when moving the
> code from book3s.c to powerpc.c.
> 
> Fixes: 3840edc8033ad5b86deee309c1c321ca54257452
> Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> ---
> 

Ping ?

> It's been there for over a year but I guess we want that in 4.4, even
> if doesn't break the host kernel.
> 
>  arch/powerpc/kvm/powerpc.c |   20 ++--
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 6fd2405c7f4a..a3b182dcb823 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -919,21 +919,17 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, 
> struct kvm_one_reg *reg)
>   r = -ENXIO;
>   break;
>   }
> - vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
> + val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
>   break;
>   case KVM_REG_PPC_VSCR:
>   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
>   r = -ENXIO;
>   break;
>   }
> - vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
> + val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
>   break;
>   case KVM_REG_PPC_VRSAVE:
> - if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
> - r = -ENXIO;
> - break;
> - }
> - vcpu->arch.vrsave = set_reg_val(reg->id, val);
> + val = get_reg_val(reg->id, vcpu->arch.vrsave);
>   break;
>  #endif /* CONFIG_ALTIVEC */
>   default:
> @@ -974,17 +970,21 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, 
> struct kvm_one_reg *reg)
>   r = -ENXIO;
>   break;
>   }
> - val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
> + vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
>   break;
>   case KVM_REG_PPC_VSCR:
>   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
>   r = -ENXIO;
>   break;
>   }
> - val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
> + vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
>   break;
>   case KVM_REG_PPC_VRSAVE:
> - val = get_reg_val(reg->id, vcpu->arch.vrsave);
> + if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
> + r = -ENXIO;
> + break;
> + }
> + vcpu->arch.vrsave = set_reg_val(reg->id, val);
>   break;
>  #endif /* CONFIG_ALTIVEC */
>   default:
> 
> --
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> the body of a message to majord...@vger.kernel.org
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> 

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Re: [PATCH] KVM: PPC: fix ONE_REG AltiVec support

[Greg Kurz]

Happy new year !

On Wed, 16 Dec 2015 18:24:03 +0100
Greg Kurz <gk...@linux.vnet.ibm.com> wrote:

> The get and set operations got exchanged by mistake when moving the
> code from book3s.c to powerpc.c.
> 
> Fixes: 3840edc8033ad5b86deee309c1c321ca54257452
> Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> ---
> 

Ping ?

> It's been there for over a year but I guess we want that in 4.4, even
> if doesn't break the host kernel.
> 
>  arch/powerpc/kvm/powerpc.c |   20 ++--
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 6fd2405c7f4a..a3b182dcb823 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -919,21 +919,17 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, 
> struct kvm_one_reg *reg)
>   r = -ENXIO;
>   break;
>   }
> - vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
> + val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
>   break;
>   case KVM_REG_PPC_VSCR:
>   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
>   r = -ENXIO;
>   break;
>   }
> - vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
> + val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
>   break;
>   case KVM_REG_PPC_VRSAVE:
> - if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
> - r = -ENXIO;
> - break;
> - }
> - vcpu->arch.vrsave = set_reg_val(reg->id, val);
> + val = get_reg_val(reg->id, vcpu->arch.vrsave);
>   break;
>  #endif /* CONFIG_ALTIVEC */
>   default:
> @@ -974,17 +970,21 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, 
> struct kvm_one_reg *reg)
>   r = -ENXIO;
>   break;
>   }
> - val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
> + vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
>   break;
>   case KVM_REG_PPC_VSCR:
>   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
>   r = -ENXIO;
>   break;
>   }
> - val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
> + vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
>   break;
>   case KVM_REG_PPC_VRSAVE:
> - val = get_reg_val(reg->id, vcpu->arch.vrsave);
> + if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
> + r = -ENXIO;
> + break;
> + }
> + vcpu->arch.vrsave = set_reg_val(reg->id, val);
>   break;
>  #endif /* CONFIG_ALTIVEC */
>   default:
> 
> --
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> 

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[PATCH] KVM: PPC: fix ONE_REG AltiVec support

[Greg Kurz]

The get and set operations got exchanged by mistake when moving the
code from book3s.c to powerpc.c.

Fixes: 3840edc8033ad5b86deee309c1c321ca54257452
Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
---

It's been there for over a year but I guess we want that in 4.4, even
if doesn't break the host kernel.

 arch/powerpc/kvm/powerpc.c |   20 ++--
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 6fd2405c7f4a..a3b182dcb823 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -919,21 +919,17 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, 
struct kvm_one_reg *reg)
r = -ENXIO;
break;
}
-   vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
+   val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
break;
case KVM_REG_PPC_VSCR:
if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
r = -ENXIO;
break;
}
-   vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
+   val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
break;
case KVM_REG_PPC_VRSAVE:
-   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
-   r = -ENXIO;
-   break;
-   }
-   vcpu->arch.vrsave = set_reg_val(reg->id, val);
+   val = get_reg_val(reg->id, vcpu->arch.vrsave);
break;
 #endif /* CONFIG_ALTIVEC */
default:
@@ -974,17 +970,21 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, 
struct kvm_one_reg *reg)
r = -ENXIO;
break;
}
-   val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
+   vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
break;
case KVM_REG_PPC_VSCR:
if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
r = -ENXIO;
break;
}
-   val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
+   vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
break;
case KVM_REG_PPC_VRSAVE:
-   val = get_reg_val(reg->id, vcpu->arch.vrsave);
+   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
+   r = -ENXIO;
+   break;
+   }
+   vcpu->arch.vrsave = set_reg_val(reg->id, val);
break;
 #endif /* CONFIG_ALTIVEC */
default:

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[PATCH] KVM: PPC: fix ONE_REG AltiVec support

[Greg Kurz]

The get and set operations got exchanged by mistake when moving the
code from book3s.c to powerpc.c.

Fixes: 3840edc8033ad5b86deee309c1c321ca54257452
Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
---

It's been there for over a year but I guess we want that in 4.4, even
if doesn't break the host kernel.

 arch/powerpc/kvm/powerpc.c |   20 ++--
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 6fd2405c7f4a..a3b182dcb823 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -919,21 +919,17 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, 
struct kvm_one_reg *reg)
r = -ENXIO;
break;
}
-   vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
+   val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
break;
case KVM_REG_PPC_VSCR:
if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
r = -ENXIO;
break;
}
-   vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
+   val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
break;
case KVM_REG_PPC_VRSAVE:
-   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
-   r = -ENXIO;
-   break;
-   }
-   vcpu->arch.vrsave = set_reg_val(reg->id, val);
+   val = get_reg_val(reg->id, vcpu->arch.vrsave);
break;
 #endif /* CONFIG_ALTIVEC */
default:
@@ -974,17 +970,21 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, 
struct kvm_one_reg *reg)
r = -ENXIO;
break;
}
-   val.vval = vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0];
+   vcpu->arch.vr.vr[reg->id - KVM_REG_PPC_VR0] = val.vval;
break;
case KVM_REG_PPC_VSCR:
if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
r = -ENXIO;
break;
}
-   val = get_reg_val(reg->id, vcpu->arch.vr.vscr.u[3]);
+   vcpu->arch.vr.vscr.u[3] = set_reg_val(reg->id, val);
break;
case KVM_REG_PPC_VRSAVE:
-   val = get_reg_val(reg->id, vcpu->arch.vrsave);
+   if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
+   r = -ENXIO;
+   break;
+   }
+   vcpu->arch.vrsave = set_reg_val(reg->id, val);
break;
 #endif /* CONFIG_ALTIVEC */
default:

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Re: [PATCH] vhost: move is_le setup to the backend

[Greg Kurz]

On Thu, 12 Nov 2015 15:28:19 +0100
Greg Kurz <gk...@linux.vnet.ibm.com> wrote:

> On Thu, 12 Nov 2015 15:46:30 +0200
> "Michael S. Tsirkin" <m...@redhat.com> wrote:
> 
> > On Fri, Oct 30, 2015 at 12:42:35PM +0100, Greg Kurz wrote:
> > > The vq->is_le field is used to fix endianness when accessing the vring via
> > > the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases:
> > > 
> > > 1) host is big endian and device is modern virtio
> > > 
> > > 2) host has cross-endian support and device is legacy virtio with a 
> > > different
> > >endianness than the host
> > > 
> > > Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the
> > > VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le
> > > is only needed when the backend is active, it was decided to set it at
> > > backend start.
> > > 
> > > This is currently done in vhost_init_used()->vhost_init_is_le() but it
> > > obfuscates the core vhost code. This patch moves the is_le setup to a
> > > dedicated function that is called from the backend code.
> > > 
> > > Note vhost_net is the only backend that can pass vq->private_data == NULL 
> > > to
> > > vhost_init_used(), hence the "if (sock)" branch.
> > > 
> > > No behaviour change.
> > > 
> > > Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> > 
> > I plan to look at this next week, busy with QEMU 2.5 now.
> > 
> 
> I don't have any deadline for this since this is only a cleanup tentative.
> 
> Thanks.
> 

... but ping anyway since it was a month ago :)

Cheers.

--
Greg

> > > ---
> > >  drivers/vhost/net.c   |6 ++
> > >  drivers/vhost/scsi.c  |3 +++
> > >  drivers/vhost/test.c  |2 ++
> > >  drivers/vhost/vhost.c |   12 +++-
> > >  drivers/vhost/vhost.h |1 +
> > >  5 files changed, 19 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > > index 9eda69e40678..d6319cb2664c 100644
> > > --- a/drivers/vhost/net.c
> > > +++ b/drivers/vhost/net.c
> > > @@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net 
> > > *n, unsigned index, int fd)
> > >  
> > >   vhost_net_disable_vq(n, vq);
> > >   vq->private_data = sock;
> > > +
> > > + if (sock)
> > > + vhost_set_is_le(vq);
> > > + else
> > > + vq->is_le = virtio_legacy_is_little_endian();
> > > +
> > >   r = vhost_init_used(vq);
> > >   if (r)
> > >   goto err_used;
> > > diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> > > index e25a23692822..e2644a301fa5 100644
> > > --- a/drivers/vhost/scsi.c
> > > +++ b/drivers/vhost/scsi.c
> > > @@ -1276,6 +1276,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
> > >   vq = >vqs[i].vq;
> > >   mutex_lock(>mutex);
> > >   vq->private_data = vs_tpg;
> > > +
> > > + vhost_set_is_le(vq);
> > > +
> > >   vhost_init_used(vq);
> > >   mutex_unlock(>mutex);
> > >   }
> > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> > > index f2882ac98726..b1c7df502211 100644
> > > --- a/drivers/vhost/test.c
> > > +++ b/drivers/vhost/test.c
> > > @@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int 
> > > test)
> > >   oldpriv = vq->private_data;
> > >   vq->private_data = priv;
> > >  
> > > + vhost_set_is_le(vq);
> > > +
> > >   r = vhost_init_used(>vqs[index]);
> > >  
> > >   mutex_unlock(>mutex);
> > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > > index eec2f11809ff..6be863dcbd13 100644
> > > --- a/drivers/vhost/vhost.c
> > > +++ b/drivers/vhost/vhost.c
> > > @@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue 
> > > *vq)
> > >  }
> > >  #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
> > >  
> > > +void vhost_set_is_le(struct vhost_virtqueue *vq)
> > > +{
> > > + vhost_init_is_le(vq);
> > > +}
> > > +EXPORT_SYMBOL_GPL(vhost_

Re: [PATCH] vhost: move is_le setup to the backend

[Greg Kurz]

On Fri, 30 Oct 2015 12:42:35 +0100
Greg Kurz <gk...@linux.vnet.ibm.com> wrote:

> The vq->is_le field is used to fix endianness when accessing the vring via
> the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases:
> 
> 1) host is big endian and device is modern virtio
> 
> 2) host has cross-endian support and device is legacy virtio with a different
>endianness than the host
> 
> Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the
> VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le
> is only needed when the backend is active, it was decided to set it at
> backend start.
> 
> This is currently done in vhost_init_used()->vhost_init_is_le() but it
> obfuscates the core vhost code. This patch moves the is_le setup to a
> dedicated function that is called from the backend code.
> 
> Note vhost_net is the only backend that can pass vq->private_data == NULL to
> vhost_init_used(), hence the "if (sock)" branch.
> 
> No behaviour change.
> 
> Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> ---

Ping ?

>  drivers/vhost/net.c   |6 ++
>  drivers/vhost/scsi.c  |3 +++
>  drivers/vhost/test.c  |2 ++
>  drivers/vhost/vhost.c |   12 +++-
>  drivers/vhost/vhost.h |1 +
>  5 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 9eda69e40678..d6319cb2664c 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net *n, 
> unsigned index, int fd)
> 
>   vhost_net_disable_vq(n, vq);
>   vq->private_data = sock;
> +
> + if (sock)
> + vhost_set_is_le(vq);
> + else
> + vq->is_le = virtio_legacy_is_little_endian();
> +
>   r = vhost_init_used(vq);
>   if (r)
>   goto err_used;
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index e25a23692822..e2644a301fa5 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -1276,6 +1276,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
>   vq = >vqs[i].vq;
>   mutex_lock(>mutex);
>   vq->private_data = vs_tpg;
> +
> + vhost_set_is_le(vq);
> +
>   vhost_init_used(vq);
>   mutex_unlock(>mutex);
>   }
> diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> index f2882ac98726..b1c7df502211 100644
> --- a/drivers/vhost/test.c
> +++ b/drivers/vhost/test.c
> @@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int test)
>   oldpriv = vq->private_data;
>   vq->private_data = priv;
> 
> + vhost_set_is_le(vq);
> +
>   r = vhost_init_used(>vqs[index]);
> 
>   mutex_unlock(>mutex);
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index eec2f11809ff..6be863dcbd13 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue *vq)
>  }
>  #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
> 
> +void vhost_set_is_le(struct vhost_virtqueue *vq)
> +{
> + vhost_init_is_le(vq);
> +}
> +EXPORT_SYMBOL_GPL(vhost_set_is_le);
> +
>  static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
>   poll_table *pt)
>  {
> @@ -1156,12 +1162,8 @@ int vhost_init_used(struct vhost_virtqueue *vq)
>  {
>   __virtio16 last_used_idx;
>   int r;
> - if (!vq->private_data) {
> - vq->is_le = virtio_legacy_is_little_endian();
> + if (!vq->private_data)
>   return 0;
> - }
> -
> - vhost_init_is_le(vq);
> 
>   r = vhost_update_used_flags(vq);
>   if (r)
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 4772862b71a7..8a62041959fe 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -162,6 +162,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct 
> vhost_virtqueue *);
> 
>  int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
>   unsigned int log_num, u64 len);
> +void vhost_set_is_le(struct vhost_virtqueue *vq);
> 
>  #define vq_err(vq, fmt, ...) do {  \
>   pr_debug(pr_fmt(fmt), ##__VA_ARGS__);   \
> 
> --
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> the body of a message to majord...@vger.kernel.org
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Re: [PATCH] vhost: move is_le setup to the backend

[Greg Kurz]

On Thu, 12 Nov 2015 15:46:30 +0200
"Michael S. Tsirkin" <m...@redhat.com> wrote:

> On Fri, Oct 30, 2015 at 12:42:35PM +0100, Greg Kurz wrote:
> > The vq->is_le field is used to fix endianness when accessing the vring via
> > the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases:
> > 
> > 1) host is big endian and device is modern virtio
> > 
> > 2) host has cross-endian support and device is legacy virtio with a 
> > different
> >endianness than the host
> > 
> > Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the
> > VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le
> > is only needed when the backend is active, it was decided to set it at
> > backend start.
> > 
> > This is currently done in vhost_init_used()->vhost_init_is_le() but it
> > obfuscates the core vhost code. This patch moves the is_le setup to a
> > dedicated function that is called from the backend code.
> > 
> > Note vhost_net is the only backend that can pass vq->private_data == NULL to
> > vhost_init_used(), hence the "if (sock)" branch.
> > 
> > No behaviour change.
> > 
> > Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> 
> I plan to look at this next week, busy with QEMU 2.5 now.
> 

I don't have any deadline for this since this is only a cleanup tentative.

Thanks.

> > ---
> >  drivers/vhost/net.c   |6 ++
> >  drivers/vhost/scsi.c  |3 +++
> >  drivers/vhost/test.c  |2 ++
> >  drivers/vhost/vhost.c |   12 +++-
> >  drivers/vhost/vhost.h |1 +
> >  5 files changed, 19 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index 9eda69e40678..d6319cb2664c 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net *n, 
> > unsigned index, int fd)
> >  
> > vhost_net_disable_vq(n, vq);
> > vq->private_data = sock;
> > +
> > +   if (sock)
> > +   vhost_set_is_le(vq);
> > +   else
> > +   vq->is_le = virtio_legacy_is_little_endian();
> > +
> > r = vhost_init_used(vq);
> > if (r)
> > goto err_used;
> > diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> > index e25a23692822..e2644a301fa5 100644
> > --- a/drivers/vhost/scsi.c
> > +++ b/drivers/vhost/scsi.c
> > @@ -1276,6 +1276,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
> > vq = >vqs[i].vq;
> > mutex_lock(>mutex);
> > vq->private_data = vs_tpg;
> > +
> > +   vhost_set_is_le(vq);
> > +
> > vhost_init_used(vq);
> > mutex_unlock(>mutex);
> > }
> > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> > index f2882ac98726..b1c7df502211 100644
> > --- a/drivers/vhost/test.c
> > +++ b/drivers/vhost/test.c
> > @@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int 
> > test)
> > oldpriv = vq->private_data;
> > vq->private_data = priv;
> >  
> > +   vhost_set_is_le(vq);
> > +
> > r = vhost_init_used(>vqs[index]);
> >  
> > mutex_unlock(>mutex);
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index eec2f11809ff..6be863dcbd13 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue 
> > *vq)
> >  }
> >  #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
> >  
> > +void vhost_set_is_le(struct vhost_virtqueue *vq)
> > +{
> > +   vhost_init_is_le(vq);
> > +}
> > +EXPORT_SYMBOL_GPL(vhost_set_is_le);
> > +
> >  static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
> > poll_table *pt)
> >  {
> > @@ -1156,12 +1162,8 @@ int vhost_init_used(struct vhost_virtqueue *vq)
> >  {
> > __virtio16 last_used_idx;
> > int r;
> > -   if (!vq->private_data) {
> > -   vq->is_le = virtio_legacy_is_little_endian();
> > +   if (!vq->private_data)
> > return 0;
> > -   }
> > -
> > -   vhost_init_is_le(vq);
> >  
> > r = vhost_update_used_flags(vq);
> >   

[PATCH] vhost: move is_le setup to the backend

[Greg Kurz]

The vq->is_le field is used to fix endianness when accessing the vring via
the cpu_to_vhost16() and vhost16_to_cpu() helpers in the following cases:

1) host is big endian and device is modern virtio

2) host has cross-endian support and device is legacy virtio with a different
   endianness than the host

Both cases rely on the VHOST_SET_FEATURES ioctl, but 2) also needs the
VHOST_SET_VRING_ENDIAN ioctl to be called by userspace. Since vq->is_le
is only needed when the backend is active, it was decided to set it at
backend start.

This is currently done in vhost_init_used()->vhost_init_is_le() but it
obfuscates the core vhost code. This patch moves the is_le setup to a
dedicated function that is called from the backend code.

Note vhost_net is the only backend that can pass vq->private_data == NULL to
vhost_init_used(), hence the "if (sock)" branch.

No behaviour change.

Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
---
 drivers/vhost/net.c   |6 ++
 drivers/vhost/scsi.c  |3 +++
 drivers/vhost/test.c  |2 ++
 drivers/vhost/vhost.c |   12 +++-
 drivers/vhost/vhost.h |1 +
 5 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9eda69e40678..d6319cb2664c 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -917,6 +917,12 @@ static long vhost_net_set_backend(struct vhost_net *n, 
unsigned index, int fd)
 
vhost_net_disable_vq(n, vq);
vq->private_data = sock;
+
+   if (sock)
+   vhost_set_is_le(vq);
+   else
+   vq->is_le = virtio_legacy_is_little_endian();
+
r = vhost_init_used(vq);
if (r)
goto err_used;
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index e25a23692822..e2644a301fa5 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1276,6 +1276,9 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
vq = >vqs[i].vq;
mutex_lock(>mutex);
vq->private_data = vs_tpg;
+
+   vhost_set_is_le(vq);
+
vhost_init_used(vq);
mutex_unlock(>mutex);
}
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index f2882ac98726..b1c7df502211 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -196,6 +196,8 @@ static long vhost_test_run(struct vhost_test *n, int test)
oldpriv = vq->private_data;
vq->private_data = priv;
 
+   vhost_set_is_le(vq);
+
r = vhost_init_used(>vqs[index]);
 
mutex_unlock(>mutex);
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index eec2f11809ff..6be863dcbd13 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -113,6 +113,12 @@ static void vhost_init_is_le(struct vhost_virtqueue *vq)
 }
 #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
 
+void vhost_set_is_le(struct vhost_virtqueue *vq)
+{
+   vhost_init_is_le(vq);
+}
+EXPORT_SYMBOL_GPL(vhost_set_is_le);
+
 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
 {
@@ -1156,12 +1162,8 @@ int vhost_init_used(struct vhost_virtqueue *vq)
 {
__virtio16 last_used_idx;
int r;
-   if (!vq->private_data) {
-   vq->is_le = virtio_legacy_is_little_endian();
+   if (!vq->private_data)
return 0;
-   }
-
-   vhost_init_is_le(vq);
 
r = vhost_update_used_flags(vq);
if (r)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 4772862b71a7..8a62041959fe 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -162,6 +162,7 @@ bool vhost_enable_notify(struct vhost_dev *, struct 
vhost_virtqueue *);
 
 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
unsigned int log_num, u64 len);
+void vhost_set_is_le(struct vhost_virtqueue *vq);
 
 #define vq_err(vq, fmt, ...) do {  \
pr_debug(pr_fmt(fmt), ##__VA_ARGS__);   \

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Re: [PATCH] vhost: fix performance on LE hosts

[Greg Kurz]

On Tue, 27 Oct 2015 11:37:39 +0200
"Michael S. Tsirkin" <m...@redhat.com> wrote:
> commit 2751c9882b947292fcfb084c4f604e01724af804 ("vhost: cross-endian
> support for legacy devices") introduced a minor regression: even with
> cross-endian disabled, and even on LE host, vhost_is_little_endian is
> checking is_le flag so there's always a branch.
> 
> To fix, simply check virtio_legacy_is_little_endian first.
> 
> Cc: Greg Kurz <gk...@linux.vnet.ibm.com>
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>

Oops my bad for this oversight...

Reviewed-by: Greg Kurz <gk...@linux.vnet.ibm.com>

> ---
>  drivers/vhost/vhost.h | 7 +++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 4772862..d3f7674 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -183,10 +183,17 @@ static inline bool vhost_has_feature(struct 
> vhost_virtqueue *vq, int bit)
>   return vq->acked_features & (1ULL << bit);
>  }
> 
> +#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
>  static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
>  {
>   return vq->is_le;
>  }
> +#else
> +static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
> +{
> + return virtio_legacy_is_little_endian() || vq->is_le;
> +}
> +#endif
> 
>  /* Memory accessors */
>  static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)

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Re: [PATCH v2] Fix AF_PACKET ABI breakage in 4.2

[Greg Kurz]

On Thu, 24 Sep 2015 12:50:59 +0300
"Michael S. Tsirkin" <m...@redhat.com> wrote:

> On Thu, Sep 24, 2015 at 09:25:45AM +0200, Greg Kurz wrote:
> > On Wed, 23 Sep 2015 19:45:08 +0100
> > David Woodhouse <dw...@infradead.org> wrote:
> > 
> > > Commit 7d82410950aa ("virtio: add explicit big-endian support to memory
> > > accessors") accidentally changed the virtio_net header used by
> > > AF_PACKET with PACKET_VNET_HDR from host-endian to big-endian.
> > > 
> > 
> > Hi David,
> > 
> > Oops my bad... I obviously overlooked this one when adding cross-endian
> > support.
> > 
> > > Since virtio_legacy_is_little_endian() is a very long identifier,
> > > define a VIO_LE macro and use that throughout the code instead of the
> > 
> > VIO usually refers to virtual IO adapters for the PowerPC pSeries platform.
> > 
> > > hard-coded 'false' for little-endian.
> > > 
> > 
> > What about introducing dedicated accessors as it is done in many other
> > locations where we do virtio byteswap ? Something like:
> > 
> > static inline bool packet_is_little_endian(void)
> > {
> > return virtio_legacy_is_little_endian();
> > }
> > 
> > static inline u16 packet16_to_cpu(__virtio16 val)
> > {
> > return __virtio16_to_cpu(packet_is_little_endian(), val);
> > }
> > 
> > static inline __virtio16 cpu_to_packet16(u16 val)
> > {
> > return __cpu_to_virtio16(packet_is_little_endian(), val);
> > }
> > 
> > It results in prettier code IMHO. Have a look at drivers/net/tun.c or
> > drivers/vhost/vhost.c.
> > 
> > > This restores the ABI to match 4.1 and earlier kernels, and makes my
> > > test program work again.
> > > 
> > 
> > BTW, there is still work to do if we want to support cross-endian legacy or
> > virtio 1 on a big endian arch...
> > 
> > Cheers.
> > 
> > --
> > Greg
> 
> It seems the API that we have is a confusing one.
> 
> virtio endian-ness is either native or little, depending on a flag, so
> __virtio16_to_cpu seems to mean "either native to cpu or little to cpu
> depending on flag".
> 
> It used to be like that, but not anymore.
> 
> This leads to all kind of bugs.
> 
> For example, I have only now realized vhost_is_little_endian isn't a
> constant on LE hosts if cross-endian support is not compiled.
> 
> I think we need to fix it, but also think about a better API.
> 

Your original API is good and works well for all the callers that
don't care for cross-endian support.

I guess we'd rather move the cross-endian burden to the few callers who
need it, i.e. tun, macvtap and vhost when cross-endian is compiled.

More or less like this:

/* Original API : either little-endian or native */
static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
{
if (little_endian)
return le16_to_cpu((__force __le16)val);
else
return (__force u16)val;
}

#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY

static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
{
/* little-endian because of virtio 1 */
if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
return __virtio16_to_cpu(true, val);

#ifdef __LITTLE_ENDIAN
/* native little-endian */
return (__force u16)val;
#else
/* native big-endian */
return be16_to_cpu((__force __be16)val);
#endif
}

#else

static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
{
#ifdef __LITTLE_ENDIAN
/* fast path for little-endian host */
return __virtio16_to_cpu(true, val);
#else
/* slow path for big-endian host */
return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
#endif
}

#endif

Does it make sense ?

> 
> > > Signed-off-by: David Woodhouse <david.woodho...@intel.com>
> > > ---
> > > On Wed, 2015-09-23 at 11:09 -0700, David Miller wrote:
> > > > > +#define VIO_LE virtio_legacy_is_little_endian()
> > > > 
> > > > When you define a shorthand macro, the defines to a function call,
> > > > make the macro have parenthesis too.
> > > 
> > > In which case I suppose it also wants to be lower-case. Although
> > > "function call" is a bit strong since it's effectively just a constant.
> > > I'm still wondering if it'd be nicer just to use (__force u16) instead.
> > > 
> > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> > > index 7b8e39a..aa4b15c 100644
> > > --- a

Re: [PATCH v2] Fix AF_PACKET ABI breakage in 4.2

[Greg Kurz]

On Wed, 23 Sep 2015 19:45:08 +0100
David Woodhouse  wrote:

> Commit 7d82410950aa ("virtio: add explicit big-endian support to memory
> accessors") accidentally changed the virtio_net header used by
> AF_PACKET with PACKET_VNET_HDR from host-endian to big-endian.
> 

Hi David,

Oops my bad... I obviously overlooked this one when adding cross-endian
support.

> Since virtio_legacy_is_little_endian() is a very long identifier,
> define a VIO_LE macro and use that throughout the code instead of the

VIO usually refers to virtual IO adapters for the PowerPC pSeries platform.

> hard-coded 'false' for little-endian.
> 

What about introducing dedicated accessors as it is done in many other
locations where we do virtio byteswap ? Something like:

static inline bool packet_is_little_endian(void)
{
return virtio_legacy_is_little_endian();
}

static inline u16 packet16_to_cpu(__virtio16 val)
{
return __virtio16_to_cpu(packet_is_little_endian(), val);
}

static inline __virtio16 cpu_to_packet16(u16 val)
{
return __cpu_to_virtio16(packet_is_little_endian(), val);
}

It results in prettier code IMHO. Have a look at drivers/net/tun.c or
drivers/vhost/vhost.c.

> This restores the ABI to match 4.1 and earlier kernels, and makes my
> test program work again.
> 

BTW, there is still work to do if we want to support cross-endian legacy or
virtio 1 on a big endian arch...

Cheers.

--
Greg

> Signed-off-by: David Woodhouse 
> ---
> On Wed, 2015-09-23 at 11:09 -0700, David Miller wrote:
> > > +#define VIO_LE virtio_legacy_is_little_endian()
> > 
> > When you define a shorthand macro, the defines to a function call,
> > make the macro have parenthesis too.
> 
> In which case I suppose it also wants to be lower-case. Although
> "function call" is a bit strong since it's effectively just a constant.
> I'm still wondering if it'd be nicer just to use (__force u16) instead.
> 
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 7b8e39a..aa4b15c 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -230,6 +230,8 @@ struct packet_skb_cb {
>   } sa;
>  };
>  
> +#define vio_le() virtio_legacy_is_little_endian()
> +
>  #define PACKET_SKB_CB(__skb) ((struct packet_skb_cb *)((__skb)->cb))
>  
>  #define GET_PBDQC_FROM_RB(x) ((struct tpacket_kbdq_core *)(&(x)->prb_bdqc))
> @@ -2680,15 +2682,15 @@ static int packet_snd(struct socket *sock, struct 
> msghdr *msg, size_t len)
>   goto out_unlock;
>  
>   if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
> - (__virtio16_to_cpu(false, vnet_hdr.csum_start) +
> -  __virtio16_to_cpu(false, vnet_hdr.csum_offset) + 2 >
> -   __virtio16_to_cpu(false, vnet_hdr.hdr_len)))
> - vnet_hdr.hdr_len = __cpu_to_virtio16(false,
> -  __virtio16_to_cpu(false, vnet_hdr.csum_start) +
> - __virtio16_to_cpu(false, vnet_hdr.csum_offset) 
> + 2);
> + (__virtio16_to_cpu(vio_le(), vnet_hdr.csum_start) +
> +  __virtio16_to_cpu(vio_le(), vnet_hdr.csum_offset) + 2 >
> +   __virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len)))
> + vnet_hdr.hdr_len = __cpu_to_virtio16(vio_le(),
> +  __virtio16_to_cpu(vio_le(), 
> vnet_hdr.csum_start) +
> + __virtio16_to_cpu(vio_le(), 
> vnet_hdr.csum_offset) + 2);
>  
>   err = -EINVAL;
> - if (__virtio16_to_cpu(false, vnet_hdr.hdr_len) > len)
> + if (__virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len) > len)
>   goto out_unlock;
>  
>   if (vnet_hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
> @@ -2731,7 +2733,7 @@ static int packet_snd(struct socket *sock, struct 
> msghdr *msg, size_t len)
>   hlen = LL_RESERVED_SPACE(dev);
>   tlen = dev->needed_tailroom;
>   skb = packet_alloc_skb(sk, hlen + tlen, hlen, len,
> -__virtio16_to_cpu(false, vnet_hdr.hdr_len),
> +__virtio16_to_cpu(vio_le(), vnet_hdr.hdr_len),
>  msg->msg_flags & MSG_DONTWAIT, );
>   if (skb == NULL)
>   goto out_unlock;
> @@ -2778,8 +2780,8 @@ static int packet_snd(struct socket *sock, struct 
> msghdr *msg, size_t len)
>  
>   if (po->has_vnet_hdr) {
>   if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
> - u16 s = __virtio16_to_cpu(false, vnet_hdr.csum_start);
> - u16 o = __virtio16_to_cpu(false, vnet_hdr.csum_offset);
> + u16 s = __virtio16_to_cpu(vio_le(), 
> vnet_hdr.csum_start);
> + u16 o = __virtio16_to_cpu(vio_le(), 
> vnet_hdr.csum_offset);
>   if (!skb_partial_csum_set(skb, s, o)) {
>   err = -EINVAL;
> 

Re: [PATCH v4] ppc/spapr: Implement H_RANDOM hypercall in QEMU

[Greg Kurz]

On Mon, 21 Sep 2015 12:10:00 +1000
David Gibson <da...@gibson.dropbear.id.au> wrote:

> On Fri, Sep 18, 2015 at 11:05:52AM +0200, Greg Kurz wrote:
> > On Thu, 17 Sep 2015 10:49:41 +0200
> > Thomas Huth <th...@redhat.com> wrote:
> > 
> > > The PAPR interface defines a hypercall to pass high-quality
> > > hardware generated random numbers to guests. Recent kernels can
> > > already provide this hypercall to the guest if the right hardware
> > > random number generator is available. But in case the user wants
> > > to use another source like EGD, or QEMU is running with an older
> > > kernel, we should also have this call in QEMU, so that guests that
> > > do not support virtio-rng yet can get good random numbers, too.
> > > 
> > > This patch now adds a new pseudo-device to QEMU that either
> > > directly provides this hypercall to the guest or is able to
> > > enable the in-kernel hypercall if available. The in-kernel
> > > hypercall can be enabled with the use-kvm property, e.g.:
> > > 
> > >  qemu-system-ppc64 -device spapr-rng,use-kvm=true
> > > 
> > > For handling the hypercall in QEMU instead, a "RngBackend" is
> > > required since the hypercall should provide "good" random data
> > > instead of pseudo-random (like from a "simple" library function
> > > like rand() or g_random_int()). Since there are multiple RngBackends
> > > available, the user must select an appropriate back-end via the
> > > "rng" property of the device, e.g.:
> > > 
> > >  qemu-system-ppc64 -object rng-random,filename=/dev/hwrng,id=gid0 \
> > >-device spapr-rng,rng=gid0 ...
> > > 
> > > See http://wiki.qemu-project.org/Features-Done/VirtIORNG for
> > > other example of specifying RngBackends.
> > > 
> > > Signed-off-by: Thomas Huth <th...@redhat.com>
> > > ---
> > 
> > It is a good thing that the user can choose between in-kernel and backend,
> > and this patch does the work.
> > 
> > This being said, I am not sure about the use case where a user has a hwrng
> > capable platform and wants to run guests without any hwrng support at all is
> > an appropriate default behavior... I guess we will find more users that want
> > in-kernel being the default if it is available.
> > 
> > The patch below modifies yours to do just this: the pseudo-device is only
> > created if hwrng is present and not already created.
> 
> I have mixed feelings about this.  On the one hand, I agree that it
> would be nice to allow H_RANDOM support by default.  On the other hand
> the patch below leaves no way to turn it off for testing purposes.  It

This could be handled with a new spapr property, say 'use-hwrng', defaulting
to true.

> also adds another place where the guest hardware depends on the host
> configuration, which adds to the already substantial mess of ensuring
> that source and destination hardware configuration matches for
> migration.
> 

Yeah, describing the guest hw is really essential for migration... this
is best addressed at the libvirt level with a full XML description of
the machine... but FWIW if we are talking about running pseries on a
POWER8 or newer host, I am not aware about "hwrng-less" boards... but
I am probably missing something :)

Back to Thomas' patch, it does the job and brings H_RANDOM, which is
currently missing.

Acked-by: Greg Kurz <gk...@linux.vnet.ibm.com>

I could test both use-kvm and backend flavors (including migration).

Tested-by: Greg Kurz <gk...@linux.vnet.ibm.com>

Thanks.

--
Greg


pgpUFFPbPHOji.pgp
Description: OpenPGP digital signature

Re: [PATCH v4] ppc/spapr: Implement H_RANDOM hypercall in QEMU

[Greg Kurz]

On Thu, 17 Sep 2015 10:49:41 +0200
Thomas Huth  wrote:

> The PAPR interface defines a hypercall to pass high-quality
> hardware generated random numbers to guests. Recent kernels can
> already provide this hypercall to the guest if the right hardware
> random number generator is available. But in case the user wants
> to use another source like EGD, or QEMU is running with an older
> kernel, we should also have this call in QEMU, so that guests that
> do not support virtio-rng yet can get good random numbers, too.
> 
> This patch now adds a new pseudo-device to QEMU that either
> directly provides this hypercall to the guest or is able to
> enable the in-kernel hypercall if available. The in-kernel
> hypercall can be enabled with the use-kvm property, e.g.:
> 
>  qemu-system-ppc64 -device spapr-rng,use-kvm=true
> 
> For handling the hypercall in QEMU instead, a "RngBackend" is
> required since the hypercall should provide "good" random data
> instead of pseudo-random (like from a "simple" library function
> like rand() or g_random_int()). Since there are multiple RngBackends
> available, the user must select an appropriate back-end via the
> "rng" property of the device, e.g.:
> 
>  qemu-system-ppc64 -object rng-random,filename=/dev/hwrng,id=gid0 \
>-device spapr-rng,rng=gid0 ...
> 
> See http://wiki.qemu-project.org/Features-Done/VirtIORNG for
> other example of specifying RngBackends.
> 
> Signed-off-by: Thomas Huth 
> ---

It is a good thing that the user can choose between in-kernel and backend,
and this patch does the work.

This being said, I am not sure about the use case where a user has a hwrng
capable platform and wants to run guests without any hwrng support at all is
an appropriate default behavior... I guess we will find more users that want
in-kernel being the default if it is available.

The patch below modifies yours to do just this: the pseudo-device is only
created if hwrng is present and not already created.

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 240fab72e7af..4b92efed2ef3 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -939,6 +939,14 @@ static int spapr_check_htab_fd(sPAPRMachineState *spapr)
 return rc;
 }
 
+static void spapr_rng_create(void)
+{
+Object *rng = object_new(TYPE_SPAPR_RNG);
+
+object_property_set_bool(rng, true, "use-kvm", _abort);
+object_property_set_bool(rng, true, "realized", _abort);
+}
+
 static void ppc_spapr_reset(void)
 {
 sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
@@ -962,6 +970,14 @@ static void ppc_spapr_reset(void)
 spapr->rtas_addr = rtas_limit - RTAS_MAX_SIZE;
 spapr->fdt_addr = spapr->rtas_addr - FDT_MAX_SIZE;
 
+/* Create a rng device if the user did not provide it already and
+ * KVM has hwrng support.
+ */
+if (kvmppc_hwrng_present() &&
+!object_resolve_path_type("", TYPE_SPAPR_RNG, NULL)) {
+spapr_rng_create();
+}
+
 /* Load the fdt */
 spapr_finalize_fdt(spapr, spapr->fdt_addr, spapr->rtas_addr,
spapr->rtas_size);
diff --git a/hw/ppc/spapr_rng.c b/hw/ppc/spapr_rng.c
index ed43d5e04221..ee5af302bd4d 100644
--- a/hw/ppc/spapr_rng.c
+++ b/hw/ppc/spapr_rng.c
@@ -114,7 +114,7 @@ static void spapr_rng_realize(DeviceState *dev, Error 
**errp)
 sPAPRRngState *rngstate = SPAPR_RNG(dev);
 
 if (rngstate->use_kvm) {
-if (kvmppc_enable_hwrng() == 0) {
+if (kvmppc_hwrng_present() && kvmppc_enable_hwrng() == 0) {
 return;
 }
 /*
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 42f66fea23e9..008f8a26ab17 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -2485,11 +2485,12 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
 return data & 0x;
 }
 
-int kvmppc_enable_hwrng(void)
+bool kvmppc_hwrng_present(void)
 {
-if (!kvm_enabled() || !kvm_check_extension(kvm_state, KVM_CAP_PPC_HWRNG)) {
-return -1;
-}
+return kvm_enabled() && kvm_check_extension(kvm_state, KVM_CAP_PPC_HWRNG);
+}
 
+int kvmppc_enable_hwrng(void)
+{
 return kvmppc_enable_hcall(kvm_state, H_RANDOM);
 }
diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
index 68836b401105..4b78bfe5224a 100644
--- a/target-ppc/kvm_ppc.h
+++ b/target-ppc/kvm_ppc.h
@@ -55,6 +55,7 @@ void kvmppc_hash64_free_pteg(uint64_t token);
 void kvmppc_hash64_write_pte(CPUPPCState *env, target_ulong pte_index,
  target_ulong pte0, target_ulong pte1);
 bool kvmppc_has_cap_fixup_hcalls(void);
+bool kvmppc_hwrng_present(void);
 int kvmppc_enable_hwrng(void);
 
 #else
@@ -249,6 +250,11 @@ static inline bool kvmppc_has_cap_fixup_hcalls(void)
 abort();
 }
 
+static inline bool kvmppc_hwrng_present(void)
+{
+return false;
+}
+
 static inline int kvmppc_enable_hwrng(void)
 {
 return -1;

>  hw/ppc/Makefile.objs   |   2 +-
>  hw/ppc/spapr.c |   8 +++
>  hw/ppc/spapr_rng.c | 186 
> 

[PATCH] KVM: PPC: fix typo in top comment about locking

[Greg Kurz]

Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
---
 arch/powerpc/kvm/book3s_xics.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c
index c6ca7db64673..905e94a1370f 100644
--- a/arch/powerpc/kvm/book3s_xics.c
+++ b/arch/powerpc/kvm/book3s_xics.c
@@ -41,7 +41,7 @@
  * ===
  *
  * Each ICS has a spin lock protecting the information about the IRQ
- * sources and avoiding simultaneous deliveries if the same interrupt.
+ * sources and avoiding simultaneous deliveries of the same interrupt.
  *
  * ICP operations are done via a single compare & swap transaction
  * (most ICP state fits in the union kvmppc_icp_state)

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[PATCH] KVM: PPC: fix typo in top comment about locking

[Greg Kurz]

Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
---
 arch/powerpc/kvm/book3s_xics.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c
index c6ca7db64673..905e94a1370f 100644
--- a/arch/powerpc/kvm/book3s_xics.c
+++ b/arch/powerpc/kvm/book3s_xics.c
@@ -41,7 +41,7 @@
  * ===
  *
  * Each ICS has a spin lock protecting the information about the IRQ
- * sources and avoiding simultaneous deliveries if the same interrupt.
+ * sources and avoiding simultaneous deliveries of the same interrupt.
  *
  * ICP operations are done via a single compare & swap transaction
  * (most ICP state fits in the union kvmppc_icp_state)

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Re: [PATCH] KVM: Add Kconfig option to signal cross-endian guests

[Greg Kurz]

On Thu,  9 Jul 2015 09:49:05 +0200
Thomas Huth th...@redhat.com wrote:

 The option for supporting cross-endianness legacy guests in
 the vhost and tun code should only be available on systems
 that support cross-endian guests.
 
 Signed-off-by: Thomas Huth th...@redhat.com

Acked-by: Greg Kurz gk...@linux.vnet.ibm.com

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Re: [PATCH] KVM: Add Kconfig option to signal cross-endian guests

[Greg Kurz]

On Thu,  9 Jul 2015 09:49:05 +0200
Thomas Huth th...@redhat.com wrote:

 The option for supporting cross-endianness legacy guests in
 the vhost and tun code should only be available on systems
 that support cross-endian guests.
 
 Signed-off-by: Thomas Huth th...@redhat.com

Acked-by: Greg Kurz gk...@linux.vnet.ibm.com

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Re: [PULL] virtio/vhost: cross endian support

[Greg Kurz]

On Thu, 2 Jul 2015 08:01:28 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Wed, Jul 01, 2015 at 12:02:50PM -0700, Linus Torvalds wrote:
  On Wed, Jul 1, 2015 at 2:31 AM, Michael S. Tsirkin m...@redhat.com wrote:
   virtio/vhost: cross endian support
  
  Ugh. Does this really have to be dynamic?
  
  Can't virtio do the sane thing, and just use a _fixed_ endianness?
  
  Doing a unconditional byte swap is faster and simpler than the crazy
  conditionals. That's true regardless of endianness, but gets to be
  even more so if the fixed endianness is little-endian, since BE is
  not-so-slowly fading from the world.
  
 Linus
 
 Yea, well - support for legacy BE guests on the new LE hosts is
 exactly the motivation for this.
 
 I dislike it too, but there are two redeeming properties that
 made me merge this:
 
 1.  It's a trivial amount of code: since we wrap host/guest accesses
 anyway, almost all of it is well hidden from drivers.
 
 2.  Sane platforms would never set flags like VHOST_CROSS_ENDIAN_LEGACY -
 and when it's clear, there's zero overhead (as some point it was
 tested by compiling with and without the patches, got the same
 stripped binary).
 
 Maybe we could create a Kconfig symbol to enforce point (2): prevent
 people from enabling it e.g. on x86. I will look into this - but it can
 be done by a patch on top, so I think this can be merged as is.
 

This cross-endian *oddity* is targeting PowerPC book3s_64 processors... I
am not aware of any other users. Maybe create a symbol that would
be only selected by PPC_BOOK3S_64 ?


 Or do you know of someone using kernel with all config options enabled
 undiscriminately?
 
 Thanks,
 

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Re: [PATCH v6 0/8] vhost: support for cross endian guests

[Greg Kurz]

On Tue, 12 May 2015 12:52:55 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Tue, May 12, 2015 at 12:44:26PM +0200, Greg Kurz wrote:
  On Fri, 24 Apr 2015 15:31:54 +0200
  Michael S. Tsirkin m...@redhat.com wrote:
  
   On Fri, Apr 24, 2015 at 02:24:15PM +0200, Greg Kurz wrote:
Only cosmetic and documentation changes since v5.

---
   
   Looks sane to me. I plan to review and apply next week.
   
  
  Hi Michael,
  
  I realize you just got back and have tons of things to do... Do
  you still plan to apply shortly ? Would you also have time to
  comment the QEMU part ?
  
  Thanks.
  
  --
  Greg
 
 Yes, sorry about the delay - I also got virtio upstream landed on my lap.
 I'll do my best to prioritize.
 

Hi Michael,

This is just a friendly reminder. Are there chances you pick up this
kernel series before virtio 1.0 is in upstream QEMU ?

Cheers.

--
Greg

Greg Kurz (8):
  virtio: introduce virtio_is_little_endian() helper
  tun: add tun_is_little_endian() helper
  macvtap: introduce macvtap_is_little_endian() helper
  vringh: introduce vringh_is_little_endian() helper
  vhost: introduce vhost_is_little_endian() helper
  virtio: add explicit big-endian support to memory accessors
  vhost: cross-endian support for legacy devices
  macvtap/tun: cross-endian support for little-endian hosts


 drivers/net/Kconfig  |   14 ++
 drivers/net/macvtap.c|   66 +-
 drivers/net/tun.c|   68 ++
 drivers/vhost/Kconfig|   15 +++
 drivers/vhost/vhost.c|   85 
++
 drivers/vhost/vhost.h|   25 ---
 include/linux/virtio_byteorder.h |   24 ++-
 include/linux/virtio_config.h|   18 +---
 include/linux/vringh.h   |   18 +---
 include/uapi/linux/if_tun.h  |6 +++
 include/uapi/linux/vhost.h   |   14 ++
 11 files changed, 320 insertions(+), 33 deletions(-)

--
Greg
   
 

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Re: [PATCH v5 6/8] virtio: add explicit big-endian support to memory accessors

[Greg Kurz]

On Fri, 24 Apr 2015 09:04:21 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:
 On Thu, 23 Apr 2015 21:27:19 +0200
 Thomas Huth th...@redhat.com wrote:
 

Thomas's e-mail did not make it to my mailbox... weird. :-\

  On Thu, 23 Apr 2015 17:29:06 +0200
  Greg Kurz gk...@linux.vnet.ibm.com wrote:
  
   The current memory accessors logic is:
   - little endian if little_endian
   - native endian (i.e. no byteswap) if !little_endian
   
   If we want to fully support cross-endian vhost, we also need to be
   able to convert to big endian.
   
   Instead of changing the little_endian argument to some 3-value enum, this
   patch changes the logic to:
   - little endian if little_endian
   - big endian if !little_endian
   
   The native endian case is handled by all users with a trivial helper. This
   patch doesn't change any functionality, nor it does add overhead.
   
   Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
   ---
   
   Changes since v4:
   - style fixes (I have chosen if ... else in most places to stay below
 80 columns, with the notable exception of the vhost helper which gets
 shorten in a later patch)
   
drivers/net/macvtap.c|5 -
drivers/net/tun.c|5 -
drivers/vhost/vhost.h|2 +-
include/linux/virtio_byteorder.h |   24 ++--
include/linux/virtio_config.h|5 -
include/linux/vringh.h   |2 +-
6 files changed, 28 insertions(+), 15 deletions(-)
   
   diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
   index a2f2958..6cf6b3e 100644
   --- a/drivers/net/macvtap.c
   +++ b/drivers/net/macvtap.c
   @@ -51,7 +51,10 @@ struct macvtap_queue {

static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
{
   - return q-flags  MACVTAP_VNET_LE;
   + if (q-flags  MACVTAP_VNET_LE)
   + return true;
   + else
   + return virtio_legacy_is_little_endian();
  
  simply:
  
  return (q-flags  MACVTAP_VNET_LE) ||
 virtio_legacy_is_little_endian();
  
  ?
 
 ISTR that MST preferred the current notation, but I like either your
 way or ?: (with linebreak) even better.
 

MST did not like the initial notation I had used actually. FWIW I
like the simplicity of Thomas's suggestion... even better than ?:
which is:
 some_LE_check() ? true : some_default_endianness()

  
}

 (...)
   diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
   index 6a49960..954c657 100644
   --- a/drivers/vhost/vhost.h
   +++ b/drivers/vhost/vhost.h
   @@ -175,7 +175,7 @@ static inline bool vhost_has_feature(struct 
   vhost_virtqueue *vq, int bit)

static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
{
   - return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
   + return vhost_has_feature(vq, VIRTIO_F_VERSION_1) ? true : 
   virtio_legacy_is_little_endian();
}
  
  That line is way longer than 80 characters ... may I suggest to switch
  at least here to:
  
  return vhost_has_feature(vq, VIRTIO_F_VERSION_1) ||
 virtio_legacy_is_little_endian();
 
 I think the line will collapse in a further patch anyway.
 

Yes, as mentionned in the changelog :)

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Re: [PATCH v5 7/8] vhost: cross-endian support for legacy devices

[Greg Kurz]

On Fri, 24 Apr 2015 09:19:26 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 On Thu, 23 Apr 2015 17:29:42 +0200
 Greg Kurz gk...@linux.vnet.ibm.com wrote:
 
  This patch brings cross-endian support to vhost when used to implement
  legacy virtio devices. Since it is a relatively rare situation, the
  feature availability is controlled by a kernel config option (not set
  by default).
  
  The vq-is_le boolean field is added to cache the endianness to be
  used for ring accesses. It defaults to native endian, as expected
  by legacy virtio devices. When the ring gets active, we force little
  endian if the device is modern. When the ring is deactivated, we
  revert to the native endian default.
  
  If cross-endian was compiled in, a vq-user_be boolean field is added
  so that userspace may request a specific endianness. This field is
  used to override the default when activating the ring of a legacy
  device. It has no effect on modern devices.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
  
  Changes since v4:
  - rewrote patch title to mention cross-endian
  - renamed config to VHOST_CROSS_ENDIAN_LEGACY
  - rewrote config description and help
  - moved ifdefery to top of vhost.c
  - added a detailed comment about the lifecycle of vq-user_be in
vhost_init_is_le()
  - renamed ioctls to VHOST_[GS]ET_VRING_ENDIAN
  - added LE/BE defines to the ioctl API
  - rewrote ioctl sanity check with the LE/BE defines
  - updated comment in uapi/linux/vhost.h to mention that the availibility
of both SET and GET ioctls depends on the kernel config
  
   drivers/vhost/Kconfig  |   15 
   drivers/vhost/vhost.c  |   86 
  +++-
   drivers/vhost/vhost.h  |   10 +
   include/uapi/linux/vhost.h |   12 ++
   4 files changed, 121 insertions(+), 2 deletions(-)
  
  diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
  index 017a1e8..74d7380 100644
  --- a/drivers/vhost/Kconfig
  +++ b/drivers/vhost/Kconfig
  @@ -32,3 +32,18 @@ config VHOST
  ---help---
This option is selected by any driver which needs to access
the core of vhost.
  +
  +config VHOST_CROSS_ENDIAN_LEGACY
  +   bool Cross-endian support for vhost
  +   default n
  +   ---help---
  + This option allows vhost to support guests with a different byte
  + ordering from host.
 
 ...while using legacy virtio.
 
 Might help to explain the LEGACY in the config option ;)
 

Makes sense indeed !

  +
  + Userspace programs can control the feature using the
  + VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls.
  +
  + This is only useful on a few platforms (ppc64 and arm64). Since it
  + adds some overhead, it is disabled default.
 
 s/default/by default/
 

Ok.

  +
  + If unsure, say N.
  diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
  index 2ee2826..8c4390d 100644
  --- a/drivers/vhost/vhost.c
  +++ b/drivers/vhost/vhost.c
  @@ -36,6 +36,78 @@ enum {
   #define vhost_used_event(vq) ((__virtio16 __user 
  *)vq-avail-ring[vq-num])
   #define vhost_avail_event(vq) ((__virtio16 __user 
  *)vq-used-ring[vq-num])
  
  +#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
  +static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
  +{
  +   vq-user_be = !virtio_legacy_is_little_endian();
  +}
  +
  +static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user 
  *argp)
  +{
  +   struct vhost_vring_state s;
  +
  +   if (vq-private_data)
  +   return -EBUSY;
  +
  +   if (copy_from_user(s, argp, sizeof(s)))
  +   return -EFAULT;
  +
  +   if (s.num != VHOST_VRING_LITTLE_ENDIAN 
  +   s.num != VHOST_VRING_BIG_ENDIAN)
  +   return -EINVAL;
  +
  +   vq-user_be = s.num;
  +
  +   return 0;
  +}
  +
  +static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
  +  int __user *argp)
  +{
  +   struct vhost_vring_state s = {
  +   .index = idx,
  +   .num = vq-user_be
  +   };
  +
  +   if (copy_to_user(argp, s, sizeof(s)))
  +   return -EFAULT;
  +
  +   return 0;
  +}
  +
  +static void vhost_init_is_le(struct vhost_virtqueue *vq)
  +{
  +   /* Note for legacy virtio: user_be is initialized at reset time
  +* according to the host endianness. If userspace does not set an
  +* explicit endianness, the default behavior is native endian, as
  +* expected by legacy virtio.
  +*/
  +   vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
  +}
  +#else
  +static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
  +{
  +   ;
 
 Just leave the function body empty?
 

Ok.

  +}
  +
  +static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user 
  *argp)
  +{
  +   return -ENOIOCTLCMD;
  +}
  +
  +static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
  +  int __user *argp)
  +{
  +   return -ENOIOCTLCMD;
  +}
  +
  +static void

[PATCH v6 5/8] vhost: introduce vhost_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/vhost.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8c1c792..6a49960 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -173,34 +173,39 @@ static inline bool vhost_has_feature(struct 
vhost_virtqueue *vq, int bit)
return vq-acked_features  (1ULL  bit);
 }
 
+static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
+{
+   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
 {
-   return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio16 cpu_to_vhost16(struct vhost_virtqueue *vq, u16 val)
 {
-   return __cpu_to_virtio16(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(vhost_is_little_endian(vq), val);
 }
 
 static inline u32 vhost32_to_cpu(struct vhost_virtqueue *vq, __virtio32 val)
 {
-   return __virtio32_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio32 cpu_to_vhost32(struct vhost_virtqueue *vq, u32 val)
 {
-   return __cpu_to_virtio32(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(vhost_is_little_endian(vq), val);
 }
 
 static inline u64 vhost64_to_cpu(struct vhost_virtqueue *vq, __virtio64 val)
 {
-   return __virtio64_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio64 cpu_to_vhost64(struct vhost_virtqueue *vq, u64 val)
 {
-   return __cpu_to_virtio64(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(vhost_is_little_endian(vq), val);
 }
 #endif

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[PATCH v6 6/8] virtio: add explicit big-endian support to memory accessors

[Greg Kurz]

The current memory accessors logic is:
- little endian if little_endian
- native endian (i.e. no byteswap) if !little_endian

If we want to fully support cross-endian vhost, we also need to be
able to convert to big endian.

Instead of changing the little_endian argument to some 3-value enum, this
patch changes the logic to:
- little endian if little_endian
- big endian if !little_endian

The native endian case is handled by all users with a trivial helper. This
patch doesn't change any functionality, nor it does add overhead.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---

Changes since v5:
- changed endian checking helpers as suggested by Thomas (use || and line
  breaker)

 drivers/net/macvtap.c|3 ++-
 drivers/net/tun.c|3 ++-
 drivers/vhost/vhost.h|3 ++-
 include/linux/virtio_byteorder.h |   24 ++--
 include/linux/virtio_config.h|3 ++-
 include/linux/vringh.h   |3 ++-
 6 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index a2f2958..0327d9d 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -51,7 +51,8 @@ struct macvtap_queue {
 
 static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
 {
-   return q-flags  MACVTAP_VNET_LE;
+   return q-flags  MACVTAP_VNET_LE ||
+   virtio_legacy_is_little_endian();
 }
 
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 3c3d6c0..7c4f6b6 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -208,7 +208,8 @@ struct tun_struct {
 
 static inline bool tun_is_little_endian(struct tun_struct *tun)
 {
-   return tun-flags  TUN_VNET_LE;
+   return tun-flags  TUN_VNET_LE ||
+   virtio_legacy_is_little_endian();
 }
 
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 6a49960..a4fa33a 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -175,7 +175,8 @@ static inline bool vhost_has_feature(struct vhost_virtqueue 
*vq, int bit)
 
 static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
 {
-   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+   return vhost_has_feature(vq, VIRTIO_F_VERSION_1) ||
+   virtio_legacy_is_little_endian();
 }
 
 /* Memory accessors */
diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
index 51865d0..ce63a2c 100644
--- a/include/linux/virtio_byteorder.h
+++ b/include/linux/virtio_byteorder.h
@@ -3,17 +3,21 @@
 #include linux/types.h
 #include uapi/linux/virtio_types.h
 
-/*
- * Low-level memory accessors for handling virtio in modern little endian and 
in
- * compatibility native endian format.
- */
+static inline bool virtio_legacy_is_little_endian(void)
+{
+#ifdef __LITTLE_ENDIAN
+   return true;
+#else
+   return false;
+#endif
+}
 
 static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
 {
if (little_endian)
return le16_to_cpu((__force __le16)val);
else
-   return (__force u16)val;
+   return be16_to_cpu((__force __be16)val);
 }
 
 static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
@@ -21,7 +25,7 @@ static inline __virtio16 __cpu_to_virtio16(bool 
little_endian, u16 val)
if (little_endian)
return (__force __virtio16)cpu_to_le16(val);
else
-   return (__force __virtio16)val;
+   return (__force __virtio16)cpu_to_be16(val);
 }
 
 static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
@@ -29,7 +33,7 @@ static inline u32 __virtio32_to_cpu(bool little_endian, 
__virtio32 val)
if (little_endian)
return le32_to_cpu((__force __le32)val);
else
-   return (__force u32)val;
+   return be32_to_cpu((__force __be32)val);
 }
 
 static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
@@ -37,7 +41,7 @@ static inline __virtio32 __cpu_to_virtio32(bool 
little_endian, u32 val)
if (little_endian)
return (__force __virtio32)cpu_to_le32(val);
else
-   return (__force __virtio32)val;
+   return (__force __virtio32)cpu_to_be32(val);
 }
 
 static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)
@@ -45,7 +49,7 @@ static inline u64 __virtio64_to_cpu(bool little_endian, 
__virtio64 val)
if (little_endian)
return le64_to_cpu((__force __le64)val);
else
-   return (__force u64)val;
+   return be64_to_cpu((__force __be64)val);
 }
 
 static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val)
@@ -53,7 +57,7 @@ static inline __virtio64 __cpu_to_virtio64(bool 
little_endian, u64 val)
if (little_endian)
return

[PATCH v6 3/8] macvtap: introduce macvtap_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/macvtap.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 27ecc5c..a2f2958 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -49,14 +49,19 @@ struct macvtap_queue {
 
 #define MACVTAP_VNET_LE 0x8000
 
+static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
+{
+   return q-flags  MACVTAP_VNET_LE;
+}
+
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
 {
-   return __virtio16_to_cpu(q-flags  MACVTAP_VNET_LE, val);
+   return __virtio16_to_cpu(macvtap_is_little_endian(q), val);
 }
 
 static inline __virtio16 cpu_to_macvtap16(struct macvtap_queue *q, u16 val)
 {
-   return __cpu_to_virtio16(q-flags  MACVTAP_VNET_LE, val);
+   return __cpu_to_virtio16(macvtap_is_little_endian(q), val);
 }
 
 static struct proto macvtap_proto = {

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[PATCH v6 4/8] vringh: introduce vringh_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/vringh.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index a3fa537..3ed62ef 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -226,33 +226,38 @@ static inline void vringh_notify(struct vringh *vrh)
vrh-notify(vrh);
 }
 
+static inline bool vringh_is_little_endian(const struct vringh *vrh)
+{
+   return vrh-little_endian;
+}
+
 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
 {
-   return __virtio16_to_cpu(vrh-little_endian, val);
+   return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
 {
-   return __cpu_to_virtio16(vrh-little_endian, val);
+   return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
 }
 
 static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
 {
-   return __virtio32_to_cpu(vrh-little_endian, val);
+   return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
 {
-   return __cpu_to_virtio32(vrh-little_endian, val);
+   return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
 }
 
 static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
 {
-   return __virtio64_to_cpu(vrh-little_endian, val);
+   return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
 {
-   return __cpu_to_virtio64(vrh-little_endian, val);
+   return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
 }
 #endif /* _LINUX_VRINGH_H */

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[PATCH v6 1/8] virtio: introduce virtio_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/virtio_config.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index ca3ed78..bd1a582 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -205,35 +205,40 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)
return 0;
 }
 
+static inline bool virtio_is_little_endian(struct virtio_device *vdev)
+{
+   return virtio_has_feature(vdev, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
 {
-   return __virtio16_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
 {
-   return __cpu_to_virtio16(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(virtio_is_little_endian(vdev), val);
 }
 
 static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
 {
-   return __virtio32_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
 {
-   return __cpu_to_virtio32(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(virtio_is_little_endian(vdev), val);
 }
 
 static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
 {
-   return __virtio64_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 {
-   return __cpu_to_virtio64(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
 }
 
 /* Config space accessors. */

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[PATCH v6 8/8] macvtap/tun: cross-endian support for little-endian hosts

[Greg Kurz]

The VNET_LE flag was introduced to fix accesses to virtio 1.0 headers
that are always little-endian. It can also be used to handle the special
case of a legacy little-endian device implemented by a big-endian host.

Let's add a flag and ioctls for big-endian devices as well. If both flags
are set, little-endian wins.

Since this is isn't a common usecase, the feature is controlled by a kernel
config option (not set by default).

Both macvtap and tun are covered by this patch since they share the same
API with userland.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---

Changes since v5:
- changed {macvtapi,tun}_legacy_is_little_endian() to use ?:

 drivers/net/Kconfig |   14 ++
 drivers/net/macvtap.c   |   57 +-
 drivers/net/tun.c   |   59 ++-
 include/uapi/linux/if_tun.h |6 
 4 files changed, 134 insertions(+), 2 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index df51d60..71ac0ec 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -244,6 +244,20 @@ config TUN
 
  If you don't know what to use this for, you don't need it.
 
+config TUN_VNET_CROSS_LE
+   bool Support for cross-endian vnet headers on little-endian kernels
+   default n
+   ---help---
+ This option allows TUN/TAP and MACVTAP device drivers in a
+ little-endian kernel to parse vnet headers that come from a
+ big-endian legacy virtio device.
+
+ Userspace programs can control the feature using the TUNSETVNETBE
+ and TUNGETVNETBE ioctls.
+
+ Unless you have a little-endian system hosting a big-endian virtual
+ machine with a legacy virtio NIC, you should say N.
+
 config VETH
tristate Virtual ethernet pair device
---help---
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 0327d9d..dc0a47c 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -48,11 +48,60 @@ struct macvtap_queue {
 #define MACVTAP_FEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
 
 #define MACVTAP_VNET_LE 0x8000
+#define MACVTAP_VNET_BE 0x4000
+
+#ifdef CONFIG_TUN_VNET_CROSS_LE
+static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
+{
+   return q-flags  MACVTAP_VNET_BE ? false :
+   virtio_legacy_is_little_endian();
+}
+
+static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *sp)
+{
+   int s = !!(q-flags  MACVTAP_VNET_BE);
+
+   if (put_user(s, sp))
+   return -EFAULT;
+
+   return 0;
+}
+
+static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *sp)
+{
+   int s;
+
+   if (get_user(s, sp))
+   return -EFAULT;
+
+   if (s)
+   q-flags |= MACVTAP_VNET_BE;
+   else
+   q-flags = ~MACVTAP_VNET_BE;
+
+   return 0;
+}
+#else
+static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
+{
+   return virtio_legacy_is_little_endian();
+}
+
+static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *argp)
+{
+   return -EINVAL;
+}
+
+static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *argp)
+{
+   return -EINVAL;
+}
+#endif /* CONFIG_TUN_VNET_CROSS_LE */
 
 static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
 {
return q-flags  MACVTAP_VNET_LE ||
-   virtio_legacy_is_little_endian();
+   macvtap_legacy_is_little_endian(q);
 }
 
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
@@ -1096,6 +1145,12 @@ static long macvtap_ioctl(struct file *file, unsigned 
int cmd,
q-flags = ~MACVTAP_VNET_LE;
return 0;
 
+   case TUNGETVNETBE:
+   return macvtap_get_vnet_be(q, sp);
+
+   case TUNSETVNETBE:
+   return macvtap_set_vnet_be(q, sp);
+
case TUNSETOFFLOAD:
/* let the user check for future flags */
if (arg  ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7c4f6b6..9fa05d6 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -111,6 +111,7 @@ do {
\
 #define TUN_FASYNC IFF_ATTACH_QUEUE
 /* High bits in flags field are unused. */
 #define TUN_VNET_LE 0x8000
+#define TUN_VNET_BE 0x4000
 
 #define TUN_FEATURES (IFF_NO_PI | IFF_ONE_QUEUE | IFF_VNET_HDR | \
  IFF_MULTI_QUEUE)
@@ -206,10 +207,58 @@ struct tun_struct {
u32 flow_count;
 };
 
+#ifdef CONFIG_TUN_VNET_CROSS_LE
+static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
+{
+   return tun-flags  TUN_VNET_BE ? false :
+   virtio_legacy_is_little_endian();
+}
+
+static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+   int be = !!(tun-flags  TUN_VNET_BE);
+
+   if (put_user

[PATCH v6 2/8] tun: add tun_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/tun.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 857dca4..3c3d6c0 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -206,14 +206,19 @@ struct tun_struct {
u32 flow_count;
 };
 
+static inline bool tun_is_little_endian(struct tun_struct *tun)
+{
+   return tun-flags  TUN_VNET_LE;
+}
+
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
 {
-   return __virtio16_to_cpu(tun-flags  TUN_VNET_LE, val);
+   return __virtio16_to_cpu(tun_is_little_endian(tun), val);
 }
 
 static inline __virtio16 cpu_to_tun16(struct tun_struct *tun, u16 val)
 {
-   return __cpu_to_virtio16(tun-flags  TUN_VNET_LE, val);
+   return __cpu_to_virtio16(tun_is_little_endian(tun), val);
 }
 
 static inline u32 tun_hashfn(u32 rxhash)

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[PATCH v6 7/8] vhost: cross-endian support for legacy devices

[Greg Kurz]

This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the
feature availability is controlled by a kernel config option (not set
by default).

The vq-is_le boolean field is added to cache the endianness to be
used for ring accesses. It defaults to native endian, as expected
by legacy virtio devices. When the ring gets active, we force little
endian if the device is modern. When the ring is deactivated, we
revert to the native endian default.

If cross-endian was compiled in, a vq-user_be boolean field is added
so that userspace may request a specific endianness. This field is
used to override the default when activating the ring of a legacy
device. It has no effect on modern devices.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---

Changes since v5:
- fixed description in Kconfig
- fixed error description in uapi header
- dropped useless semi-colon in the vhost_vq_reset_user_be() stub

 drivers/vhost/Kconfig  |   15 
 drivers/vhost/vhost.c  |   85 +++-
 drivers/vhost/vhost.h  |   11 +-
 include/uapi/linux/vhost.h |   14 +++
 4 files changed, 122 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 017a1e8..533eaf0 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -32,3 +32,18 @@ config VHOST
---help---
  This option is selected by any driver which needs to access
  the core of vhost.
+
+config VHOST_CROSS_ENDIAN_LEGACY
+   bool Cross-endian support for vhost
+   default n
+   ---help---
+ This option allows vhost to support guests with a different byte
+ ordering from host while using legacy virtio.
+
+ Userspace programs can control the feature using the
+ VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls.
+
+ This is only useful on a few platforms (ppc64 and arm64). Since it
+ adds some overhead, it is disabled by default.
+
+ If unsure, say N.
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..9e8e004 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -36,6 +36,77 @@ enum {
 #define vhost_used_event(vq) ((__virtio16 __user *)vq-avail-ring[vq-num])
 #define vhost_avail_event(vq) ((__virtio16 __user *)vq-used-ring[vq-num])
 
+#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+   vq-user_be = !virtio_legacy_is_little_endian();
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user 
*argp)
+{
+   struct vhost_vring_state s;
+
+   if (vq-private_data)
+   return -EBUSY;
+
+   if (copy_from_user(s, argp, sizeof(s)))
+   return -EFAULT;
+
+   if (s.num != VHOST_VRING_LITTLE_ENDIAN 
+   s.num != VHOST_VRING_BIG_ENDIAN)
+   return -EINVAL;
+
+   vq-user_be = s.num;
+
+   return 0;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+  int __user *argp)
+{
+   struct vhost_vring_state s = {
+   .index = idx,
+   .num = vq-user_be
+   };
+
+   if (copy_to_user(argp, s, sizeof(s)))
+   return -EFAULT;
+
+   return 0;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+   /* Note for legacy virtio: user_be is initialized at reset time
+* according to the host endianness. If userspace does not set an
+* explicit endianness, the default behavior is native endian, as
+* expected by legacy virtio.
+*/
+   vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
+}
+#else
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user 
*argp)
+{
+   return -ENOIOCTLCMD;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+  int __user *argp)
+{
+   return -ENOIOCTLCMD;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+   vq-is_le = true;
+}
+#endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
+
 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
 {
@@ -199,6 +270,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq-call = NULL;
vq-log_ctx = NULL;
vq-memory = NULL;
+   vq-is_le = virtio_legacy_is_little_endian();
+   vhost_vq_reset_user_be(vq);
 }
 
 static int vhost_worker(void *data)
@@ -806,6 +879,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, 
void __user *argp)
} else
filep = eventfp;
break;
+   case VHOST_SET_VRING_ENDIAN:
+   r

[PATCH v6 0/8] vhost: support for cross endian guests

[Greg Kurz]

Only cosmetic and documentation changes since v5.

---

Greg Kurz (8):
  virtio: introduce virtio_is_little_endian() helper
  tun: add tun_is_little_endian() helper
  macvtap: introduce macvtap_is_little_endian() helper
  vringh: introduce vringh_is_little_endian() helper
  vhost: introduce vhost_is_little_endian() helper
  virtio: add explicit big-endian support to memory accessors
  vhost: cross-endian support for legacy devices
  macvtap/tun: cross-endian support for little-endian hosts


 drivers/net/Kconfig  |   14 ++
 drivers/net/macvtap.c|   66 +-
 drivers/net/tun.c|   68 ++
 drivers/vhost/Kconfig|   15 +++
 drivers/vhost/vhost.c|   85 ++
 drivers/vhost/vhost.h|   25 ---
 include/linux/virtio_byteorder.h |   24 ++-
 include/linux/virtio_config.h|   18 +---
 include/linux/vringh.h   |   18 +---
 include/uapi/linux/if_tun.h  |6 +++
 include/uapi/linux/vhost.h   |   14 ++
 11 files changed, 320 insertions(+), 33 deletions(-)

--
Greg

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[PATCH v5 2/8] tun: add tun_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/tun.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 857dca4..3c3d6c0 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -206,14 +206,19 @@ struct tun_struct {
u32 flow_count;
 };
 
+static inline bool tun_is_little_endian(struct tun_struct *tun)
+{
+   return tun-flags  TUN_VNET_LE;
+}
+
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
 {
-   return __virtio16_to_cpu(tun-flags  TUN_VNET_LE, val);
+   return __virtio16_to_cpu(tun_is_little_endian(tun), val);
 }
 
 static inline __virtio16 cpu_to_tun16(struct tun_struct *tun, u16 val)
 {
-   return __cpu_to_virtio16(tun-flags  TUN_VNET_LE, val);
+   return __cpu_to_virtio16(tun_is_little_endian(tun), val);
 }
 
 static inline u32 tun_hashfn(u32 rxhash)

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[PATCH v5 3/8] macvtap: introduce macvtap_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/macvtap.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 27ecc5c..a2f2958 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -49,14 +49,19 @@ struct macvtap_queue {
 
 #define MACVTAP_VNET_LE 0x8000
 
+static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
+{
+   return q-flags  MACVTAP_VNET_LE;
+}
+
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
 {
-   return __virtio16_to_cpu(q-flags  MACVTAP_VNET_LE, val);
+   return __virtio16_to_cpu(macvtap_is_little_endian(q), val);
 }
 
 static inline __virtio16 cpu_to_macvtap16(struct macvtap_queue *q, u16 val)
 {
-   return __cpu_to_virtio16(q-flags  MACVTAP_VNET_LE, val);
+   return __cpu_to_virtio16(macvtap_is_little_endian(q), val);
 }
 
 static struct proto macvtap_proto = {

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[PATCH v5 4/8] vringh: introduce vringh_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/vringh.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index a3fa537..3ed62ef 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -226,33 +226,38 @@ static inline void vringh_notify(struct vringh *vrh)
vrh-notify(vrh);
 }
 
+static inline bool vringh_is_little_endian(const struct vringh *vrh)
+{
+   return vrh-little_endian;
+}
+
 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
 {
-   return __virtio16_to_cpu(vrh-little_endian, val);
+   return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
 {
-   return __cpu_to_virtio16(vrh-little_endian, val);
+   return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
 }
 
 static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
 {
-   return __virtio32_to_cpu(vrh-little_endian, val);
+   return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
 {
-   return __cpu_to_virtio32(vrh-little_endian, val);
+   return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
 }
 
 static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
 {
-   return __virtio64_to_cpu(vrh-little_endian, val);
+   return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
 {
-   return __cpu_to_virtio64(vrh-little_endian, val);
+   return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
 }
 #endif /* _LINUX_VRINGH_H */

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[PATCH v5 5/8] vhost: introduce vhost_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/vhost.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8c1c792..6a49960 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -173,34 +173,39 @@ static inline bool vhost_has_feature(struct 
vhost_virtqueue *vq, int bit)
return vq-acked_features  (1ULL  bit);
 }
 
+static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
+{
+   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
 {
-   return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio16 cpu_to_vhost16(struct vhost_virtqueue *vq, u16 val)
 {
-   return __cpu_to_virtio16(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(vhost_is_little_endian(vq), val);
 }
 
 static inline u32 vhost32_to_cpu(struct vhost_virtqueue *vq, __virtio32 val)
 {
-   return __virtio32_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio32 cpu_to_vhost32(struct vhost_virtqueue *vq, u32 val)
 {
-   return __cpu_to_virtio32(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(vhost_is_little_endian(vq), val);
 }
 
 static inline u64 vhost64_to_cpu(struct vhost_virtqueue *vq, __virtio64 val)
 {
-   return __virtio64_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio64 cpu_to_vhost64(struct vhost_virtqueue *vq, u64 val)
 {
-   return __cpu_to_virtio64(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(vhost_is_little_endian(vq), val);
 }
 #endif

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[PATCH v5 1/8] virtio: introduce virtio_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/virtio_config.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index ca3ed78..bd1a582 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -205,35 +205,40 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)
return 0;
 }
 
+static inline bool virtio_is_little_endian(struct virtio_device *vdev)
+{
+   return virtio_has_feature(vdev, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
 {
-   return __virtio16_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
 {
-   return __cpu_to_virtio16(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(virtio_is_little_endian(vdev), val);
 }
 
 static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
 {
-   return __virtio32_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
 {
-   return __cpu_to_virtio32(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(virtio_is_little_endian(vdev), val);
 }
 
 static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
 {
-   return __virtio64_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 {
-   return __cpu_to_virtio64(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
 }
 
 /* Config space accessors. */

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[PATCH v5 0/8] vhost: support for cross endian guests

[Greg Kurz]

Hi,

This patchset allows vhost to be used with legacy virtio when guest and host
have a different endianness. It is compatible with modern virtio and can be
fully compiled out through kernel config.

FWIW, I could flawlessly kexec/reboot guests from ppc64 to ppc64le and back.
I could also migrate from a ppc64 to a ppc64le host and back. No regressions
on x86 as expected. My experimental QEMU tree is here:

https://github.com/gkurz/qemu.git vhost/cross-endian

I'd be glad if this series could make it to 4.1.

Cheers.

---

Greg Kurz (8):
  virtio: introduce virtio_is_little_endian() helper
  tun: add tun_is_little_endian() helper
  macvtap: introduce macvtap_is_little_endian() helper
  vringh: introduce vringh_is_little_endian() helper
  vhost: introduce vhost_is_little_endian() helper
  virtio: add explicit big-endian support to memory accessors
  vhost: cross-endian support for legacy devices
  macvtap/tun: cross-endian support for little-endian hosts


 drivers/net/Kconfig  |   14 ++
 drivers/net/macvtap.c|   68 +-
 drivers/net/tun.c|   70 ++-
 drivers/vhost/Kconfig|   15 +++
 drivers/vhost/vhost.c|   86 ++
 drivers/vhost/vhost.h|   25 ---
 include/linux/virtio_byteorder.h |   24 ++-
 include/linux/virtio_config.h|   20 ++---
 include/linux/vringh.h   |   17 +---
 include/uapi/linux/if_tun.h  |6 +++
 include/uapi/linux/vhost.h   |   12 +
 11 files changed, 324 insertions(+), 33 deletions(-)

--
Greg

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[PATCH v5 6/8] virtio: add explicit big-endian support to memory accessors

[Greg Kurz]

The current memory accessors logic is:
- little endian if little_endian
- native endian (i.e. no byteswap) if !little_endian

If we want to fully support cross-endian vhost, we also need to be
able to convert to big endian.

Instead of changing the little_endian argument to some 3-value enum, this
patch changes the logic to:
- little endian if little_endian
- big endian if !little_endian

The native endian case is handled by all users with a trivial helper. This
patch doesn't change any functionality, nor it does add overhead.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---

Changes since v4:
- style fixes (I have chosen if ... else in most places to stay below
  80 columns, with the notable exception of the vhost helper which gets
  shorten in a later patch)

 drivers/net/macvtap.c|5 -
 drivers/net/tun.c|5 -
 drivers/vhost/vhost.h|2 +-
 include/linux/virtio_byteorder.h |   24 ++--
 include/linux/virtio_config.h|5 -
 include/linux/vringh.h   |2 +-
 6 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index a2f2958..6cf6b3e 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -51,7 +51,10 @@ struct macvtap_queue {
 
 static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
 {
-   return q-flags  MACVTAP_VNET_LE;
+   if (q-flags  MACVTAP_VNET_LE)
+   return true;
+   else
+   return virtio_legacy_is_little_endian();
 }
 
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 3c3d6c0..5b044d4 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -208,7 +208,10 @@ struct tun_struct {
 
 static inline bool tun_is_little_endian(struct tun_struct *tun)
 {
-   return tun-flags  TUN_VNET_LE;
+   if (tun-flags  TUN_VNET_LE)
+   return true;
+   else
+   return virtio_legacy_is_little_endian();
 }
 
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 6a49960..954c657 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -175,7 +175,7 @@ static inline bool vhost_has_feature(struct vhost_virtqueue 
*vq, int bit)
 
 static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
 {
-   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+   return vhost_has_feature(vq, VIRTIO_F_VERSION_1) ? true : 
virtio_legacy_is_little_endian();
 }
 
 /* Memory accessors */
diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
index 51865d0..ce63a2c 100644
--- a/include/linux/virtio_byteorder.h
+++ b/include/linux/virtio_byteorder.h
@@ -3,17 +3,21 @@
 #include linux/types.h
 #include uapi/linux/virtio_types.h
 
-/*
- * Low-level memory accessors for handling virtio in modern little endian and 
in
- * compatibility native endian format.
- */
+static inline bool virtio_legacy_is_little_endian(void)
+{
+#ifdef __LITTLE_ENDIAN
+   return true;
+#else
+   return false;
+#endif
+}
 
 static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
 {
if (little_endian)
return le16_to_cpu((__force __le16)val);
else
-   return (__force u16)val;
+   return be16_to_cpu((__force __be16)val);
 }
 
 static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
@@ -21,7 +25,7 @@ static inline __virtio16 __cpu_to_virtio16(bool 
little_endian, u16 val)
if (little_endian)
return (__force __virtio16)cpu_to_le16(val);
else
-   return (__force __virtio16)val;
+   return (__force __virtio16)cpu_to_be16(val);
 }
 
 static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
@@ -29,7 +33,7 @@ static inline u32 __virtio32_to_cpu(bool little_endian, 
__virtio32 val)
if (little_endian)
return le32_to_cpu((__force __le32)val);
else
-   return (__force u32)val;
+   return be32_to_cpu((__force __be32)val);
 }
 
 static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
@@ -37,7 +41,7 @@ static inline __virtio32 __cpu_to_virtio32(bool 
little_endian, u32 val)
if (little_endian)
return (__force __virtio32)cpu_to_le32(val);
else
-   return (__force __virtio32)val;
+   return (__force __virtio32)cpu_to_be32(val);
 }
 
 static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)
@@ -45,7 +49,7 @@ static inline u64 __virtio64_to_cpu(bool little_endian, 
__virtio64 val)
if (little_endian)
return le64_to_cpu((__force __le64)val);
else
-   return (__force u64)val;
+   return be64_to_cpu((__force __be64)val);
 }
 
 static inline __virtio64 __cpu_to_virtio64

[PATCH v5 8/8] macvtap/tun: cross-endian support for little-endian hosts

[Greg Kurz]

The VNET_LE flag was introduced to fix accesses to virtio 1.0 headers
that are always little-endian. It can also be used to handle the special
case of a legacy little-endian device implemented by a big-endian host.

Let's add a flag and ioctls for big-endian devices as well. If both flags
are set, little-endian wins.

Since this is isn't a common usecase, the feature is controlled by a kernel
config option (not set by default).

Both macvtap and tun are covered by this patch since they share the same
API with userland.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---

Changes since v4:
- rewrote patch title to mention cross-endian
- renamed config to TUN_VNET_CROSS_LE
- rewrote config description and help
- moved ifdefery to top of tun.c and macvtap.c
- updated comment in uapi/linux/if_tun.h to mention that the availibility
  of both SET and GET ioctls depends on the kernel config

 drivers/net/Kconfig |   14 ++
 drivers/net/macvtap.c   |   58 +-
 drivers/net/tun.c   |   60 ++-
 include/uapi/linux/if_tun.h |6 
 4 files changed, 136 insertions(+), 2 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index df51d60..71ac0ec 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -244,6 +244,20 @@ config TUN
 
  If you don't know what to use this for, you don't need it.
 
+config TUN_VNET_CROSS_LE
+   bool Support for cross-endian vnet headers on little-endian kernels
+   default n
+   ---help---
+ This option allows TUN/TAP and MACVTAP device drivers in a
+ little-endian kernel to parse vnet headers that come from a
+ big-endian legacy virtio device.
+
+ Userspace programs can control the feature using the TUNSETVNETBE
+ and TUNGETVNETBE ioctls.
+
+ Unless you have a little-endian system hosting a big-endian virtual
+ machine with a legacy virtio NIC, you should say N.
+
 config VETH
tristate Virtual ethernet pair device
---help---
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 6cf6b3e..460ed9f 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -48,13 +48,63 @@ struct macvtap_queue {
 #define MACVTAP_FEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
 
 #define MACVTAP_VNET_LE 0x8000
+#define MACVTAP_VNET_BE 0x4000
+
+#ifdef CONFIG_TUN_VNET_CROSS_LE
+static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
+{
+   if (q-flags  MACVTAP_VNET_BE)
+   return false;
+   return virtio_legacy_is_little_endian();
+}
+
+static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *sp)
+{
+   int s = !!(q-flags  MACVTAP_VNET_BE);
+
+   if (put_user(s, sp))
+   return -EFAULT;
+
+   return 0;
+}
+
+static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *sp)
+{
+   int s;
+
+   if (get_user(s, sp))
+   return -EFAULT;
+
+   if (s)
+   q-flags |= MACVTAP_VNET_BE;
+   else
+   q-flags = ~MACVTAP_VNET_BE;
+
+   return 0;
+}
+#else
+static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
+{
+   return virtio_legacy_is_little_endian();
+}
+
+static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *argp)
+{
+   return -EINVAL;
+}
+
+static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *argp)
+{
+   return -EINVAL;
+}
+#endif /* CONFIG_TUN_VNET_CROSS_LE */
 
 static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
 {
if (q-flags  MACVTAP_VNET_LE)
return true;
else
-   return virtio_legacy_is_little_endian();
+   return macvtap_legacy_is_little_endian(q);
 }
 
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
@@ -1098,6 +1148,12 @@ static long macvtap_ioctl(struct file *file, unsigned 
int cmd,
q-flags = ~MACVTAP_VNET_LE;
return 0;
 
+   case TUNGETVNETBE:
+   return macvtap_get_vnet_be(q, sp);
+
+   case TUNSETVNETBE:
+   return macvtap_set_vnet_be(q, sp);
+
case TUNSETOFFLOAD:
/* let the user check for future flags */
if (arg  ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 5b044d4..1b0afa9 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -111,6 +111,7 @@ do {
\
 #define TUN_FASYNC IFF_ATTACH_QUEUE
 /* High bits in flags field are unused. */
 #define TUN_VNET_LE 0x8000
+#define TUN_VNET_BE 0x4000
 
 #define TUN_FEATURES (IFF_NO_PI | IFF_ONE_QUEUE | IFF_VNET_HDR | \
  IFF_MULTI_QUEUE)
@@ -206,12 +207,61 @@ struct tun_struct {
u32 flow_count;
 };
 
+#ifdef CONFIG_TUN_VNET_CROSS_LE
+static inline

[PATCH v5 7/8] vhost: cross-endian support for legacy devices

[Greg Kurz]

This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the
feature availability is controlled by a kernel config option (not set
by default).

The vq-is_le boolean field is added to cache the endianness to be
used for ring accesses. It defaults to native endian, as expected
by legacy virtio devices. When the ring gets active, we force little
endian if the device is modern. When the ring is deactivated, we
revert to the native endian default.

If cross-endian was compiled in, a vq-user_be boolean field is added
so that userspace may request a specific endianness. This field is
used to override the default when activating the ring of a legacy
device. It has no effect on modern devices.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---

Changes since v4:
- rewrote patch title to mention cross-endian
- renamed config to VHOST_CROSS_ENDIAN_LEGACY
- rewrote config description and help
- moved ifdefery to top of vhost.c
- added a detailed comment about the lifecycle of vq-user_be in
  vhost_init_is_le()
- renamed ioctls to VHOST_[GS]ET_VRING_ENDIAN
- added LE/BE defines to the ioctl API
- rewrote ioctl sanity check with the LE/BE defines
- updated comment in uapi/linux/vhost.h to mention that the availibility
  of both SET and GET ioctls depends on the kernel config

 drivers/vhost/Kconfig  |   15 
 drivers/vhost/vhost.c  |   86 +++-
 drivers/vhost/vhost.h  |   10 +
 include/uapi/linux/vhost.h |   12 ++
 4 files changed, 121 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 017a1e8..74d7380 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -32,3 +32,18 @@ config VHOST
---help---
  This option is selected by any driver which needs to access
  the core of vhost.
+
+config VHOST_CROSS_ENDIAN_LEGACY
+   bool Cross-endian support for vhost
+   default n
+   ---help---
+ This option allows vhost to support guests with a different byte
+ ordering from host.
+
+ Userspace programs can control the feature using the
+ VHOST_SET_VRING_ENDIAN and VHOST_GET_VRING_ENDIAN ioctls.
+
+ This is only useful on a few platforms (ppc64 and arm64). Since it
+ adds some overhead, it is disabled default.
+
+ If unsure, say N.
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..8c4390d 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -36,6 +36,78 @@ enum {
 #define vhost_used_event(vq) ((__virtio16 __user *)vq-avail-ring[vq-num])
 #define vhost_avail_event(vq) ((__virtio16 __user *)vq-used-ring[vq-num])
 
+#ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+   vq-user_be = !virtio_legacy_is_little_endian();
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user 
*argp)
+{
+   struct vhost_vring_state s;
+
+   if (vq-private_data)
+   return -EBUSY;
+
+   if (copy_from_user(s, argp, sizeof(s)))
+   return -EFAULT;
+
+   if (s.num != VHOST_VRING_LITTLE_ENDIAN 
+   s.num != VHOST_VRING_BIG_ENDIAN)
+   return -EINVAL;
+
+   vq-user_be = s.num;
+
+   return 0;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+  int __user *argp)
+{
+   struct vhost_vring_state s = {
+   .index = idx,
+   .num = vq-user_be
+   };
+
+   if (copy_to_user(argp, s, sizeof(s)))
+   return -EFAULT;
+
+   return 0;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+   /* Note for legacy virtio: user_be is initialized at reset time
+* according to the host endianness. If userspace does not set an
+* explicit endianness, the default behavior is native endian, as
+* expected by legacy virtio.
+*/
+   vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
+}
+#else
+static void vhost_vq_reset_user_be(struct vhost_virtqueue *vq)
+{
+   ;
+}
+
+static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user 
*argp)
+{
+   return -ENOIOCTLCMD;
+}
+
+static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
+  int __user *argp)
+{
+   return -ENOIOCTLCMD;
+}
+
+static void vhost_init_is_le(struct vhost_virtqueue *vq)
+{
+   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+   vq-is_le = true;
+}
+#endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
+
 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
 {
@@ -199,6 +271,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq-call = NULL;
vq-log_ctx = NULL;
vq-memory = NULL;
+   vq-is_le

Re: [PATCH v4 8/8] macvtap/tun: add VNET_BE flag

[Greg Kurz]

On Tue, 21 Apr 2015 20:30:23 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Tue, Apr 21, 2015 at 06:22:20PM +0200, Greg Kurz wrote:
  On Tue, 21 Apr 2015 16:06:33 +0200
  Michael S. Tsirkin m...@redhat.com wrote:
  
   On Fri, Apr 10, 2015 at 12:20:21PM +0200, Greg Kurz wrote:
The VNET_LE flag was introduced to fix accesses to virtio 1.0 headers
that are always little-endian. It can also be used to handle the special
case of a legacy little-endian device implemented by a big-endian host.

Let's add a flag and ioctls for big-endian devices as well. If both 
flags
are set, little-endian wins.

Since this is isn't a common usecase, the feature is controlled by a 
kernel
config option (not set by default).

Both macvtap and tun are covered by this patch since they share the same
API with userland.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/Kconfig |   12 
 drivers/net/macvtap.c   |   60 
+-
 drivers/net/tun.c   |   62 
++-
 include/uapi/linux/if_tun.h |2 +
 4 files changed, 134 insertions(+), 2 deletions(-)

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index df51d60..f0e23a0 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -244,6 +244,18 @@ config TUN
 
  If you don't know what to use this for, you don't need it.
 
+config TUN_VNET_BE
+   bool Support for big-endian vnet headers
+   default n
+   ---help---
+ This option allows TUN/TAP and MACVTAP device drivers to parse
+ vnet headers that are in big-endian byte order. It is useful
+ when the headers come from a big-endian legacy virtio driver 
and
+ the host is little-endian.
+
+ Unless you have a little-endian system hosting a big-endian 
virtual
+ machine with a virtio NIC, you should say N.
+
   
   should mention cross-endian, not big-endian, right?
   
  
  The current TUN_VNET_LE related code is already doing cross-endian: without
  this patch, one can already run a LE guest on a BE host... wouldn't it be
  confusing to mention cross-endian only when the guest is BE ?
 
 Hmm I think no - LE is also useful for virtio 1 - this is what it was
 intended for after all.
 
  What about having a completely distinct implementation for cross-endian that
  don't reuse the existing code and defines then ?
 
 I think implementation and interface are fine, just the documentation
 can be improved a bit.
 
 How about:
   Support for cross-endian vnet headers on little-endian kernels.
 
 Accordingly CONFIG_TUN_VNET_CROSS_LE
 
 ?
 

Sure. And what about also renaming the ioctl to TUNSETVNETCROSSLE then ?

--
Greg

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Re: [PATCH v4 7/8] vhost: feature to set the vring endianness

[Greg Kurz]

On Tue, 21 Apr 2015 20:25:03 +0200
Michael S. Tsirkin m...@redhat.com wrote:
[ ... ]
@@ -630,6 +634,53 @@ static long vhost_set_memory(struct vhost_dev *d, 
struct vhost_memory __user *m)
return 0;
 }
 
+#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
+static long vhost_set_vring_big_endian(struct vhost_virtqueue *vq,
+  int __user *argp)
+{
+   struct vhost_vring_state s;
+
+   if (vq-private_data)
+   return -EBUSY;
+
+   if (copy_from_user(s, argp, sizeof(s)))
+   return -EFAULT;
+
+   if (s.num  s.num != 1)
   
   s.num  ~0x1
   
  
  Since s.num is unsigned and I assume this won't change, what about
  s.num  1 as suggested by Cornelia ?
 
 I just tried and gcc optimizes
 s.num != 0  s.num != 1 to s.num  1
 
 The former will be more readable once we
 replace 0 and 1 with defines.
 
 So ignore my advice, keep code as is but use defines.
 

Ok.

[ ... ] 
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -103,6 +103,15 @@ struct vhost_memory {
 /* Get accessor: reads index, writes value in num */
 #define VHOST_GET_VRING_BASE _IOWR(VHOST_VIRTIO, 0x12, struct 
vhost_vring_state)
 
+/* Set the vring byte order in num. This is a legacy only API that is 
simply
+ * ignored when VIRTIO_F_VERSION_1 is set.
+ * 0 to set to little-endian
+ * 1 to set to big-endian
   
   How about defines for these?
   
  
  Ok. I'll put the defines here so that all the cross-endian stuff
  lies in the same hunk. Is it ok for you ?
 
 Fine.
 
+ * other values return EINVAL.
 
 Pls also add a note saying that not all kernel configurations support this 
 ioctl,
 but all configurations that support SET also support GET.
 

Ok.

+ */
+#define VHOST_SET_VRING_BIG_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct 
vhost_vring_state)
+#define VHOST_GET_VRING_BIG_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct 
vhost_vring_state)
+
 /* The following ioctls use eventfd file descriptors to signal and poll
  * for events. */
 
   
 
 I'm inclined to think VHOST_SET_VRING_ENDIAN is a slightly better name.
 What do you think?
 

Or VHOST_SET_VRING_CROSS_ENDIAN ? I like the idea to keep a hint that this
API is for cross-endian only... like the rest of this series.

--
Greg

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Re: [PATCH v4 0/8] vhost: support for cross endian guests

[Greg Kurz]

On Fri, 17 Apr 2015 11:18:13 +0200
Greg Kurz gk...@linux.vnet.ibm.com wrote:
 On Fri, 10 Apr 2015 12:15:00 +0200
 Greg Kurz gk...@linux.vnet.ibm.com wrote:
 
  Hi,
  
  This patchset allows vhost to be used with legacy virtio when guest and host
  have a different endianness.
  
  Patch 7 got rewritten according to Cornelia's and Michael's comments. I have
  also introduced patch 8 that brings BE vnet headers support to tun/macvtap.
  
  This series is enough to have vhost_net working flawlessly. I could
  succesfully reboot guests from ppc64 to ppc64le and vice-versa on ppc64
  and ppc64le hosts.
  
 
 Michael,
 
 I am ready to post v5 with the changes suggested by Cornelia... Do you have 
 any
 extra comments on this v4 ? 
 

Ping ?

 --
 Greg
 
  ---
  
  Greg Kurz (8):
virtio: introduce virtio_is_little_endian() helper
tun: add tun_is_little_endian() helper
macvtap: introduce macvtap_is_little_endian() helper
vringh: introduce vringh_is_little_endian() helper
vhost: introduce vhost_is_little_endian() helper
virtio: add explicit big-endian support to memory accessors
vhost: feature to set the vring endianness
macvtap/tun: add VNET_BE flag
  
  
   drivers/net/Kconfig  |   12 ++
   drivers/net/macvtap.c|   69 ++-
   drivers/net/tun.c|   71 
  +++-
   drivers/vhost/Kconfig|   10 +
   drivers/vhost/vhost.c|   76 
  ++
   drivers/vhost/vhost.h|   25 ++---
   include/linux/virtio_byteorder.h |   24 +++-
   include/linux/virtio_config.h|   19 +++---
   include/linux/vringh.h   |   19 +++---
   include/uapi/linux/if_tun.h  |2 +
   include/uapi/linux/vhost.h   |9 +
   11 files changed, 303 insertions(+), 33 deletions(-)
  
  --
  Greg
  
  ___
  Virtualization mailing list
  virtualizat...@lists.linux-foundation.org
  https://lists.linuxfoundation.org/mailman/listinfo/virtualization
  
 

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Re: [PATCH v3 6/7] virtio: add explicit big-endian support to memory accessors

[Greg Kurz]

On Tue, 7 Apr 2015 17:56:25 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Tue, Apr 07, 2015 at 02:15:52PM +0200, Greg Kurz wrote:
  The current memory accessors logic is:
  - little endian if little_endian
  - native endian (i.e. no byteswap) if !little_endian
  
  If we want to fully support cross-endian vhost, we also need to be
  able to convert to big endian.
  
  Instead of changing the little_endian argument to some 3-value enum, this
  patch changes the logic to:
  - little endian if little_endian
  - big endian if !little_endian
  
  The native endian case is handled by all users with a trivial helper. This
  patch doesn't change any functionality, nor it does add overhead.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
   drivers/net/macvtap.c|4 +++-
   drivers/net/tun.c|4 +++-
   drivers/vhost/vhost.h|4 +++-
   include/linux/virtio_byteorder.h |   24 ++--
   include/linux/virtio_config.h|4 +++-
   include/linux/vringh.h   |4 +++-
   6 files changed, 29 insertions(+), 15 deletions(-)
  
  diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
  index a2f2958..0a03a66 100644
  --- a/drivers/net/macvtap.c
  +++ b/drivers/net/macvtap.c
  @@ -51,7 +51,9 @@ struct macvtap_queue {
   
   static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
   {
  -   return q-flags  MACVTAP_VNET_LE;
  +   if (q-flags  MACVTAP_VNET_LE)
  +   return true;
  +   return virtio_legacy_is_little_endian();
   }
   
   static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
 
 Hmm I'm not sure how well this will work once you
 actually make it dynamic.
 Remains to be seen.
 

Oops I overlooked this mail... FWIW I could reboot/kexec from a ppc64 guest
to ppc64le and back with the following QEMU:

https://github.com/gkurz/qemu/commits/vhost/cross-endian

  diff --git a/drivers/net/tun.c b/drivers/net/tun.c
  index 3c3d6c0..053f9b6 100644
  --- a/drivers/net/tun.c
  +++ b/drivers/net/tun.c
  @@ -208,7 +208,9 @@ struct tun_struct {
   
   static inline bool tun_is_little_endian(struct tun_struct *tun)
   {
  -   return tun-flags  TUN_VNET_LE;
  +   if (tun-flags  TUN_VNET_LE)
  +   return true;
  +   return virtio_legacy_is_little_endian();
   }
   
   static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
  diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
  index 6a49960..4e9a186 100644
  --- a/drivers/vhost/vhost.h
  +++ b/drivers/vhost/vhost.h
  @@ -175,7 +175,9 @@ static inline bool vhost_has_feature(struct 
  vhost_virtqueue *vq, int bit)
   
   static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
   {
  -   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return true;
  +   return virtio_legacy_is_little_endian();
   }
   
   /* Memory accessors */
  diff --git a/include/linux/virtio_byteorder.h 
  b/include/linux/virtio_byteorder.h
  index 51865d0..ce63a2c 100644
  --- a/include/linux/virtio_byteorder.h
  +++ b/include/linux/virtio_byteorder.h
  @@ -3,17 +3,21 @@
   #include linux/types.h
   #include uapi/linux/virtio_types.h
   
  -/*
  - * Low-level memory accessors for handling virtio in modern little endian 
  and in
  - * compatibility native endian format.
  - */
  +static inline bool virtio_legacy_is_little_endian(void)
  +{
  +#ifdef __LITTLE_ENDIAN
  +   return true;
  +#else
  +   return false;
  +#endif
  +}
   
   static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
   {
  if (little_endian)
  return le16_to_cpu((__force __le16)val);
  else
  -   return (__force u16)val;
  +   return be16_to_cpu((__force __be16)val);
   }
   
   static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
  @@ -21,7 +25,7 @@ static inline __virtio16 __cpu_to_virtio16(bool 
  little_endian, u16 val)
  if (little_endian)
  return (__force __virtio16)cpu_to_le16(val);
  else
  -   return (__force __virtio16)val;
  +   return (__force __virtio16)cpu_to_be16(val);
   }
   
   static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
  @@ -29,7 +33,7 @@ static inline u32 __virtio32_to_cpu(bool little_endian, 
  __virtio32 val)
  if (little_endian)
  return le32_to_cpu((__force __le32)val);
  else
  -   return (__force u32)val;
  +   return be32_to_cpu((__force __be32)val);
   }
   
   static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
  @@ -37,7 +41,7 @@ static inline __virtio32 __cpu_to_virtio32(bool 
  little_endian, u32 val)
  if (little_endian)
  return (__force __virtio32)cpu_to_le32(val);
  else
  -   return (__force __virtio32)val;
  +   return (__force __virtio32)cpu_to_be32(val);
   }
   
   static inline u64 __virtio64_to_cpu(bool little_endian

Re: [PATCH v4 7/8] vhost: feature to set the vring endianness

[Greg Kurz]

On Tue, 21 Apr 2015 16:04:23 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Fri, Apr 10, 2015 at 12:19:16PM +0200, Greg Kurz wrote:
  This patch brings cross-endian support to vhost when used to implement
  legacy virtio devices. Since it is a relatively rare situation, the
  feature availability is controlled by a kernel config option (not set
  by default).
  
  The vq-is_le boolean field is added to cache the endianness to be
  used for ring accesses. It defaults to native endian, as expected
  by legacy virtio devices. When the ring gets active, we force little
  endian if the device is modern. When the ring is deactivated, we
  revert to the native endian default.
  
  If cross-endian was compiled in, a vq-user_be boolean field is added
  so that userspace may request a specific endianness. This field is
  used to override the default when activating the ring of a legacy
  device. It has no effect on modern devices.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
   drivers/vhost/Kconfig  |   10 ++the
   drivers/vhost/vhost.c  |   76 
  +++-
   drivers/vhost/vhost.h  |   12 +--
   include/uapi/linux/vhost.h |9 +
   4 files changed, 103 insertions(+), 4 deletions(-)
  
  Changes since v3:
  - VHOST_SET_VRING_ENDIAN_LEGACY ioctl renamed to VHOST_SET_VRING_BIG_ENDIAN
  - ioctl API is now: 0 for le, 1 for be, other values are EINVAL
  - ioctl doesn't filter out modern devices
  - ioctl stubs return ENOIOCTLCMD
  - forbid endianness changes when vring is active
  - logic now handled with vq-is_le and vq-user_be according to device
start/stop as suggested by Michael
  
  diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
  index 017a1e8..0aec88c 100644
  --- a/drivers/vhost/Kconfig
  +++ b/drivers/vhost/Kconfig
  @@ -32,3 +32,13 @@ config VHOST
  ---help---
This option is selected by any driver which needs to access
the core of vhost.
  +
  +config VHOST_SET_ENDIAN_LEGACY
 
 I'd prefer namin this VHOST_CROSS_ENDIAN_LEGACY
 

Yes, makes sense. I'll make sure most of the cross-endian changes are
easy to grep.

  +   bool Cross-endian support for host kernel accelerator
  +   default n
  +   ---help---
  + This option allows vhost to support guests with a different byte
  + ordering from host. It is disabled by default since it adds overhead
  + and it is only needed by a few platforms (powerpc and arm).
 
 and is only useful on a few platforms (powerpc and arm).
 
 it seems to refer to overhead, which is rarely needed.
 needed is a bit too strong, you can always e.g. run virtio
 in userspace.
 

My poor English again... it seems you understood what I wanted to
write though :)

  +
  + If unsure, say N.
  diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
  index 2ee2826..3eb756b 100644the
  --- a/drivers/vhost/vhost.c
  +++ b/drivers/vhost/vhost.c
  @@ -199,6 +199,10 @@ static void vhost_vq_reset(struct vhost_dev *dev,
  vq-call = NULL;
  vq-log_ctx = NULL;
  vq-memory = NULL;
  +   vq-is_le = virtio_legacy_is_little_endian();
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +   vq-user_be = !vq-is_le;
  +#endif
 
 add a wrapper for this too?
 

Will do.

   }
   
   static int vhost_worker(void *data)
  @@ -630,6 +634,53 @@ static long vhost_set_memory(struct vhost_dev *d, 
  struct vhost_memory __user *m)
  return 0;
   }
   
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +static long vhost_set_vring_big_endian(struct vhost_virtqueue *vq,
  +  int __user *argp)
  +{
  +   struct vhost_vring_state s;
  +
  +   if (vq-private_data)
  +   return -EBUSY;
  +
  +   if (copy_from_user(s, argp, sizeof(s)))
  +   return -EFAULT;
  +
  +   if (s.num  s.num != 1)
 
 s.num  ~0x1
 

Since s.num is unsigned and I assume this won't change, what about
s.num  1 as suggested by Cornelia ?

 
  +   return -EINVAL;
  +
  +   vq-user_be = s.num;
  +
  +   return 0;
  +}
  +
  +static long vhost_get_vring_big_endian(struct vhost_virtqueue *vq, u32 idx,
  +  int __user *argp)
  +{
  +   struct vhost_vring_state s = {
  +   .index = idx,
  +   .num = vq-user_be
  +   };
  +
  +   if (copy_to_user(argp, s, sizeof(s)))
  +   return -EFAULT;
  +
  +   return 0;
  +}
  +#else
  +static long vhost_set_vring_big_endian(struct vhost_virtqueue *vq,
  +  int __user *argp)
  +{
  +   return -ENOIOCTLCMD;
  +}
  +
  +static long vhost_get_vring_big_endian(struct vhost_virtqueue *vq, u32 idx,
  +  int __user *argp)
  +{
  +   return -ENOIOCTLCMD;
  +}
  +#endif /* CONFIG_VHOST_SET_ENDIAN_LEGACY */
  +
   long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
   {
  struct file *eventfp, *filep = NULL;
  @@ -806,6 +857,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, 
  void __user *argp

Re: [PATCH v4 6/8] virtio: add explicit big-endian support to memory accessors

[Greg Kurz]

On Tue, 21 Apr 2015 16:09:44 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Fri, Apr 10, 2015 at 12:16:20PM +0200, Greg Kurz wrote:
  The current memory accessors logic is:
  - little endian if little_endian
  - native endian (i.e. no byteswap) if !little_endian
  
  If we want to fully support cross-endian vhost, we also need to be
  able to convert to big endian.
  
  Instead of changing the little_endian argument to some 3-value enum, this
  patch changes the logic to:
  - little endian if little_endian
  - big endian if !little_endian
  
  The native endian case is handled by all users with a trivial helper. This
  patch doesn't change any functionality, nor it does add overhead.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
 
 OK overall. Style comment:
 
   drivers/net/macvtap.c|4 +++-
   drivers/net/tun.c|4 +++-
   drivers/vhost/vhost.h|4 +++-
   include/linux/virtio_byteorder.h |   24 ++--
   include/linux/virtio_config.h|4 +++-
   include/linux/vringh.h   |4 +++-
   6 files changed, 29 insertions(+), 15 deletions(-)
  
  diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
  index a2f2958..0a03a66 100644
  --- a/drivers/net/macvtap.c
  +++ b/drivers/net/macvtap.c
  @@ -51,7 +51,9 @@ struct macvtap_queue {
   
   static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
   {
  -   return q-flags  MACVTAP_VNET_LE;
  +   if (q-flags  MACVTAP_VNET_LE)
  +   return true;
  +   return virtio_legacy_is_little_endian();
   }
   
 
 I'd prefer a bit more symmetry:
 
 + if (q-flags  MACVTAP_VNET_LE)
 + return true;
 + else
 + return virtio_legacy_is_little_endian();
 
 Or better just:
   return (q-flags  MACVTAP_VNET_LE) ? true : 
 virtio_legacy_is_little_endian();
 
 might make line long, but your follow-up patch makes it short again,
 so that's ok.
 

Will do.

 
   static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
  diff --git a/drivers/net/tun.c b/drivers/net/tun.c
  index 3c3d6c0..053f9b6 100644
  --- a/drivers/net/tun.c
  +++ b/drivers/net/tun.c
  @@ -208,7 +208,9 @@ struct tun_struct {
   
   static inline bool tun_is_little_endian(struct tun_struct *tun)
   {
  -   return tun-flags  TUN_VNET_LE;
  +   if (tun-flags  TUN_VNET_LE)
  +   return true;
  +   return virtio_legacy_is_little_endian();
   }
   
   static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
  diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
  index 6a49960..4e9a186 100644
  --- a/drivers/vhost/vhost.h
  +++ b/drivers/vhost/vhost.h
  @@ -175,7 +175,9 @@ static inline bool vhost_has_feature(struct 
  vhost_virtqueue *vq, int bit)
   
   static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
   {
  -   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return true;
  +   return virtio_legacy_is_little_endian();
   }
   
   /* Memory accessors */
  diff --git a/include/linux/virtio_byteorder.h 
  b/include/linux/virtio_byteorder.h
  index 51865d0..ce63a2c 100644
  --- a/include/linux/virtio_byteorder.h
  +++ b/include/linux/virtio_byteorder.h
  @@ -3,17 +3,21 @@
   #include linux/types.h
   #include uapi/linux/virtio_types.h
   
  -/*
  - * Low-level memory accessors for handling virtio in modern little endian 
  and in
  - * compatibility native endian format.
  - */
  +static inline bool virtio_legacy_is_little_endian(void)
  +{
  +#ifdef __LITTLE_ENDIAN
  +   return true;
  +#else
  +   return false;
  +#endif
  +}
   
   static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
   {
  if (little_endian)
  return le16_to_cpu((__force __le16)val);
  else
  -   return (__force u16)val;
  +   return be16_to_cpu((__force __be16)val);
   }
   
   static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
  @@ -21,7 +25,7 @@ static inline __virtio16 __cpu_to_virtio16(bool 
  little_endian, u16 val)
  if (little_endian)
  return (__force __virtio16)cpu_to_le16(val);
  else
  -   return (__force __virtio16)val;
  +   return (__force __virtio16)cpu_to_be16(val);
   }
   
   static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
  @@ -29,7 +33,7 @@ static inline u32 __virtio32_to_cpu(bool little_endian, 
  __virtio32 val)
  if (little_endian)
  return le32_to_cpu((__force __le32)val);
  else
  -   return (__force u32)val;
  +   return be32_to_cpu((__force __be32)val);
   }
   
   static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
  @@ -37,7 +41,7 @@ static inline __virtio32 __cpu_to_virtio32(bool 
  little_endian, u32 val)
  if (little_endian)
  return (__force __virtio32)cpu_to_le32(val);
  else
  -   return (__force __virtio32)val

Re: [PATCH v4 8/8] macvtap/tun: add VNET_BE flag

[Greg Kurz]

On Tue, 21 Apr 2015 16:06:33 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Fri, Apr 10, 2015 at 12:20:21PM +0200, Greg Kurz wrote:
  The VNET_LE flag was introduced to fix accesses to virtio 1.0 headers
  that are always little-endian. It can also be used to handle the special
  case of a legacy little-endian device implemented by a big-endian host.
  
  Let's add a flag and ioctls for big-endian devices as well. If both flags
  are set, little-endian wins.
  
  Since this is isn't a common usecase, the feature is controlled by a kernel
  config option (not set by default).
  
  Both macvtap and tun are covered by this patch since they share the same
  API with userland.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
   drivers/net/Kconfig |   12 
   drivers/net/macvtap.c   |   60 
  +-
   drivers/net/tun.c   |   62 
  ++-
   include/uapi/linux/if_tun.h |2 +
   4 files changed, 134 insertions(+), 2 deletions(-)
  
  diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
  index df51d60..f0e23a0 100644
  --- a/drivers/net/Kconfig
  +++ b/drivers/net/Kconfig
  @@ -244,6 +244,18 @@ config TUN
   
If you don't know what to use this for, you don't need it.
   
  +config TUN_VNET_BE
  +   bool Support for big-endian vnet headers
  +   default n
  +   ---help---
  + This option allows TUN/TAP and MACVTAP device drivers to parse
  + vnet headers that are in big-endian byte order. It is useful
  + when the headers come from a big-endian legacy virtio driver and
  + the host is little-endian.
  +
  + Unless you have a little-endian system hosting a big-endian virtual
  + machine with a virtio NIC, you should say N.
  +
 
 should mention cross-endian, not big-endian, right?
 

The current TUN_VNET_LE related code is already doing cross-endian: without
this patch, one can already run a LE guest on a BE host... wouldn't it be
confusing to mention cross-endian only when the guest is BE ?

What about having a completely distinct implementation for cross-endian that
don't reuse the existing code and defines then ?

   config VETH
  tristate Virtual ethernet pair device
  ---help---
  diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
  index 0a03a66..e0ab1b7 100644
  --- a/drivers/net/macvtap.c
  +++ b/drivers/net/macvtap.c
  @@ -48,12 +48,27 @@ struct macvtap_queue {
   #define MACVTAP_FEATURES (IFF_VNET_HDR | IFF_MULTI_QUEUE)
   
   #define MACVTAP_VNET_LE 0x8000
  +#define MACVTAP_VNET_BE 0x4000
  +
  +#ifdef CONFIG_TUN_VNET_BE
  +static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
  +{
  +   if (q-flags  MACVTAP_VNET_BE)
  +   return false;
  +   return virtio_legacy_is_little_endian();
  +}
  +#else
  +static inline bool macvtap_legacy_is_little_endian(struct macvtap_queue *q)
  +{
  +   return virtio_legacy_is_little_endian();
  +}
  +#endif
   
   static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
   {
  if (q-flags  MACVTAP_VNET_LE)
  return true;
  -   return virtio_legacy_is_little_endian();
  +   return macvtap_legacy_is_little_endian(q);
   }
   
   static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
  @@ -1000,6 +1015,43 @@ static int set_offload(struct macvtap_queue *q, 
  unsigned long arg)
  return 0;
   }
   
  +#ifdef CONFIG_TUN_VNET_BE
  +static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *sp)
  +{
  +   int s = !!(q-flags  MACVTAP_VNET_BE);
  +
  +   if (put_user(s, sp))
  +   return -EFAULT;
  +
  +   return 0;
  +}
  +
  +static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *sp)
  +{
  +   int s;
  +
  +   if (get_user(s, sp))
  +   return -EFAULT;
  +
  +   if (s)
  +   q-flags |= MACVTAP_VNET_BE;
  +   else
  +   q-flags = ~MACVTAP_VNET_BE;
  +
  +   return 0;
  +}
  +#else
  +static long macvtap_get_vnet_be(struct macvtap_queue *q, int __user *argp)
  +{
  +   return -EINVAL;
  +}
  +
  +static long macvtap_set_vnet_be(struct macvtap_queue *q, int __user *argp)
  +{
  +   return -EINVAL;
  +}
  +#endif /* CONFIG_TUN_VNET_BE */
  +
   /*
* provide compatibility with generic tun/tap interface
*/
  @@ -1097,6 +1149,12 @@ static long macvtap_ioctl(struct file *file, 
  unsigned int cmd,
  q-flags = ~MACVTAP_VNET_LE;
  return 0;
   
  +   case TUNGETVNETBE:
  +   return macvtap_get_vnet_be(q, sp);
  +
  +   case TUNSETVNETBE:
  +   return macvtap_set_vnet_be(q, sp);
  +
  case TUNSETOFFLOAD:
  /* let the user check for future flags */
  if (arg  ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
  diff --git a/drivers/net/tun.c b/drivers/net/tun.c
  index 053f9b6..4e12488 100644
  --- a/drivers/net/tun.c
  +++ b/drivers/net/tun.c
  @@ -111,6 +111,7 @@ do

Re: [PATCH v4 0/8] vhost: support for cross endian guests

[Greg Kurz]

On Tue, 21 Apr 2015 16:10:18 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Fri, Apr 10, 2015 at 12:15:00PM +0200, Greg Kurz wrote:
  Hi,
  
  This patchset allows vhost to be used with legacy virtio when guest and host
  have a different endianness.
  
  Patch 7 got rewritten according to Cornelia's and Michael's comments. I have
  also introduced patch 8 that brings BE vnet headers support to tun/macvtap.
  
  This series is enough to have vhost_net working flawlessly. I could
  succesfully reboot guests from ppc64 to ppc64le and vice-versa on ppc64
  and ppc64le hosts.
 
 Looks good overall.
 A couple of style comments.
 
 Thanks!
 

Thanks for your time Michael.

  ---
  
  Greg Kurz (8):
virtio: introduce virtio_is_little_endian() helper
tun: add tun_is_little_endian() helper
macvtap: introduce macvtap_is_little_endian() helper
vringh: introduce vringh_is_little_endian() helper
vhost: introduce vhost_is_little_endian() helper
virtio: add explicit big-endian support to memory accessors
vhost: feature to set the vring endianness
macvtap/tun: add VNET_BE flag
  
  
   drivers/net/Kconfig  |   12 ++
   drivers/net/macvtap.c|   69 ++-
   drivers/net/tun.c|   71 
  +++-
   drivers/vhost/Kconfig|   10 +
   drivers/vhost/vhost.c|   76 
  ++
   drivers/vhost/vhost.h|   25 ++---
   include/linux/virtio_byteorder.h |   24 +++-
   include/linux/virtio_config.h|   19 +++---
   include/linux/vringh.h   |   19 +++---
   include/uapi/linux/if_tun.h  |2 +
   include/uapi/linux/vhost.h   |9 +
   11 files changed, 303 insertions(+), 33 deletions(-)
  
  --
  Greg
 

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Re: [PATCH v4 0/8] vhost: support for cross endian guests

[Greg Kurz]

On Fri, 10 Apr 2015 12:15:00 +0200
Greg Kurz gk...@linux.vnet.ibm.com wrote:

 Hi,
 
 This patchset allows vhost to be used with legacy virtio when guest and host
 have a different endianness.
 
 Patch 7 got rewritten according to Cornelia's and Michael's comments. I have
 also introduced patch 8 that brings BE vnet headers support to tun/macvtap.
 
 This series is enough to have vhost_net working flawlessly. I could
 succesfully reboot guests from ppc64 to ppc64le and vice-versa on ppc64
 and ppc64le hosts.
 

Michael,

I am ready to post v5 with the changes suggested by Cornelia... Do you have any
extra comments on this v4 ? 

--
Greg

 ---
 
 Greg Kurz (8):
   virtio: introduce virtio_is_little_endian() helper
   tun: add tun_is_little_endian() helper
   macvtap: introduce macvtap_is_little_endian() helper
   vringh: introduce vringh_is_little_endian() helper
   vhost: introduce vhost_is_little_endian() helper
   virtio: add explicit big-endian support to memory accessors
   vhost: feature to set the vring endianness
   macvtap/tun: add VNET_BE flag
 
 
  drivers/net/Kconfig  |   12 ++
  drivers/net/macvtap.c|   69 ++-
  drivers/net/tun.c|   71 +++-
  drivers/vhost/Kconfig|   10 +
  drivers/vhost/vhost.c|   76 
 ++
  drivers/vhost/vhost.h|   25 ++---
  include/linux/virtio_byteorder.h |   24 +++-
  include/linux/virtio_config.h|   19 +++---
  include/linux/vringh.h   |   19 +++---
  include/uapi/linux/if_tun.h  |2 +
  include/uapi/linux/vhost.h   |9 +
  11 files changed, 303 insertions(+), 33 deletions(-)
 
 --
 Greg
 
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 virtualizat...@lists.linux-foundation.org
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Re: [PATCH v4 7/8] vhost: feature to set the vring endianness

[Greg Kurz]

On Tue, 14 Apr 2015 16:20:23 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 On Fri, 10 Apr 2015 12:19:16 +0200
 Greg Kurz gk...@linux.vnet.ibm.com wrote:
 
  This patch brings cross-endian support to vhost when used to implement
  legacy virtio devices. Since it is a relatively rare situation, the
  feature availability is controlled by a kernel config option (not set
  by default).
  
  The vq-is_le boolean field is added to cache the endianness to be
  used for ring accesses. It defaults to native endian, as expected
  by legacy virtio devices. When the ring gets active, we force little
  endian if the device is modern. When the ring is deactivated, we
  revert to the native endian default.
  
  If cross-endian was compiled in, a vq-user_be boolean field is added
  so that userspace may request a specific endianness. This field is
  used to override the default when activating the ring of a legacy
  device. It has no effect on modern devices.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
   drivers/vhost/Kconfig  |   10 ++
   drivers/vhost/vhost.c  |   76 
  +++-
   drivers/vhost/vhost.h  |   12 +--
   include/uapi/linux/vhost.h |9 +
   4 files changed, 103 insertions(+), 4 deletions(-)
 
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +static long vhost_set_vring_big_endian(struct vhost_virtqueue *vq,
  +  int __user *argp)
  +{
  +   struct vhost_vring_state s;
  +
  +   if (vq-private_data)
  +   return -EBUSY;
  +
  +   if (copy_from_user(s, argp, sizeof(s)))
  +   return -EFAULT;
  +
  +   if (s.num  s.num != 1)
 
 Checking for s.num  1 might be more obvious at a glance?
 

Sure since s.num is unsigned.

  +   return -EINVAL;
  +
  +   vq-user_be = s.num;
  +
  +   return 0;
  +}
  +
 
 (...)
 
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +static void vhost_init_is_le(struct vhost_virtqueue *vq)
  +{
  +   vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
 
 So if the endianness is not explicitly set to BE, it will be forced to
 LE (instead of native endian)? Won't that break userspace that does not
 yet use the new interface when CONFIG_VHOST_SET_ENDIAN_LEGACY is set?
 

If userspace doesn't use the new interface, then vq-user_be will retain its
default value that was set in vhost_vq_reset(), i.e. :

 vq-user_be = !virtio_legacy_is_little_endian();

This means default is native endian.

What about adding this comment ?

static void vhost_init_is_le(struct vhost_virtqueue *vq)
{
/* Note for legacy virtio: user_be is initialized in vhost_vq_reset()
 * according to the host endianness. If userspace does not set an
 * explicit endianness, the default behavior is native endian, as
 * expected by legacy virtio.
 */
vq-is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq-user_be;
}

  +}
  +#else
  +static void vhost_init_is_le(struct vhost_virtqueue *vq)
  +{
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   vq-is_le = true;
  +}
  +#endif
  +
   int vhost_init_used(struct vhost_virtqueue *vq)
   {
  __virtio16 last_used_idx;
  int r;
  -   if (!vq-private_data)
  +   if (!vq-private_data) {
  +   vq-is_le = virtio_legacy_is_little_endian();
  return 0;
  +   }
  +
  +   vhost_init_is_le(vq);
  
  r = vhost_update_used_flags(vq);
  if (r)

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Re: [PATCH v3 7/7] vhost: feature to set the vring endianness

[Greg Kurz]

On Tue, 7 Apr 2015 17:52:28 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Tue, Apr 07, 2015 at 02:19:31PM +0200, Greg Kurz wrote:
  This patch brings cross-endian support to vhost when used to implement
  legacy virtio devices. Since it is a relatively rare situation, the
  feature availability is controlled by a kernel config option (not set
  by default).
  
  The ioctls introduced by this patch are for legacy only: virtio 1.0
  devices are returned EPERM.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
 
 EINVAL probably makes more sense?
 

I had choosen EPERM because the error isn't related to the arguments
being passed by userspace. It simply does not make sense to set the
vring endianness for a virtio 1.0 device.

That being said, I am perfectly fine with EINVAL. :)

  ---
   drivers/vhost/Kconfig  |   10 
   drivers/vhost/vhost.c  |   55 
  
   drivers/vhost/vhost.h  |   17 +-
   include/uapi/linux/vhost.h |5 
   4 files changed, 86 insertions(+), 1 deletion(-)
  
  Changes since v2:
  - fixed typos in Kconfig description
  - renamed vq-legacy_big_endian to vq-legacy_is_little_endian
  - vq-legacy_is_little_endian reset to default in vhost_vq_reset()
  - dropped VHOST_F_SET_ENDIAN_LEGACY feature
  - dropped struct vhost_vring_endian from the user API (re-use
struct vhost_vring_state instead)
  - added VHOST_GET_VRING_ENDIAN_LEGACY ioctl
  - introduced more helpers and stubs to avoid polluting the code with ifdefs
  
  
  diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
  index 017a1e8..0aec88c 100644
  --- a/drivers/vhost/Kconfig
  +++ b/drivers/vhost/Kconfig
  @@ -32,3 +32,13 @@ config VHOST
  ---help---
This option is selected by any driver which needs to access
the core of vhost.
  +
  +config VHOST_SET_ENDIAN_LEGACY
  +   bool Cross-endian support for host kernel accelerator
  +   default n
  +   ---help---
  + This option allows vhost to support guests with a different byte
  + ordering from host. It is disabled by default since it adds overhead
  + and it is only needed by a few platforms (powerpc and arm).
  +
  + If unsure, say N.
  diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
  index 2ee2826..3529a3c 100644
  --- a/drivers/vhost/vhost.c
  +++ b/drivers/vhost/vhost.c
  @@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
  vq-call = NULL;
  vq-log_ctx = NULL;
  vq-memory = NULL;
  +   vq-legacy_is_little_endian = virtio_legacy_is_little_endian();
   }
   
   static int vhost_worker(void *data)
  @@ -630,6 +631,54 @@ static long vhost_set_memory(struct vhost_dev *d, 
  struct vhost_memory __user *m)
  return 0;
   }
   
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
  + void __user *argp)
  +{
  +   struct vhost_vring_state s;
  +
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return -EPERM;
 
 EINVAL probably makes more sense? But I'm not sure this
 is helpful: one can set VIRTIO_F_VERSION_1 afterwards,
 and your patch does not seem to detect this.
 

Yeah, when I dropped the *bogus* feature from v2, I forgot to patch
VHOST_SET_FEATURES accordingly... But thinking about it now, the choice
to error out when setting VIRTIO_F_VERSION_1 because cross-endian legacy
was set before looks terrible... :-\

 
 
  +
  +   if (copy_from_user(s, argp, sizeof(s)))
  +   return -EFAULT;
  +
  +   vq-legacy_is_little_endian = !!s.num;
  +   return 0;
  +}
  +
  +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
  + u32 idx,
  + void __user *argp)
  +{
  +   struct vhost_vring_state s = {
  +   .index = idx,
  +   .num = vq-legacy_is_little_endian
  +   };
  +
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return -EPERM;
  +
  +   if (copy_to_user(argp, s, sizeof(s)))
  +   return -EFAULT;
  +
  +   return 0;
  +}
  +#else
  +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
  + void __user *argp)
  +{
  +   return 0;
  +}
  +
  +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
  + u32 idx,
  + void __user *argp)
  +{
  +   return 0;
  +}
 
 Should be -ENOIOCTLCMD?
 

Sure.

  +#endif /* CONFIG_VHOST_SET_ENDIAN_LEGACY */
  +
   long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
   {
  struct file *eventfp, *filep = NULL;
  @@ -806,6 +855,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, 
  void __user *argp)
  } else
  filep = eventfp;
  break;
  +   case VHOST_SET_VRING_ENDIAN_LEGACY:
  +   r

Re: [PATCH v3 7/7] vhost: feature to set the vring endianness

[Greg Kurz]

On Tue, 7 Apr 2015 17:01:31 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 On Tue, 07 Apr 2015 14:19:31 +0200
 Greg Kurz gk...@linux.vnet.ibm.com wrote:
 
  This patch brings cross-endian support to vhost when used to implement
  legacy virtio devices. Since it is a relatively rare situation, the
  feature availability is controlled by a kernel config option (not set
  by default).
  
  The ioctls introduced by this patch are for legacy only: virtio 1.0
  devices are returned EPERM.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
   drivers/vhost/Kconfig  |   10 
   drivers/vhost/vhost.c  |   55 
  
   drivers/vhost/vhost.h  |   17 +-
   include/uapi/linux/vhost.h |5 
   4 files changed, 86 insertions(+), 1 deletion(-)
 
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
  + void __user *argp)
  +{
  +   struct vhost_vring_state s;
  +
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return -EPERM;
  +
  +   if (copy_from_user(s, argp, sizeof(s)))
  +   return -EFAULT;
  +
  +   vq-legacy_is_little_endian = !!s.num;
  +   return 0;
  +}
  +
  +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
  + u32 idx,
  + void __user *argp)
  +{
  +   struct vhost_vring_state s = {
  +   .index = idx,
  +   .num = vq-legacy_is_little_endian
  +   };
  +
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return -EPERM;
  +
  +   if (copy_to_user(argp, s, sizeof(s)))
  +   return -EFAULT;
  +
  +   return 0;
  +}
  +#else
  +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
  + void __user *argp)
  +{
  +   return 0;
 
 I'm wondering whether this handler should return an error if the
 feature is not configured for the kernel? How can the userspace caller
 find out whether it has successfully prompted the kernel to handle the
 endianness correctly?
 

Yes you're right. I think -ENOIOCTLCMD as suggested by Michael is a good
candidate.

Thanks.

  +}
  +
  +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
  + u32 idx,
  + void __user *argp)
  +{
  +   return 0;
  +}
  +#endif /* CONFIG_VHOST_SET_ENDIAN_LEGACY */

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Re: [PATCH v3 7/7] vhost: feature to set the vring endianness

[Greg Kurz]

On Tue, 7 Apr 2015 18:11:29 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Tue, Apr 07, 2015 at 02:19:31PM +0200, Greg Kurz wrote:
  This patch brings cross-endian support to vhost when used to implement
  legacy virtio devices. Since it is a relatively rare situation, the
  feature availability is controlled by a kernel config option (not set
  by default).
  
  The ioctls introduced by this patch are for legacy only: virtio 1.0
  devices are returned EPERM.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
   drivers/vhost/Kconfig  |   10 
   drivers/vhost/vhost.c  |   55 
  
   drivers/vhost/vhost.h  |   17 +-
   include/uapi/linux/vhost.h |5 
   4 files changed, 86 insertions(+), 1 deletion(-)
  
  Changes since v2:
  - fixed typos in Kconfig description
  - renamed vq-legacy_big_endian to vq-legacy_is_little_endian
  - vq-legacy_is_little_endian reset to default in vhost_vq_reset()
  - dropped VHOST_F_SET_ENDIAN_LEGACY feature
  - dropped struct vhost_vring_endian from the user API (re-use
struct vhost_vring_state instead)
  - added VHOST_GET_VRING_ENDIAN_LEGACY ioctl
  - introduced more helpers and stubs to avoid polluting the code with ifdefs
  
  
  diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
  index 017a1e8..0aec88c 100644
  --- a/drivers/vhost/Kconfig
  +++ b/drivers/vhost/Kconfig
  @@ -32,3 +32,13 @@ config VHOST
  ---help---
This option is selected by any driver which needs to access
the core of vhost.
  +
  +config VHOST_SET_ENDIAN_LEGACY
  +   bool Cross-endian support for host kernel accelerator
  +   default n
  +   ---help---
  + This option allows vhost to support guests with a different byte
  + ordering from host. It is disabled by default since it adds overhead
  + and it is only needed by a few platforms (powerpc and arm).
  +
  + If unsure, say N.
  diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
  index 2ee2826..3529a3c 100644
  --- a/drivers/vhost/vhost.c
  +++ b/drivers/vhost/vhost.c
  @@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
  vq-call = NULL;
  vq-log_ctx = NULL;
  vq-memory = NULL;
  +   vq-legacy_is_little_endian = virtio_legacy_is_little_endian();
   }
   
   static int vhost_worker(void *data)
  @@ -630,6 +631,54 @@ static long vhost_set_memory(struct vhost_dev *d, 
  struct vhost_memory __user *m)
  return 0;
   }
   
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
  + void __user *argp)
  +{
  +   struct vhost_vring_state s;
  +
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return -EPERM;
  +
  +   if (copy_from_user(s, argp, sizeof(s)))
  +   return -EFAULT;
  +
  +   vq-legacy_is_little_endian = !!s.num;
  +   return 0;
  +}
  +
  +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
  + u32 idx,
  + void __user *argp)
  +{
  +   struct vhost_vring_state s = {
  +   .index = idx,
  +   .num = vq-legacy_is_little_endian
  +   };
  +
  +   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
  +   return -EPERM;
  +
  +   if (copy_to_user(argp, s, sizeof(s)))
  +   return -EFAULT;
  +
  +   return 0;
  +}
  +#else
  +static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
  + void __user *argp)
  +{
  +   return 0;
  +}
  +
  +static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
  + u32 idx,
  + void __user *argp)
  +{
  +   return 0;
  +}
  +#endif /* CONFIG_VHOST_SET_ENDIAN_LEGACY */
  +
   long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
   {
  struct file *eventfp, *filep = NULL;
  @@ -806,6 +855,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, 
  void __user *argp)
  } else
  filep = eventfp;
  break;
  +   case VHOST_SET_VRING_ENDIAN_LEGACY:
  +   r = vhost_set_vring_endian_legacy(vq, argp);
  +   break;
  +   case VHOST_GET_VRING_ENDIAN_LEGACY:
  +   r = vhost_get_vring_endian_legacy(vq, idx, argp);
  +   break;
  default:
  r = -ENOIOCTLCMD;
  }
  diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
  index 4e9a186..981ba06 100644
  --- a/drivers/vhost/vhost.h
  +++ b/drivers/vhost/vhost.h
  @@ -106,6 +106,9 @@ struct vhost_virtqueue {
  /* Log write descriptors */
  void __user *log_base;
  struct vhost_log *log;
  +
  +   /* We need to know the device endianness with legacy virtio. */
  +   bool legacy_is_little_endian;
   };
   
   struct vhost_dev {
  @@ -173,11 +176,23 @@ static inline bool vhost_has_feature(struct

[PATCH v3 0/7] vhost: support for cross endian guests

[Greg Kurz]

Hi,

This patchset allows vhost to be used with legacy virtio when guest and host
have a different endianness.

Patches 1-6 remain the same as the previous post. Patch 7 was heavily changed
according to MST's comments.

---

Greg Kurz (7):
  virtio: introduce virtio_is_little_endian() helper
  tun: add tun_is_little_endian() helper
  macvtap: introduce macvtap_is_little_endian() helper
  vringh: introduce vringh_is_little_endian() helper
  vhost: introduce vhost_is_little_endian() helper
  virtio: add explicit big-endian support to memory accessors
  vhost: feature to set the vring endianness


 drivers/net/macvtap.c|   11 ++--
 drivers/net/tun.c|   11 ++--
 drivers/vhost/Kconfig|   10 +++
 drivers/vhost/vhost.c|   55 ++
 drivers/vhost/vhost.h|   34 +++
 include/linux/virtio_byteorder.h |   24 ++---
 include/linux/virtio_config.h|   19 +
 include/linux/vringh.h   |   19 +
 include/uapi/linux/vhost.h   |5 +++
 9 files changed, 156 insertions(+), 32 deletions(-)

--
Greg

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[PATCH v3 3/7] macvtap: introduce macvtap_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/macvtap.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 27ecc5c..a2f2958 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -49,14 +49,19 @@ struct macvtap_queue {
 
 #define MACVTAP_VNET_LE 0x8000
 
+static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
+{
+   return q-flags  MACVTAP_VNET_LE;
+}
+
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
 {
-   return __virtio16_to_cpu(q-flags  MACVTAP_VNET_LE, val);
+   return __virtio16_to_cpu(macvtap_is_little_endian(q), val);
 }
 
 static inline __virtio16 cpu_to_macvtap16(struct macvtap_queue *q, u16 val)
 {
-   return __cpu_to_virtio16(q-flags  MACVTAP_VNET_LE, val);
+   return __cpu_to_virtio16(macvtap_is_little_endian(q), val);
 }
 
 static struct proto macvtap_proto = {

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[PATCH v3 2/7] tun: add tun_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/tun.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 857dca4..3c3d6c0 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -206,14 +206,19 @@ struct tun_struct {
u32 flow_count;
 };
 
+static inline bool tun_is_little_endian(struct tun_struct *tun)
+{
+   return tun-flags  TUN_VNET_LE;
+}
+
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
 {
-   return __virtio16_to_cpu(tun-flags  TUN_VNET_LE, val);
+   return __virtio16_to_cpu(tun_is_little_endian(tun), val);
 }
 
 static inline __virtio16 cpu_to_tun16(struct tun_struct *tun, u16 val)
 {
-   return __cpu_to_virtio16(tun-flags  TUN_VNET_LE, val);
+   return __cpu_to_virtio16(tun_is_little_endian(tun), val);
 }
 
 static inline u32 tun_hashfn(u32 rxhash)

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[PATCH v3 1/7] virtio: introduce virtio_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/virtio_config.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index ca3ed78..bd1a582 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -205,35 +205,40 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)
return 0;
 }
 
+static inline bool virtio_is_little_endian(struct virtio_device *vdev)
+{
+   return virtio_has_feature(vdev, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
 {
-   return __virtio16_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
 {
-   return __cpu_to_virtio16(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(virtio_is_little_endian(vdev), val);
 }
 
 static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
 {
-   return __virtio32_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
 {
-   return __cpu_to_virtio32(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(virtio_is_little_endian(vdev), val);
 }
 
 static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
 {
-   return __virtio64_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 {
-   return __cpu_to_virtio64(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
 }
 
 /* Config space accessors. */

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[PATCH v3 6/7] virtio: add explicit big-endian support to memory accessors

[Greg Kurz]

The current memory accessors logic is:
- little endian if little_endian
- native endian (i.e. no byteswap) if !little_endian

If we want to fully support cross-endian vhost, we also need to be
able to convert to big endian.

Instead of changing the little_endian argument to some 3-value enum, this
patch changes the logic to:
- little endian if little_endian
- big endian if !little_endian

The native endian case is handled by all users with a trivial helper. This
patch doesn't change any functionality, nor it does add overhead.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/macvtap.c|4 +++-
 drivers/net/tun.c|4 +++-
 drivers/vhost/vhost.h|4 +++-
 include/linux/virtio_byteorder.h |   24 ++--
 include/linux/virtio_config.h|4 +++-
 include/linux/vringh.h   |4 +++-
 6 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index a2f2958..0a03a66 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -51,7 +51,9 @@ struct macvtap_queue {
 
 static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
 {
-   return q-flags  MACVTAP_VNET_LE;
+   if (q-flags  MACVTAP_VNET_LE)
+   return true;
+   return virtio_legacy_is_little_endian();
 }
 
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 3c3d6c0..053f9b6 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -208,7 +208,9 @@ struct tun_struct {
 
 static inline bool tun_is_little_endian(struct tun_struct *tun)
 {
-   return tun-flags  TUN_VNET_LE;
+   if (tun-flags  TUN_VNET_LE)
+   return true;
+   return virtio_legacy_is_little_endian();
 }
 
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 6a49960..4e9a186 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -175,7 +175,9 @@ static inline bool vhost_has_feature(struct vhost_virtqueue 
*vq, int bit)
 
 static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
 {
-   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+   return true;
+   return virtio_legacy_is_little_endian();
 }
 
 /* Memory accessors */
diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
index 51865d0..ce63a2c 100644
--- a/include/linux/virtio_byteorder.h
+++ b/include/linux/virtio_byteorder.h
@@ -3,17 +3,21 @@
 #include linux/types.h
 #include uapi/linux/virtio_types.h
 
-/*
- * Low-level memory accessors for handling virtio in modern little endian and 
in
- * compatibility native endian format.
- */
+static inline bool virtio_legacy_is_little_endian(void)
+{
+#ifdef __LITTLE_ENDIAN
+   return true;
+#else
+   return false;
+#endif
+}
 
 static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
 {
if (little_endian)
return le16_to_cpu((__force __le16)val);
else
-   return (__force u16)val;
+   return be16_to_cpu((__force __be16)val);
 }
 
 static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
@@ -21,7 +25,7 @@ static inline __virtio16 __cpu_to_virtio16(bool 
little_endian, u16 val)
if (little_endian)
return (__force __virtio16)cpu_to_le16(val);
else
-   return (__force __virtio16)val;
+   return (__force __virtio16)cpu_to_be16(val);
 }
 
 static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
@@ -29,7 +33,7 @@ static inline u32 __virtio32_to_cpu(bool little_endian, 
__virtio32 val)
if (little_endian)
return le32_to_cpu((__force __le32)val);
else
-   return (__force u32)val;
+   return be32_to_cpu((__force __be32)val);
 }
 
 static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
@@ -37,7 +41,7 @@ static inline __virtio32 __cpu_to_virtio32(bool 
little_endian, u32 val)
if (little_endian)
return (__force __virtio32)cpu_to_le32(val);
else
-   return (__force __virtio32)val;
+   return (__force __virtio32)cpu_to_be32(val);
 }
 
 static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)
@@ -45,7 +49,7 @@ static inline u64 __virtio64_to_cpu(bool little_endian, 
__virtio64 val)
if (little_endian)
return le64_to_cpu((__force __le64)val);
else
-   return (__force u64)val;
+   return be64_to_cpu((__force __be64)val);
 }
 
 static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val)
@@ -53,7 +57,7 @@ static inline __virtio64 __cpu_to_virtio64(bool 
little_endian, u64 val)
if (little_endian)
return (__force __virtio64)cpu_to_le64

[PATCH v3 5/7] vhost: introduce vhost_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/vhost.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8c1c792..6a49960 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -173,34 +173,39 @@ static inline bool vhost_has_feature(struct 
vhost_virtqueue *vq, int bit)
return vq-acked_features  (1ULL  bit);
 }
 
+static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
+{
+   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
 {
-   return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio16 cpu_to_vhost16(struct vhost_virtqueue *vq, u16 val)
 {
-   return __cpu_to_virtio16(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(vhost_is_little_endian(vq), val);
 }
 
 static inline u32 vhost32_to_cpu(struct vhost_virtqueue *vq, __virtio32 val)
 {
-   return __virtio32_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio32 cpu_to_vhost32(struct vhost_virtqueue *vq, u32 val)
 {
-   return __cpu_to_virtio32(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(vhost_is_little_endian(vq), val);
 }
 
 static inline u64 vhost64_to_cpu(struct vhost_virtqueue *vq, __virtio64 val)
 {
-   return __virtio64_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio64 cpu_to_vhost64(struct vhost_virtqueue *vq, u64 val)
 {
-   return __cpu_to_virtio64(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(vhost_is_little_endian(vq), val);
 }
 #endif

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[PATCH v3 7/7] vhost: feature to set the vring endianness

[Greg Kurz]

This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the
feature availability is controlled by a kernel config option (not set
by default).

The ioctls introduced by this patch are for legacy only: virtio 1.0
devices are returned EPERM.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/Kconfig  |   10 
 drivers/vhost/vhost.c  |   55 
 drivers/vhost/vhost.h  |   17 +-
 include/uapi/linux/vhost.h |5 
 4 files changed, 86 insertions(+), 1 deletion(-)

Changes since v2:
- fixed typos in Kconfig description
- renamed vq-legacy_big_endian to vq-legacy_is_little_endian
- vq-legacy_is_little_endian reset to default in vhost_vq_reset()
- dropped VHOST_F_SET_ENDIAN_LEGACY feature
- dropped struct vhost_vring_endian from the user API (re-use
  struct vhost_vring_state instead)
- added VHOST_GET_VRING_ENDIAN_LEGACY ioctl
- introduced more helpers and stubs to avoid polluting the code with ifdefs


diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 017a1e8..0aec88c 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -32,3 +32,13 @@ config VHOST
---help---
  This option is selected by any driver which needs to access
  the core of vhost.
+
+config VHOST_SET_ENDIAN_LEGACY
+   bool Cross-endian support for host kernel accelerator
+   default n
+   ---help---
+ This option allows vhost to support guests with a different byte
+ ordering from host. It is disabled by default since it adds overhead
+ and it is only needed by a few platforms (powerpc and arm).
+
+ If unsure, say N.
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..3529a3c 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq-call = NULL;
vq-log_ctx = NULL;
vq-memory = NULL;
+   vq-legacy_is_little_endian = virtio_legacy_is_little_endian();
 }
 
 static int vhost_worker(void *data)
@@ -630,6 +631,54 @@ static long vhost_set_memory(struct vhost_dev *d, struct 
vhost_memory __user *m)
return 0;
 }
 
+#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
+static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
+ void __user *argp)
+{
+   struct vhost_vring_state s;
+
+   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+   return -EPERM;
+
+   if (copy_from_user(s, argp, sizeof(s)))
+   return -EFAULT;
+
+   vq-legacy_is_little_endian = !!s.num;
+   return 0;
+}
+
+static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
+ u32 idx,
+ void __user *argp)
+{
+   struct vhost_vring_state s = {
+   .index = idx,
+   .num = vq-legacy_is_little_endian
+   };
+
+   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+   return -EPERM;
+
+   if (copy_to_user(argp, s, sizeof(s)))
+   return -EFAULT;
+
+   return 0;
+}
+#else
+static long vhost_set_vring_endian_legacy(struct vhost_virtqueue *vq,
+ void __user *argp)
+{
+   return 0;
+}
+
+static long vhost_get_vring_endian_legacy(struct vhost_virtqueue *vq,
+ u32 idx,
+ void __user *argp)
+{
+   return 0;
+}
+#endif /* CONFIG_VHOST_SET_ENDIAN_LEGACY */
+
 long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
 {
struct file *eventfp, *filep = NULL;
@@ -806,6 +855,12 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, 
void __user *argp)
} else
filep = eventfp;
break;
+   case VHOST_SET_VRING_ENDIAN_LEGACY:
+   r = vhost_set_vring_endian_legacy(vq, argp);
+   break;
+   case VHOST_GET_VRING_ENDIAN_LEGACY:
+   r = vhost_get_vring_endian_legacy(vq, idx, argp);
+   break;
default:
r = -ENOIOCTLCMD;
}
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 4e9a186..981ba06 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -106,6 +106,9 @@ struct vhost_virtqueue {
/* Log write descriptors */
void __user *log_base;
struct vhost_log *log;
+
+   /* We need to know the device endianness with legacy virtio. */
+   bool legacy_is_little_endian;
 };
 
 struct vhost_dev {
@@ -173,11 +176,23 @@ static inline bool vhost_has_feature(struct 
vhost_virtqueue *vq, int bit)
return vq-acked_features  (1ULL  bit);
 }
 
+#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
+static inline bool vhost_legacy_is_little_endian(struct vhost_virtqueue *vq

[PATCH v3 4/7] vringh: introduce vringh_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/vringh.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index a3fa537..3ed62ef 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -226,33 +226,38 @@ static inline void vringh_notify(struct vringh *vrh)
vrh-notify(vrh);
 }
 
+static inline bool vringh_is_little_endian(const struct vringh *vrh)
+{
+   return vrh-little_endian;
+}
+
 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
 {
-   return __virtio16_to_cpu(vrh-little_endian, val);
+   return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
 {
-   return __cpu_to_virtio16(vrh-little_endian, val);
+   return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
 }
 
 static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
 {
-   return __virtio32_to_cpu(vrh-little_endian, val);
+   return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
 {
-   return __cpu_to_virtio32(vrh-little_endian, val);
+   return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
 }
 
 static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
 {
-   return __virtio64_to_cpu(vrh-little_endian, val);
+   return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
 {
-   return __cpu_to_virtio64(vrh-little_endian, val);
+   return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
 }
 #endif /* _LINUX_VRINGH_H */

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Re: [PATCH v3 0/7] vhost: support for cross endian guests

[Greg Kurz]

On Tue, 7 Apr 2015 17:55:08 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Tue, Apr 07, 2015 at 02:09:29PM +0200, Greg Kurz wrote:
  Hi,
  
  This patchset allows vhost to be used with legacy virtio when guest and host
  have a different endianness.
  
  Patches 1-6 remain the same as the previous post. Patch 7 was heavily 
  changed
  according to MST's comments.
 
 This still doesn't actually work, right?
 tun and macvtap need new ioctls too ...
 

Yes they do. I already have a patch but I wasn't sure if I should send it
along this series... Since it looks like there will be a v4, I'll add the
tun/macvtap patch.

Thanks.

--
Greg

  ---
  
  Greg Kurz (7):
virtio: introduce virtio_is_little_endian() helper
tun: add tun_is_little_endian() helper
macvtap: introduce macvtap_is_little_endian() helper
vringh: introduce vringh_is_little_endian() helper
vhost: introduce vhost_is_little_endian() helper
virtio: add explicit big-endian support to memory accessors
vhost: feature to set the vring endianness
  
  
   drivers/net/macvtap.c|   11 ++--
   drivers/net/tun.c|   11 ++--
   drivers/vhost/Kconfig|   10 +++
   drivers/vhost/vhost.c|   55 
  ++
   drivers/vhost/vhost.h|   34 +++
   include/linux/virtio_byteorder.h |   24 ++---
   include/linux/virtio_config.h|   19 +
   include/linux/vringh.h   |   19 +
   include/uapi/linux/vhost.h   |5 +++
   9 files changed, 156 insertions(+), 32 deletions(-)
  
  --
  Greg
 

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[PATCH v2 3/7] macvtap: introduce macvtap_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/macvtap.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 27ecc5c..a2f2958 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -49,14 +49,19 @@ struct macvtap_queue {
 
 #define MACVTAP_VNET_LE 0x8000
 
+static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
+{
+   return q-flags  MACVTAP_VNET_LE;
+}
+
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
 {
-   return __virtio16_to_cpu(q-flags  MACVTAP_VNET_LE, val);
+   return __virtio16_to_cpu(macvtap_is_little_endian(q), val);
 }
 
 static inline __virtio16 cpu_to_macvtap16(struct macvtap_queue *q, u16 val)
 {
-   return __cpu_to_virtio16(q-flags  MACVTAP_VNET_LE, val);
+   return __cpu_to_virtio16(macvtap_is_little_endian(q), val);
 }
 
 static struct proto macvtap_proto = {

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[PATCH v2 4/7] vringh: introduce vringh_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/vringh.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index a3fa537..3ed62ef 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -226,33 +226,38 @@ static inline void vringh_notify(struct vringh *vrh)
vrh-notify(vrh);
 }
 
+static inline bool vringh_is_little_endian(const struct vringh *vrh)
+{
+   return vrh-little_endian;
+}
+
 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
 {
-   return __virtio16_to_cpu(vrh-little_endian, val);
+   return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
 {
-   return __cpu_to_virtio16(vrh-little_endian, val);
+   return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
 }
 
 static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
 {
-   return __virtio32_to_cpu(vrh-little_endian, val);
+   return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
 {
-   return __cpu_to_virtio32(vrh-little_endian, val);
+   return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
 }
 
 static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
 {
-   return __virtio64_to_cpu(vrh-little_endian, val);
+   return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
 }
 
 static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
 {
-   return __cpu_to_virtio64(vrh-little_endian, val);
+   return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
 }
 #endif /* _LINUX_VRINGH_H */

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[PATCH v2 1/7] virtio: introduce virtio_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 include/linux/virtio_config.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index ca3ed78..bd1a582 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -205,35 +205,40 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)
return 0;
 }
 
+static inline bool virtio_is_little_endian(struct virtio_device *vdev)
+{
+   return virtio_has_feature(vdev, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
 {
-   return __virtio16_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
 {
-   return __cpu_to_virtio16(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(virtio_is_little_endian(vdev), val);
 }
 
 static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
 {
-   return __virtio32_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
 {
-   return __cpu_to_virtio32(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(virtio_is_little_endian(vdev), val);
 }
 
 static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
 {
-   return __virtio64_to_cpu(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(virtio_is_little_endian(vdev), val);
 }
 
 static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 {
-   return __cpu_to_virtio64(virtio_has_feature(vdev, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
 }
 
 /* Config space accessors. */

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[PATCH v2 5/7] vhost: introduce vhost_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/vhost.h |   17 +++--
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8c1c792..6a49960 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -173,34 +173,39 @@ static inline bool vhost_has_feature(struct 
vhost_virtqueue *vq, int bit)
return vq-acked_features  (1ULL  bit);
 }
 
+static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
+{
+   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+}
+
 /* Memory accessors */
 static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
 {
-   return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio16 cpu_to_vhost16(struct vhost_virtqueue *vq, u16 val)
 {
-   return __cpu_to_virtio16(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(vhost_is_little_endian(vq), val);
 }
 
 static inline u32 vhost32_to_cpu(struct vhost_virtqueue *vq, __virtio32 val)
 {
-   return __virtio32_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio32 cpu_to_vhost32(struct vhost_virtqueue *vq, u32 val)
 {
-   return __cpu_to_virtio32(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(vhost_is_little_endian(vq), val);
 }
 
 static inline u64 vhost64_to_cpu(struct vhost_virtqueue *vq, __virtio64 val)
 {
-   return __virtio64_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio64 cpu_to_vhost64(struct vhost_virtqueue *vq, u64 val)
 {
-   return __cpu_to_virtio64(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(vhost_is_little_endian(vq), val);
 }
 #endif

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[PATCH v2 2/7] tun: add tun_is_little_endian() helper

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/tun.c |9 +++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 857dca4..3c3d6c0 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -206,14 +206,19 @@ struct tun_struct {
u32 flow_count;
 };
 
+static inline bool tun_is_little_endian(struct tun_struct *tun)
+{
+   return tun-flags  TUN_VNET_LE;
+}
+
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
 {
-   return __virtio16_to_cpu(tun-flags  TUN_VNET_LE, val);
+   return __virtio16_to_cpu(tun_is_little_endian(tun), val);
 }
 
 static inline __virtio16 cpu_to_tun16(struct tun_struct *tun, u16 val)
 {
-   return __cpu_to_virtio16(tun-flags  TUN_VNET_LE, val);
+   return __cpu_to_virtio16(tun_is_little_endian(tun), val);
 }
 
 static inline u32 tun_hashfn(u32 rxhash)

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[PATCH v2 0/7] vhost: support for cross endian guests

[Greg Kurz]

Hi,

This patchset allows vhost to be used with legacy virtio when guest and host
have a different endianness. It is a complete rework of my initial post.

Patches 1 to 5 are preliminary work: we move the endianness check out of all
memory accessors to separate functions.

Patch 6 changes the semantics of the accessors so that they have explicit big
endian support.

Patch 7 brings the cross-endian feature, with the following changes since v1:
- conditionnal enablement through a kernel config
- introduction of a new vhost feature to advertise cross-endian to userspace

The tentative to fix vnet headers was dropped for the moment. As a consequnce,
vhost_net still fails to work with cross-endian. It will be fixed in another
patchset I'm currently working on.

---

Greg Kurz (7):
  virtio: introduce virtio_is_little_endian() helper
  tun: add tun_is_little_endian() helper
  macvtap: introduce macvtap_is_little_endian() helper
  vringh: introduce vringh_is_little_endian() helper
  vhost: introduce vhost_is_little_endian() helper
  virtio: add explicit big-endian support to memory accessors
  vhost: feature to set the vring endianness


 drivers/net/macvtap.c|   11 +--
 drivers/net/tun.c|   11 +--
 drivers/vhost/Kconfig|   10 ++
 drivers/vhost/net.c  |5 +
 drivers/vhost/scsi.c |4 
 drivers/vhost/test.c |4 
 drivers/vhost/vhost.c|   19 +++
 drivers/vhost/vhost.h|   32 +---
 include/linux/virtio_byteorder.h |   24 ++--
 include/linux/virtio_config.h|   19 +--
 include/linux/vringh.h   |   19 +--
 include/uapi/linux/vhost.h   |   10 ++
 12 files changed, 135 insertions(+), 33 deletions(-)

--
Greg

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[PATCH v2 6/7] virtio: add explicit big-endian support to memory accessors

[Greg Kurz]

The current memory accessors logic is:
- little endian if little_endian
- native endian (i.e. no byteswap) if !little_endian

If we want to fully support cross-endian vhost, we also need to be
able to convert to big endian.

Instead of changing the little_endian argument to some 3-value enum, this
patch changes the logic to:
- little endian if little_endian
- big endian if !little_endian

The native endian case is handled by all users with a trivial helper. This
patch doesn't change any functionality, nor it does add overhead.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/net/macvtap.c|4 +++-
 drivers/net/tun.c|4 +++-
 drivers/vhost/vhost.h|4 +++-
 include/linux/virtio_byteorder.h |   24 ++--
 include/linux/virtio_config.h|4 +++-
 include/linux/vringh.h   |4 +++-
 6 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index a2f2958..0a03a66 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -51,7 +51,9 @@ struct macvtap_queue {
 
 static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
 {
-   return q-flags  MACVTAP_VNET_LE;
+   if (q-flags  MACVTAP_VNET_LE)
+   return true;
+   return virtio_legacy_is_little_endian();
 }
 
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 3c3d6c0..053f9b6 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -208,7 +208,9 @@ struct tun_struct {
 
 static inline bool tun_is_little_endian(struct tun_struct *tun)
 {
-   return tun-flags  TUN_VNET_LE;
+   if (tun-flags  TUN_VNET_LE)
+   return true;
+   return virtio_legacy_is_little_endian();
 }
 
 static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 6a49960..4e9a186 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -175,7 +175,9 @@ static inline bool vhost_has_feature(struct vhost_virtqueue 
*vq, int bit)
 
 static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
 {
-   return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
+   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+   return true;
+   return virtio_legacy_is_little_endian();
 }
 
 /* Memory accessors */
diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
index 51865d0..ce63a2c 100644
--- a/include/linux/virtio_byteorder.h
+++ b/include/linux/virtio_byteorder.h
@@ -3,17 +3,21 @@
 #include linux/types.h
 #include uapi/linux/virtio_types.h
 
-/*
- * Low-level memory accessors for handling virtio in modern little endian and 
in
- * compatibility native endian format.
- */
+static inline bool virtio_legacy_is_little_endian(void)
+{
+#ifdef __LITTLE_ENDIAN
+   return true;
+#else
+   return false;
+#endif
+}
 
 static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
 {
if (little_endian)
return le16_to_cpu((__force __le16)val);
else
-   return (__force u16)val;
+   return be16_to_cpu((__force __be16)val);
 }
 
 static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
@@ -21,7 +25,7 @@ static inline __virtio16 __cpu_to_virtio16(bool 
little_endian, u16 val)
if (little_endian)
return (__force __virtio16)cpu_to_le16(val);
else
-   return (__force __virtio16)val;
+   return (__force __virtio16)cpu_to_be16(val);
 }
 
 static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
@@ -29,7 +33,7 @@ static inline u32 __virtio32_to_cpu(bool little_endian, 
__virtio32 val)
if (little_endian)
return le32_to_cpu((__force __le32)val);
else
-   return (__force u32)val;
+   return be32_to_cpu((__force __be32)val);
 }
 
 static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
@@ -37,7 +41,7 @@ static inline __virtio32 __cpu_to_virtio32(bool 
little_endian, u32 val)
if (little_endian)
return (__force __virtio32)cpu_to_le32(val);
else
-   return (__force __virtio32)val;
+   return (__force __virtio32)cpu_to_be32(val);
 }
 
 static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)
@@ -45,7 +49,7 @@ static inline u64 __virtio64_to_cpu(bool little_endian, 
__virtio64 val)
if (little_endian)
return le64_to_cpu((__force __le64)val);
else
-   return (__force u64)val;
+   return be64_to_cpu((__force __be64)val);
 }
 
 static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val)
@@ -53,7 +57,7 @@ static inline __virtio64 __cpu_to_virtio64(bool 
little_endian, u64 val)
if (little_endian)
return (__force __virtio64)cpu_to_le64

[PATCH v2 7/7] vhost: feature to set the vring endianness

[Greg Kurz]

This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the feature
availability is controlled by a kernel config option (not set by default).

If cross-endian support is compiled in, vhost abvertises a new feature
to be negotiated with userspace. If userspace acknowledges the feature,
it can inform vhost about the endianness to use with a new ioctl.

This feature is mutually exclusive with virtio 1.0. Even if the vhost device
advertises virtio 1.0 and legacy cross-endian features, it cannot receive
aknowledgement for both at the same time.

Hot paths are being preserved from any penalty when the config option is
disabled or when virtio 1.0 is being used.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/Kconfig  |   10 ++
 drivers/vhost/net.c|5 +
 drivers/vhost/scsi.c   |4 
 drivers/vhost/test.c   |4 
 drivers/vhost/vhost.c  |   19 +++
 drivers/vhost/vhost.h  |   13 -
 include/uapi/linux/vhost.h |   10 ++
 7 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 017a1e8..5bb8da9 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -32,3 +32,13 @@ config VHOST
---help---
  This option is selected by any driver which needs to access
  the core of vhost.
+
+config VHOST_SET_ENDIAN_LEGACY
+   bool Cross-endian support for host kernel accelerator
+   default n
+   ---help---
+ This option allows vhost to support guests with a different byte
+ ordering. It is disabled by default since it adds overhead and it
+ is only needed by a few platforms (powerpc and arm).
+
+ If unsure, say n.
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2bbfc25..5274a44 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1011,6 +1011,11 @@ static int vhost_net_set_features(struct vhost_net *n, 
u64 features)
vhost_hlen = 0;
sock_hlen = hdr_len;
}
+
+   if (features  ((1ULL  VHOST_F_SET_ENDIAN_LEGACY) |
+   (1ULL  VIRTIO_F_VERSION_1)))
+   return -EINVAL;
+
mutex_lock(n-dev.mutex);
if ((features  (1  VHOST_F_LOG_ALL)) 
!vhost_log_access_ok(n-dev)) {
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 71df240..b53e9c2 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1544,6 +1544,10 @@ static int vhost_scsi_set_features(struct vhost_scsi 
*vs, u64 features)
if (features  ~VHOST_SCSI_FEATURES)
return -EOPNOTSUPP;
 
+   if (features  ((1ULL  VHOST_F_SET_ENDIAN_LEGACY) |
+   (1ULL  VIRTIO_F_VERSION_1)))
+   return -EINVAL;
+
mutex_lock(vs-dev.mutex);
if ((features  (1  VHOST_F_LOG_ALL)) 
!vhost_log_access_ok(vs-dev)) {
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index d9c501e..cfefdad 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -243,6 +243,10 @@ static int vhost_test_set_features(struct vhost_test *n, 
u64 features)
 {
struct vhost_virtqueue *vq;
 
+   if (features  ((1ULL  VHOST_F_SET_ENDIAN_LEGACY) |
+   (1ULL  VIRTIO_F_VERSION_1)))
+   return -EINVAL;
+
mutex_lock(n-dev.mutex);
if ((features  (1  VHOST_F_LOG_ALL)) 
!vhost_log_access_ok(n-dev)) {
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..60a0f32 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq-call = NULL;
vq-log_ctx = NULL;
vq-memory = NULL;
+   vq-legacy_big_endian = false;
 }
 
 static int vhost_worker(void *data)
@@ -806,6 +807,24 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, 
void __user *argp)
} else
filep = eventfp;
break;
+#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
+   case VHOST_SET_VRING_ENDIAN_LEGACY:
+   {
+   struct vhost_vring_endian e;
+
+   if (!vhost_has_feature(vq, VHOST_F_SET_ENDIAN_LEGACY)) {
+   r = -EINVAL;
+   break;
+   }
+
+   if (copy_from_user(e, argp, sizeof(e))) {
+   r = -EFAULT;
+   break;
+   }
+   vq-legacy_big_endian = e.is_big_endian;
+   break;
+   }
+#endif
default:
r = -ENOIOCTLCMD;
}
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 4e9a186..d50881d 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -106,6 +106,9 @@ struct vhost_virtqueue {
/* Log write descriptors */
void __user *log_base;
struct vhost_log *log

Re: [PATCH v2 7/7] vhost: feature to set the vring endianness

[Greg Kurz]

On Thu, 2 Apr 2015 16:20:46 +0200
Michael S. Tsirkin m...@redhat.com wrote:

 On Thu, Apr 02, 2015 at 03:17:13PM +0200, Greg Kurz wrote:
  This patch brings cross-endian support to vhost when used to implement
  legacy virtio devices. Since it is a relatively rare situation, the feature
  availability is controlled by a kernel config option (not set by default).
  
  If cross-endian support is compiled in, vhost abvertises a new feature
  to be negotiated with userspace. If userspace acknowledges the feature,
  it can inform vhost about the endianness to use with a new ioctl.
  
  This feature is mutually exclusive with virtio 1.0. Even if the vhost device
  advertises virtio 1.0 and legacy cross-endian features, it cannot receive
  aknowledgement for both at the same time.
  
  Hot paths are being preserved from any penalty when the config option is
  disabled or when virtio 1.0 is being used.
  
  Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
  ---
   drivers/vhost/Kconfig  |   10 ++
   drivers/vhost/net.c|5 +
   drivers/vhost/scsi.c   |4 
   drivers/vhost/test.c   |4 
   drivers/vhost/vhost.c  |   19 +++
   drivers/vhost/vhost.h  |   13 -
   include/uapi/linux/vhost.h |   10 ++
   7 files changed, 64 insertions(+), 1 deletion(-)
  
  diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
  index 017a1e8..5bb8da9 100644
  --- a/drivers/vhost/Kconfig
  +++ b/drivers/vhost/Kconfig
  @@ -32,3 +32,13 @@ config VHOST
  ---help---
This option is selected by any driver which needs to access
the core of vhost.
  +
  +config VHOST_SET_ENDIAN_LEGACY
  +   bool Cross-endian support for host kernel accelerator
  +   default n
  +   ---help---
  + This option allows vhost to support guests with a different byte
  + ordering
 
 from host
 
 . It is disabled by default since it adds overhead and it
  + is only needed by a few platforms (powerpc and arm).
  +
  + If unsure, say n.
 
 N
 
  diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
  index 2bbfc25..5274a44 100644
  --- a/drivers/vhost/net.c
  +++ b/drivers/vhost/net.c
  @@ -1011,6 +1011,11 @@ static int vhost_net_set_features(struct vhost_net 
  *n, u64 features)
  vhost_hlen = 0;
  sock_hlen = hdr_len;
  }
  +
  +   if (features  ((1ULL  VHOST_F_SET_ENDIAN_LEGACY) |
  +   (1ULL  VIRTIO_F_VERSION_1)))
  +   return -EINVAL;
  +
  mutex_lock(n-dev.mutex);
  if ((features  (1  VHOST_F_LOG_ALL)) 
  !vhost_log_access_ok(n-dev)) {
  diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
  index 71df240..b53e9c2 100644
  --- a/drivers/vhost/scsi.c
  +++ b/drivers/vhost/scsi.c
  @@ -1544,6 +1544,10 @@ static int vhost_scsi_set_features(struct vhost_scsi 
  *vs, u64 features)
  if (features  ~VHOST_SCSI_FEATURES)
  return -EOPNOTSUPP;
   
  +   if (features  ((1ULL  VHOST_F_SET_ENDIAN_LEGACY) |
  +   (1ULL  VIRTIO_F_VERSION_1)))
  +   return -EINVAL;
  +
  mutex_lock(vs-dev.mutex);
  if ((features  (1  VHOST_F_LOG_ALL)) 
  !vhost_log_access_ok(vs-dev)) {
  diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
  index d9c501e..cfefdad 100644
  --- a/drivers/vhost/test.c
  +++ b/drivers/vhost/test.c
  @@ -243,6 +243,10 @@ static int vhost_test_set_features(struct vhost_test 
  *n, u64 features)
   {
  struct vhost_virtqueue *vq;
   
  +   if (features  ((1ULL  VHOST_F_SET_ENDIAN_LEGACY) |
  +   (1ULL  VIRTIO_F_VERSION_1)))
  +   return -EINVAL;
  +
  mutex_lock(n-dev.mutex);
  if ((features  (1  VHOST_F_LOG_ALL)) 
  !vhost_log_access_ok(n-dev)) {
 
 Above seems to prevent users from specifying either
 VIRTIO_F_VERSION_1 or VHOST_F_SET_ENDIAN_LEGACY.
 Does it actually work?
 

Arggg no it doesn't *of course*... I've added these bogus checks lately
and didn't re-test :(

  diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
  index 2ee2826..60a0f32 100644
  --- a/drivers/vhost/vhost.c
  +++ b/drivers/vhost/vhost.c
  @@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
  vq-call = NULL;
  vq-log_ctx = NULL;
  vq-memory = NULL;
  +   vq-legacy_big_endian = false;
   }
   
   static int vhost_worker(void *data)
  @@ -806,6 +807,24 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, 
  void __user *argp)
  } else
  filep = eventfp;
  break;
  +#ifdef CONFIG_VHOST_SET_ENDIAN_LEGACY
  +   case VHOST_SET_VRING_ENDIAN_LEGACY:
  +   {
  +   struct vhost_vring_endian e;
  +
  +   if (!vhost_has_feature(vq, VHOST_F_SET_ENDIAN_LEGACY)) {
  +   r = -EINVAL;
  +   break;
  +   }
  +
  +   if (copy_from_user(e, argp, sizeof(e))) {
  +   r = -EFAULT;
  +   break;
  +   }
  +   vq

Re: [PATCH] kvm: move advertising of KVM_CAP_IRQFD to common code

[Greg Kurz]

On Thu,  5 Mar 2015 11:54:46 +0100
Paolo Bonzini pbonz...@redhat.com wrote:
 POWER supports irqfds but forgot to advertise them.  Some userspace does
 not check for the capability, but others check it---thus they work on
 x86 and s390 but not POWER.
 
 To avoid that other architectures in the future make the same mistake, let
 common code handle KVM_CAP_IRQFD the same way as KVM_CAP_IRQFD_RESAMPLE.
 
 Reported-by: Greg Kurz gk...@linux.vnet.ibm.com
 Cc: sta...@vger.kernel.org
 Fixes: 297e21053a52f060944e9f0de4c64fad9bcd72fc
 Signed-off-by: Paolo Bonzini pbonz...@redhat.com
 ---

Thanks !

Tested-by: Greg Kurz gk...@linux.vnet.ibm.com

   Marcelo, please apply this for 4.0.
 ---
  arch/s390/kvm/kvm-s390.c | 1 -
  arch/x86/kvm/x86.c   | 1 -
  virt/kvm/kvm_main.c  | 1 +
  3 files changed, 1 insertion(+), 2 deletions(-)
 
 diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
 index 0c3623927563..17277968e50a 100644
 --- a/arch/s390/kvm/kvm-s390.c
 +++ b/arch/s390/kvm/kvm-s390.c
 @@ -165,7 +165,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long 
 ext)
   case KVM_CAP_ONE_REG:
   case KVM_CAP_ENABLE_CAP:
   case KVM_CAP_S390_CSS_SUPPORT:
 - case KVM_CAP_IRQFD:
   case KVM_CAP_IOEVENTFD:
   case KVM_CAP_DEVICE_CTRL:
   case KVM_CAP_ENABLE_CAP_VM:
 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
 index bd7a70be41b3..32bf19ef3115 100644
 --- a/arch/x86/kvm/x86.c
 +++ b/arch/x86/kvm/x86.c
 @@ -2744,7 +2744,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long 
 ext)
   case KVM_CAP_USER_NMI:
   case KVM_CAP_REINJECT_CONTROL:
   case KVM_CAP_IRQ_INJECT_STATUS:
 - case KVM_CAP_IRQFD:
   case KVM_CAP_IOEVENTFD:
   case KVM_CAP_IOEVENTFD_NO_LENGTH:
   case KVM_CAP_PIT2:
 diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
 index a1093700f3a4..a2214d9609bd 100644
 --- a/virt/kvm/kvm_main.c
 +++ b/virt/kvm/kvm_main.c
 @@ -2492,6 +2492,7 @@ static long kvm_vm_ioctl_check_extension_generic(struct 
 kvm *kvm, long arg)
   case KVM_CAP_SIGNAL_MSI:
  #endif
  #ifdef CONFIG_HAVE_KVM_IRQFD
 + case KVM_CAP_IRQFD:
   case KVM_CAP_IRQFD_RESAMPLE:
  #endif
   case KVM_CAP_CHECK_EXTENSION_VM:

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Re: [PATCH 0/3] vhost_net: support for cross endian guests

[Greg Kurz]

On Sun, 22 Feb 2015 10:53:51 +0100
Michael S. Tsirkin m...@redhat.com wrote:
 On Fri, Feb 20, 2015 at 11:07:24AM +0100, Greg Kurz wrote:
  Hi,
  
  This patchset allows vhost_net to be used with legacy virtio
  when guest and host have a different endianness. It is based
  on previous work by Cédric Le Goater:
  
  https://www.mail-archive.com/kvm-ppc@vger.kernel.org/msg09848.html
  
  As suggested by MST:
  - the API now asks for a specific format (big endian) instead of the hint
whether byteswap is needed or not (patch 1)
  - rebased on top of the virtio-1 accessors (patch 2)
  
  Patch 3 is a separate fix: I think it is also valid for virtio-1.
 
 I don't think so. See e.g. this code in tun:
 gso.csum_offset = cpu_to_tun16(tun, skb-csum_offset);
 looks like it has the correct endian-ness for virtio-1.
 
 

Indeed. I will fix tun/macvtap as you suggested.

Thanks for the review.

--
Greg

 
  Please comment.
  
  ---
  
  Greg Kurz (3):
vhost: add VHOST_VRING_F_LEGACY_BIG_ENDIAN flag
vhost: add support for legacy virtio
vhost_net: fix virtio_net header endianness
  
  
   drivers/vhost/net.c|   32 ++--
   drivers/vhost/vhost.c  |6 +-
   drivers/vhost/vhost.h  |   23 +--
   include/uapi/linux/vhost.h |2 ++
   4 files changed, 50 insertions(+), 13 deletions(-)
  
  --
  Greg
 

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[PATCH 3/3] vhost_net: fix virtio_net header endianness

[Greg Kurz]

Without this patch, packets are being silently dropped by the tap backend.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/net.c |   32 ++--
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index afa06d2..2923eee 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -288,6 +288,16 @@ static void vhost_zerocopy_callback(struct ubuf_info 
*ubuf, bool success)
rcu_read_unlock_bh();
 }
 
+static void fix_virtio_net_hdr(struct vhost_virtqueue *vq)
+{
+   struct virtio_net_hdr *hdr = vq-iov[0].iov_base;
+
+   hdr-hdr_len = vhost16_to_cpu(vq, hdr-hdr_len);
+   hdr-gso_size = vhost16_to_cpu(vq, hdr-gso_size);
+   hdr-csum_start  = vhost16_to_cpu(vq, hdr-csum_start);
+   hdr-csum_offset = vhost16_to_cpu(vq, hdr-csum_offset);
+}
+
 /* Expects to be always run from workqueue - which acts as
  * read-size critical section for our kind of RCU. */
 static void handle_tx(struct vhost_net *net)
@@ -352,6 +362,10 @@ static void handle_tx(struct vhost_net *net)
   out %d, int %d\n, out, in);
break;
}
+
+   if (!hdr_size)
+   fix_virtio_net_hdr(vq);
+
/* Skip header. TODO: support TSO. */
len = iov_length(vq-iov, out);
iov_iter_init(msg.msg_iter, WRITE, vq-iov, out, len);
@@ -609,12 +623,18 @@ static void handle_rx(struct vhost_net *net)
continue;
}
/* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
-   if (unlikely(vhost_hlen) 
-   copy_to_iter(hdr, sizeof(hdr), fixup) != sizeof(hdr)) {
-   vq_err(vq, Unable to write vnet_hdr at addr %p\n,
-  vq-iov-iov_base);
-   break;
-   }
+   if (unlikely(vhost_hlen)) {
+   size_t len = copy_to_iter(hdr, sizeof(hdr), fixup);
+
+   if (len != sizeof(hdr)) {
+   vq_err(vq,
+  Unable to write vnet_hdr at addr %p\n,
+  vq-iov-iov_base);
+   break;
+   }
+   } else
+   fix_virtio_net_hdr(vq);
+
/* TODO: Should check and handle checksum. */
 
num_buffers = cpu_to_vhost16(vq, headcount);

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[PATCH 2/3] vhost: add support for legacy virtio

[Greg Kurz]

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/vhost.h |   20 ++--
 1 file changed, 14 insertions(+), 6 deletions(-)

Michael,

The vhost_is_little_endian() helper adds unconditionnal overhead to fixed
endian architectures: that is all architectures except arm and ppc64. This
was addressed in QEMU with a TARGET_IS_BIENDIAN macro. Please give an
advice about how to address this in the vhost code.

Thanks.

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index ce2c68e..21e7d6a 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -176,34 +176,42 @@ static inline bool vhost_has_feature(struct 
vhost_virtqueue *vq, int bit)
return vq-acked_features  (1ULL  bit);
 }
 
+static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
+{
+   if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
+   return true;
+   else
+   return !vq-legacy_big_endian;
+}
+
 /* Memory accessors */
 static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
 {
-   return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio16_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio16 cpu_to_vhost16(struct vhost_virtqueue *vq, u16 val)
 {
-   return __cpu_to_virtio16(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio16(vhost_is_little_endian(vq), val);
 }
 
 static inline u32 vhost32_to_cpu(struct vhost_virtqueue *vq, __virtio32 val)
 {
-   return __virtio32_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio32_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio32 cpu_to_vhost32(struct vhost_virtqueue *vq, u32 val)
 {
-   return __cpu_to_virtio32(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio32(vhost_is_little_endian(vq), val);
 }
 
 static inline u64 vhost64_to_cpu(struct vhost_virtqueue *vq, __virtio64 val)
 {
-   return __virtio64_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __virtio64_to_cpu(vhost_is_little_endian(vq), val);
 }
 
 static inline __virtio64 cpu_to_vhost64(struct vhost_virtqueue *vq, u64 val)
 {
-   return __cpu_to_virtio64(vhost_has_feature(vq, VIRTIO_F_VERSION_1), 
val);
+   return __cpu_to_virtio64(vhost_is_little_endian(vq), val);
 }
 #endif

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[PATCH 1/3] vhost: add VHOST_VRING_F_LEGACY_BIG_ENDIAN flag

[Greg Kurz]

The VHOST_VRING_F_LEGACY_BIG_ENDIAN flag informs the kernel that the
associated device is big endian. Of course, this only makes sense for
legacy virtio devices since modern virtio devices are always little
endian.

It will be used by the vhost memory accessors to byteswap vring data when
we have a legacy device, in case host and guest endianness differ.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 drivers/vhost/vhost.c  |6 +-
 drivers/vhost/vhost.h  |3 +++
 include/uapi/linux/vhost.h |2 ++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2ee2826..dad3c37 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -199,6 +199,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
vq-call = NULL;
vq-log_ctx = NULL;
vq-memory = NULL;
+   vq-legacy_big_endian = false;
 }
 
 static int vhost_worker(void *data)
@@ -701,7 +702,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void 
__user *argp)
r = -EFAULT;
break;
}
-   if (a.flags  ~(0x1  VHOST_VRING_F_LOG)) {
+   if (a.flags  ~(0x1  VHOST_VRING_F_LOG|
+   0x1  VHOST_VRING_F_LEGACY_BIG_ENDIAN)) {
r = -EOPNOTSUPP;
break;
}
@@ -751,6 +753,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void 
__user *argp)
vq-avail = (void __user *)(unsigned long)a.avail_user_addr;
vq-log_addr = a.log_guest_addr;
vq-used = (void __user *)(unsigned long)a.used_user_addr;
+   vq-legacy_big_endian =
+   !!(a.flags  (0x1  VHOST_VRING_F_LEGACY_BIG_ENDIAN));
break;
case VHOST_SET_VRING_KICK:
if (copy_from_user(f, argp, sizeof f)) {
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8c1c792..ce2c68e 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -106,6 +106,9 @@ struct vhost_virtqueue {
/* Log write descriptors */
void __user *log_base;
struct vhost_log *log;
+
+   /* We need to know the device endianness with legacy virtio. */
+   bool legacy_big_endian;
 };
 
 struct vhost_dev {
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index bb6a5b4..0bf4491 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -34,6 +34,8 @@ struct vhost_vring_addr {
/* Flag values: */
/* Whether log address is valid. If set enables logging. */
 #define VHOST_VRING_F_LOG 0
+   /* Whether we have a big-endian legacy virtio device. */
+#define VHOST_VRING_F_LEGACY_BIG_ENDIAN 1
 
/* Start of array of descriptors (virtually contiguous) */
__u64 desc_user_addr;

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[PATCH 0/3] vhost_net: support for cross endian guests

[Greg Kurz]

Hi,

This patchset allows vhost_net to be used with legacy virtio
when guest and host have a different endianness. It is based
on previous work by Cédric Le Goater:

https://www.mail-archive.com/kvm-ppc@vger.kernel.org/msg09848.html

As suggested by MST:
- the API now asks for a specific format (big endian) instead of the hint
  whether byteswap is needed or not (patch 1)
- rebased on top of the virtio-1 accessors (patch 2)

Patch 3 is a separate fix: I think it is also valid for virtio-1.

Please comment.

---

Greg Kurz (3):
  vhost: add VHOST_VRING_F_LEGACY_BIG_ENDIAN flag
  vhost: add support for legacy virtio
  vhost_net: fix virtio_net header endianness


 drivers/vhost/net.c|   32 ++--
 drivers/vhost/vhost.c  |6 +-
 drivers/vhost/vhost.h  |   23 +--
 include/uapi/linux/vhost.h |2 ++
 4 files changed, 50 insertions(+), 13 deletions(-)

--
Greg

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Re: [PATCH v8 34/50] vhost/net: virtio 1.0 byte swap

[Greg Kurz]

On Tue, 06 Jan 2015 16:55:30 -0700
Alex Williamson alex.william...@redhat.com wrote:

 On Mon, 2014-12-01 at 18:05 +0200, Michael S. Tsirkin wrote:
  I had to add an explicit tag to suppress compiler warning:
  gcc isn't smart enough to notice that
  len is always initialized since function is called with size  0.
 
 I'm getting a panic inside a guest when this change is applied on the
 host.  I identified this patch via bisect and confirmed by reverting it
 from v3.19-rc2.  Guest is centos6.  Thanks,
 
 Alex
 
 commit 8b38694a2dc8b18374310df50174f1e4376d6824
 Author: Michael S. Tsirkin m...@redhat.com
 Date:   Fri Oct 24 14:19:48 2014 +0300
 
 vhost/net: virtio 1.0 byte swap
 
 I had to add an explicit tag to suppress compiler warning:
 gcc isn't smart enough to notice that
 len is always initialized since function is called with size  0.
 
 Signed-off-by: Michael S. Tsirkin m...@redhat.com
 Reviewed-by: Cornelia Huck cornelia.h...@de.ibm.com
 

This chunk looks suspicious:

-   heads[headcount - 1].len += datalen;
+   heads[headcount - 1].len = cpu_to_vhost32(vq, len - datalen);

s/len - datalen/len + datalen/ ?

 XML chunk:
 
 interface type='direct'
   mac address='52:54:00:64:f3:34'/
   source dev='iscsinet0' mode='bridge'/
   model type='virtio'/
   address type='pci' domain='0x' bus='0x00' slot='0x03' 
 function='0x0'/
 /interface
 
 Panic log:
 
 1BUG: unable to handle kernel NULL pointer dereference at 0010
 1IP: [a0079469] virtnet_poll+0x4f9/0x910 [virtio_net]
 4PGD 1aa2f4067 PUD 1aa2f5067 PMD 0 
 4Oops:  [#1] SMP 
 4last sysfs file: 
 /sys/devices/pci:00/:00:03.0/virtio0/net/eth9/ifindex
 4CPU 0 
 4Modules linked in: 8021q garp stp llc ipt_REJECT nf_conntrack_ipv4 
 nf_defrag_ipv4 iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 
 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 uinput 
 microcode snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_seq 
 snd_seq_device snd_pcm snd_timer snd soundcore snd_page_alloc igbvf 
 nvidia(P)(U) i2c_core tg3 ptp pps_core virtio_balloon virtio_net 
 virtio_console ext4 jbd2 mbcache virtio_blk virtio_pci virtio_ring virtio 
 pata_acpi ata_generic ata_piix dm_mirror dm_region_hash dm_log dm_mod [last 
 unloaded: speedstep_lib]
 4
 4Pid: 1374, comm: NetworkManager Tainted: P   ---
 2.6.32-431.23.3.el6.centos.plus.x86_64 #1 QEMU Standard PC (i440FX + PIIX, 
 1996)
 4RIP: 0010:[a0079469]  [a0079469] 
 virtnet_poll+0x4f9/0x910 [virtio_net]
 4RSP: 0018:880028203e48  EFLAGS: 00010246
 4RAX: 8801a3383d00 RBX: 8801a6aaf480 RCX: 8801aa20b6e0
 4RDX: 00c0 RSI: 8801a3383c00 RDI: 8801a3383cc0
 4RBP: 880028203ed8 R08: 009e R09: 8801aa1d800c
 4R10: 0218 R11:  R12: 8801aa20b6e0
 4R13:  R14:  R15: 
 4FS:  7febf114d800() GS:88002820() 
 knlGS:
 4CS:  0010 DS:  ES:  CR0: 80050033
 4CR2: 0010 CR3: 0001aa793000 CR4: 06f0
 4DR0:  DR1:  DR2: 
 4DR3:  DR6: 0ff0 DR7: 0400
 4Process NetworkManager (pid: 1374, threadinfo 8801a74ba000, task 
 8801a8d56040)
 4Stack:
 4 8801aa1d8000 009e 8801aa20b6e0 8801aa20b718
 4d 8801aa20b780 8801aa1d800c 8801a6aaf4b8 8801aa20b020
 4d 0080 8801aa20b708 0001 1f5981a830c8
 4Call Trace:
 4 IRQ 
 4 [8146ae33] net_rx_action+0x103/0x2f0
 4 [8107a5f1] __do_softirq+0xc1/0x1e0
 4 [8100c30c] ? call_softirq+0x1c/0x30
 4 [8100c30c] call_softirq+0x1c/0x30
 4 EOI 
 4 [8100fa75] ? do_softirq+0x65/0xa0
 4 [8107b2ea] local_bh_enable+0x9a/0xb0
 4 [a007813a] virtnet_napi_enable+0x4a/0x60 [virtio_net]
 4 [a0078ebf] virtnet_open+0x4f/0x60 [virtio_net]
 4 [81467691] dev_open+0xa1/0x100
 4 [81466751] dev_change_flags+0xa1/0x1d0
 4 [81474a59] do_setlink+0x169/0x8b0
 4 [814770b6] ? rtnl_fill_ifinfo+0x946/0xcb0
 4 [812a3d24] ? nla_parse+0x34/0x110
 4 [8147659e] rtnl_setlink+0xee/0x130
 4 [81475b67] rtnetlink_rcv_msg+0x2d7/0x340
 4 [81231e14] ? socket_has_perm+0x74/0x90
 4 [81475890] ? rtnetlink_rcv_msg+0x0/0x340
 4 [814910a9] netlink_rcv_skb+0xa9/0xd0
 4 [81475875] rtnetlink_rcv+0x25/0x40
 4 [81490cdb] netlink_unicast+0x2db/0x320
 4 [81491750] netlink_sendmsg+0x2c0/0x3d0
 4 [814520c3] sock_sendmsg+0x123/0x150
 4 [81453d73] ? sock_recvmsg+0x133/0x160
 4 [8109afa0] ? autoremove_wake_function+0x0/0x40
 4 [81136941] ? lru_cache_add_lru+0x21/0x40
 4 [8115522d] ? page_add_new_anon_rmap+0x9d/0xf0
 4 [8114aeef] ? 

Re: [PATCH RFC v3 07/12] dataplane: allow virtio-1 devices

[Greg Kurz]

On Wed, 26 Nov 2014 18:28:38 +0100
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 Handle endianness conversion for virtio-1 virtqueues correctly.
 
 Note that dataplane now needs to be built per-target.
 
 Signed-off-by: Cornelia Huck cornelia.h...@de.ibm.com

Build is ok now.

Acked-by: Greg Kurz gk...@linux.vnet.ibm.com

 ---
  hw/block/dataplane/virtio-blk.c   |4 +-
  hw/scsi/virtio-scsi-dataplane.c   |2 +-
  hw/virtio/Makefile.objs   |2 +-
  hw/virtio/dataplane/Makefile.objs |2 +-
  hw/virtio/dataplane/vring.c   |   86 
 ++---
  include/hw/virtio/dataplane/vring-accessors.h |   75 +
  include/hw/virtio/dataplane/vring.h   |   14 +---
  7 files changed, 131 insertions(+), 54 deletions(-)
  create mode 100644 include/hw/virtio/dataplane/vring-accessors.h
 
 diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
 index 1222a37..2d8cc15 100644
 --- a/hw/block/dataplane/virtio-blk.c
 +++ b/hw/block/dataplane/virtio-blk.c
 @@ -16,7 +16,9 @@
  #include qemu/iov.h
  #include qemu/thread.h
  #include qemu/error-report.h
 +#include hw/virtio/virtio-access.h
  #include hw/virtio/dataplane/vring.h
 +#include hw/virtio/dataplane/vring-accessors.h
  #include sysemu/block-backend.h
  #include hw/virtio/virtio-blk.h
  #include virtio-blk.h
 @@ -75,7 +77,7 @@ static void complete_request_vring(VirtIOBlockReq *req, 
 unsigned char status)
  VirtIOBlockDataPlane *s = req-dev-dataplane;
  stb_p(req-in-status, status);
 
 -vring_push(req-dev-dataplane-vring, req-elem,
 +vring_push(s-vdev, req-dev-dataplane-vring, req-elem,
 req-qiov.size + sizeof(*req-in));
 
  /* Suppress notification to guest by BH and its scheduled
 diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
 index 03a1e8c..418d73b 100644
 --- a/hw/scsi/virtio-scsi-dataplane.c
 +++ b/hw/scsi/virtio-scsi-dataplane.c
 @@ -94,7 +94,7 @@ void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
  {
  VirtIODevice *vdev = VIRTIO_DEVICE(req-vring-parent);
 
 -vring_push(req-vring-vring, req-elem,
 +vring_push(vdev, req-vring-vring, req-elem,
 req-qsgl.size + req-resp_iov.size);
 
  if (vring_should_notify(vdev, req-vring-vring)) {
 diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
 index d21c397..19b224a 100644
 --- a/hw/virtio/Makefile.objs
 +++ b/hw/virtio/Makefile.objs
 @@ -2,7 +2,7 @@ common-obj-y += virtio-rng.o
  common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
  common-obj-y += virtio-bus.o
  common-obj-y += virtio-mmio.o
 -common-obj-$(CONFIG_VIRTIO) += dataplane/
 +obj-$(CONFIG_VIRTIO) += dataplane/
 
  obj-y += virtio.o virtio-balloon.o 
  obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
 diff --git a/hw/virtio/dataplane/Makefile.objs 
 b/hw/virtio/dataplane/Makefile.objs
 index 9a8cfc0..753a9ca 100644
 --- a/hw/virtio/dataplane/Makefile.objs
 +++ b/hw/virtio/dataplane/Makefile.objs
 @@ -1 +1 @@
 -common-obj-y += vring.o
 +obj-y += vring.o
 diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
 index a051775..0da8d6b 100644
 --- a/hw/virtio/dataplane/vring.c
 +++ b/hw/virtio/dataplane/vring.c
 @@ -18,7 +18,9 @@
  #include hw/hw.h
  #include exec/memory.h
  #include exec/address-spaces.h
 +#include hw/virtio/virtio-access.h
  #include hw/virtio/dataplane/vring.h
 +#include hw/virtio/dataplane/vring-accessors.h
  #include qemu/error-report.h
 
  /* vring_map can be coupled with vring_unmap or (if you still have the
 @@ -83,7 +85,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
  vring_init(vring-vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
 
  vring-last_avail_idx = virtio_queue_get_last_avail_idx(vdev, n);
 -vring-last_used_idx = vring-vr.used-idx;
 +vring-last_used_idx = vring_get_used_idx(vdev, vring);
  vring-signalled_used = 0;
  vring-signalled_used_valid = false;
 
 @@ -104,7 +106,7 @@ void vring_teardown(Vring *vring, VirtIODevice *vdev, int 
 n)
  void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
  {
  if (!(vdev-guest_features[0]  (1  VIRTIO_RING_F_EVENT_IDX))) {
 -vring-vr.used-flags |= VRING_USED_F_NO_NOTIFY;
 +vring_set_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
  }
  }
 
 @@ -117,10 +119,10 @@ bool vring_enable_notification(VirtIODevice *vdev, 
 Vring *vring)
  if (vdev-guest_features[0]  (1  VIRTIO_RING_F_EVENT_IDX)) {
  vring_avail_event(vring-vr) = vring-vr.avail-idx;
  } else {
 -vring-vr.used-flags = ~VRING_USED_F_NO_NOTIFY;
 +vring_clear_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
  }
  smp_mb(); /* ensure update is seen before reading avail_idx */
 -return !vring_more_avail(vring);
 +return !vring_more_avail(vdev, vring);
  }
 
  /* This is stolen from linux/drivers/vhost/vhost.c:vhost_notify

Re: [Qemu-devel] [PATCH RFC v3 05/12] virtio: introduce legacy virtio devices

[Greg Kurz]

On Wed, 26 Nov 2014 18:28:36 +0100
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 Introduce a helper function to indicate  whether a virtio device is
 operating in legacy or virtio standard mode.
 
 It may be used to make decisions about the endianess of virtio accesses
 and other virtio-1 specific changes, enabling us to support transitional
 devices.
 
 Reviewed-by: Thomas Huth th...@linux.vnet.ibm.com
 Signed-off-by: Cornelia Huck cornelia.h...@de.ibm.com
 ---
  hw/virtio/virtio.c|6 +-
  include/hw/virtio/virtio-access.h |4 
  include/hw/virtio/virtio.h|   13 +++--
  3 files changed, 20 insertions(+), 3 deletions(-)
 
 diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
 index 2eb5d3c..4149f45 100644
 --- a/hw/virtio/virtio.c
 +++ b/hw/virtio/virtio.c
 @@ -883,7 +883,11 @@ static bool virtio_device_endian_needed(void *opaque)
  VirtIODevice *vdev = opaque;
 
  assert(vdev-device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
 -return vdev-device_endian != virtio_default_endian();
 +if (virtio_device_is_legacy(vdev)) {
 +return vdev-device_endian != virtio_default_endian();
 +}
 +/* Devices conforming to VIRTIO 1.0 or later are always LE. */
 +return vdev-device_endian != VIRTIO_DEVICE_ENDIAN_LITTLE;
  }
 

Sorry but I still don't understand why we need to stream the device_endian
subsection if we have a virtio-1 device... this field is only used on
legacy device paths. Can you share an example where it is needed ?

  static const VMStateDescription vmstate_virtio_device_endian = {
 diff --git a/include/hw/virtio/virtio-access.h 
 b/include/hw/virtio/virtio-access.h
 index 46456fd..c123ee0 100644
 --- a/include/hw/virtio/virtio-access.h
 +++ b/include/hw/virtio/virtio-access.h
 @@ -19,6 +19,10 @@
 
  static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
  {
 +if (!virtio_device_is_legacy(vdev)) {
 +/* Devices conforming to VIRTIO 1.0 or later are always LE. */
 +return false;
 +}
  #if defined(TARGET_IS_BIENDIAN)
  return virtio_is_big_endian(vdev);
  #elif defined(TARGET_WORDS_BIGENDIAN)
 diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
 index b408166..40e567c 100644
 --- a/include/hw/virtio/virtio.h
 +++ b/include/hw/virtio/virtio.h
 @@ -275,9 +275,18 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue 
 *vq, bool assign,
  void virtio_queue_notify_vq(VirtQueue *vq);
  void virtio_irq(VirtQueue *vq);
 
 +static inline bool virtio_device_is_legacy(VirtIODevice *vdev)
 +{
 +return !(vdev-guest_features[1]  (1  (VIRTIO_F_VERSION_1 - 32)));
 +}
 +
  static inline bool virtio_is_big_endian(VirtIODevice *vdev)
  {
 -assert(vdev-device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
 -return vdev-device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
 +if (virtio_device_is_legacy(vdev)) {
 +assert(vdev-device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
 +return vdev-device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
 +}
 +/* Devices conforming to VIRTIO 1.0 or later are always LE. */
 +return false;
  }
  #endif

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Re: [PATCH RFC v2 07/12] dataplane: allow virtio-1 devices

[Greg Kurz]

On Tue, 25 Nov 2014 14:24:18 +0100
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 Handle endianness conversion for virtio-1 virtqueues correctly.
 
 Note that dataplane now needs to be built per-target.
 
 Signed-off-by: Cornelia Huck cornelia.h...@de.ibm.com
 ---

We still have the same error as in your previous post...

In file included from include/hw/virtio/dataplane/vring.h:23:0,
 from include/hw/virtio/virtio-scsi.h:21,
 from hw/virtio/virtio-pci.c:24:
include/hw/virtio/virtio-access.h: In function ‘virtio_access_is_big_endian’:
include/hw/virtio/virtio-access.h:28:15: error: attempt to use poisoned 
TARGET_WORDS_BIGENDIAN
 #elif defined(TARGET_WORDS_BIGENDIAN)

Either build virtio-pci per-target or probably better move the target tainted
accessors to another file.

  hw/block/dataplane/virtio-blk.c |3 +-
  hw/scsi/virtio-scsi-dataplane.c |2 +-
  hw/virtio/Makefile.objs |2 +-
  hw/virtio/dataplane/Makefile.objs   |2 +-
  hw/virtio/dataplane/vring.c |   85 
 +++
  include/hw/virtio/dataplane/vring.h |   64 --
  6 files changed, 113 insertions(+), 45 deletions(-)
 
 diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
 index 1222a37..c25878c 100644
 --- a/hw/block/dataplane/virtio-blk.c
 +++ b/hw/block/dataplane/virtio-blk.c
 @@ -16,6 +16,7 @@
  #include qemu/iov.h
  #include qemu/thread.h
  #include qemu/error-report.h
 +#include hw/virtio/virtio-access.h
  #include hw/virtio/dataplane/vring.h
  #include sysemu/block-backend.h
  #include hw/virtio/virtio-blk.h
 @@ -75,7 +76,7 @@ static void complete_request_vring(VirtIOBlockReq *req, 
 unsigned char status)
  VirtIOBlockDataPlane *s = req-dev-dataplane;
  stb_p(req-in-status, status);
 
 -vring_push(req-dev-dataplane-vring, req-elem,
 +vring_push(s-vdev, req-dev-dataplane-vring, req-elem,
 req-qiov.size + sizeof(*req-in));
 
  /* Suppress notification to guest by BH and its scheduled
 diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
 index 03a1e8c..418d73b 100644
 --- a/hw/scsi/virtio-scsi-dataplane.c
 +++ b/hw/scsi/virtio-scsi-dataplane.c
 @@ -94,7 +94,7 @@ void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
  {
  VirtIODevice *vdev = VIRTIO_DEVICE(req-vring-parent);
 
 -vring_push(req-vring-vring, req-elem,
 +vring_push(vdev, req-vring-vring, req-elem,
 req-qsgl.size + req-resp_iov.size);
 
  if (vring_should_notify(vdev, req-vring-vring)) {
 diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
 index d21c397..19b224a 100644
 --- a/hw/virtio/Makefile.objs
 +++ b/hw/virtio/Makefile.objs
 @@ -2,7 +2,7 @@ common-obj-y += virtio-rng.o
  common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
  common-obj-y += virtio-bus.o
  common-obj-y += virtio-mmio.o
 -common-obj-$(CONFIG_VIRTIO) += dataplane/
 +obj-$(CONFIG_VIRTIO) += dataplane/
 
  obj-y += virtio.o virtio-balloon.o 
  obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
 diff --git a/hw/virtio/dataplane/Makefile.objs 
 b/hw/virtio/dataplane/Makefile.objs
 index 9a8cfc0..753a9ca 100644
 --- a/hw/virtio/dataplane/Makefile.objs
 +++ b/hw/virtio/dataplane/Makefile.objs
 @@ -1 +1 @@
 -common-obj-y += vring.o
 +obj-y += vring.o
 diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
 index a051775..69809ff 100644
 --- a/hw/virtio/dataplane/vring.c
 +++ b/hw/virtio/dataplane/vring.c
 @@ -18,6 +18,7 @@
  #include hw/hw.h
  #include exec/memory.h
  #include exec/address-spaces.h
 +#include hw/virtio/virtio-access.h
  #include hw/virtio/dataplane/vring.h
  #include qemu/error-report.h
 
 @@ -83,7 +84,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
  vring_init(vring-vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
 
  vring-last_avail_idx = virtio_queue_get_last_avail_idx(vdev, n);
 -vring-last_used_idx = vring-vr.used-idx;
 +vring-last_used_idx = vring_get_used_idx(vdev, vring);
  vring-signalled_used = 0;
  vring-signalled_used_valid = false;
 
 @@ -104,7 +105,7 @@ void vring_teardown(Vring *vring, VirtIODevice *vdev, int 
 n)
  void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
  {
  if (!(vdev-guest_features[0]  (1  VIRTIO_RING_F_EVENT_IDX))) {
 -vring-vr.used-flags |= VRING_USED_F_NO_NOTIFY;
 +vring_set_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
  }
  }
 
 @@ -117,10 +118,10 @@ bool vring_enable_notification(VirtIODevice *vdev, 
 Vring *vring)
  if (vdev-guest_features[0]  (1  VIRTIO_RING_F_EVENT_IDX)) {
  vring_avail_event(vring-vr) = vring-vr.avail-idx;
  } else {
 -vring-vr.used-flags = ~VRING_USED_F_NO_NOTIFY;
 +vring_clear_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
  }
  smp_mb(); /* ensure update is seen before reading avail_idx */
 -return !vring_more_avail(vring);
 +return 

Re: [Qemu-devel] [PATCH RFC 05/11] virtio: introduce legacy virtio devices

[Greg Kurz]

On Thu, 30 Oct 2014 19:02:01 +0100
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 On Tue, 28 Oct 2014 16:40:18 +0100
 Greg Kurz gk...@linux.vnet.ibm.com wrote:
 
  On Tue,  7 Oct 2014 16:40:01 +0200
  Cornelia Huck cornelia.h...@de.ibm.com wrote:
  
   Introduce a helper function to indicate  whether a virtio device is
   operating in legacy or virtio standard mode.
   
   It may be used to make decisions about the endianess of virtio accesses
   and other virtio-1 specific changes, enabling us to support transitional
   devices.
   
   Reviewed-by: Thomas Huth th...@linux.vnet.ibm.com
   Signed-off-by: Cornelia Huck cornelia.h...@de.ibm.com
   ---
hw/virtio/virtio.c|6 +-
include/hw/virtio/virtio-access.h |4 
include/hw/virtio/virtio.h|   13 +++--
3 files changed, 20 insertions(+), 3 deletions(-)
   
   diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
   index 7aaa953..e6ae3a0 100644
   --- a/hw/virtio/virtio.c
   +++ b/hw/virtio/virtio.c
   @@ -883,7 +883,11 @@ static bool virtio_device_endian_needed(void *opaque)
VirtIODevice *vdev = opaque;
   
assert(vdev-device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
   -return vdev-device_endian != virtio_default_endian();
   +if (virtio_device_is_legacy(vdev)) {
   +return vdev-device_endian != virtio_default_endian();
   +}
   +/* Devices conforming to VIRTIO 1.0 or later are always LE. */
   +return vdev-device_endian != VIRTIO_DEVICE_ENDIAN_LITTLE;
}
   
  
  Shouldn't we have some code doing the following somewhere ?
  
  if (!virtio_device_is_legacy(vdev)) {
  vdev-device_endian = VIRTIO_DEVICE_ENDIAN_LITTLE;
  }
  
  also, since virtio-1 is LE only, do we expect device_endian to
  be different from VIRTIO_DEVICE_ENDIAN_LITTLE ?
 
 device_endian should not depend on whether the device is legacy or not.
 virtio_is_big_endian always returns false for virtio-1 devices, though.

Sorry, I had missed the virtio_is_big_endian() change: it that makes
device_endian a legacy virtio only matter. 
So why would we care to migrate the endian subsection when we have a
virtio-1 device ?  Shouldn't virtio_device_endian_needed() return false
for virtio-1 ?

--
Greg

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Re: [Qemu-devel] [PATCH RFC 07/11] dataplane: allow virtio-1 devices

[Greg Kurz]

On Tue,  7 Oct 2014 16:40:03 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 Handle endianness conversion for virtio-1 virtqueues correctly.
 
 Note that dataplane now needs to be built per-target.
 

It also affects hw/virtio/virtio-pci.c:

In file included from include/hw/virtio/dataplane/vring.h:23:0,
 from include/hw/virtio/virtio-scsi.h:21,
 from hw/virtio/virtio-pci.c:24:
include/hw/virtio/virtio-access.h: In function ‘virtio_access_is_big_endian’:
include/hw/virtio/virtio-access.h:28:15: error: attempt to use poisoned 
TARGET_WORDS_BIGENDIAN
 #elif defined(TARGET_WORDS_BIGENDIAN)
   ^

FWIW when I added endian ambivalent support to virtio, I remember *some people*
getting angry at the idea of turning common code into per-target... :)

See comment below.

 Signed-off-by: Cornelia Huck cornelia.h...@de.ibm.com
 ---
  hw/block/dataplane/virtio-blk.c |3 +-
  hw/scsi/virtio-scsi-dataplane.c |2 +-
  hw/virtio/Makefile.objs |2 +-
  hw/virtio/dataplane/Makefile.objs   |2 +-
  hw/virtio/dataplane/vring.c |   85 
 +++
  include/hw/virtio/dataplane/vring.h |   64 --
  6 files changed, 113 insertions(+), 45 deletions(-)
 
 diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
 index 5458f9d..eb45a3d 100644
 --- a/hw/block/dataplane/virtio-blk.c
 +++ b/hw/block/dataplane/virtio-blk.c
 @@ -16,6 +16,7 @@
  #include qemu/iov.h
  #include qemu/thread.h
  #include qemu/error-report.h
 +#include hw/virtio/virtio-access.h
  #include hw/virtio/dataplane/vring.h
  #include block/block.h
  #include hw/virtio/virtio-blk.h
 @@ -75,7 +76,7 @@ static void complete_request_vring(VirtIOBlockReq *req, 
 unsigned char status)
  VirtIOBlockDataPlane *s = req-dev-dataplane;
  stb_p(req-in-status, status);
 
 -vring_push(req-dev-dataplane-vring, req-elem,
 +vring_push(s-vdev, req-dev-dataplane-vring, req-elem,
 req-qiov.size + sizeof(*req-in));
 
  /* Suppress notification to guest by BH and its scheduled
 diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
 index b778e05..3e2b706 100644
 --- a/hw/scsi/virtio-scsi-dataplane.c
 +++ b/hw/scsi/virtio-scsi-dataplane.c
 @@ -81,7 +81,7 @@ VirtIOSCSIReq *virtio_scsi_pop_req_vring(VirtIOSCSI *s,
 
  void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
  {
 -vring_push(req-vring-vring, req-elem,
 +vring_push((VirtIODevice *)req-dev, req-vring-vring, req-elem,
 req-qsgl.size + req-resp_iov.size);
  event_notifier_set(req-vring-guest_notifier);
  }
 diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
 index d21c397..19b224a 100644
 --- a/hw/virtio/Makefile.objs
 +++ b/hw/virtio/Makefile.objs
 @@ -2,7 +2,7 @@ common-obj-y += virtio-rng.o
  common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
  common-obj-y += virtio-bus.o
  common-obj-y += virtio-mmio.o
 -common-obj-$(CONFIG_VIRTIO) += dataplane/
 +obj-$(CONFIG_VIRTIO) += dataplane/
 
  obj-y += virtio.o virtio-balloon.o 
  obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
 diff --git a/hw/virtio/dataplane/Makefile.objs 
 b/hw/virtio/dataplane/Makefile.objs
 index 9a8cfc0..753a9ca 100644
 --- a/hw/virtio/dataplane/Makefile.objs
 +++ b/hw/virtio/dataplane/Makefile.objs
 @@ -1 +1 @@
 -common-obj-y += vring.o
 +obj-y += vring.o
 diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
 index b84957f..4624521 100644
 --- a/hw/virtio/dataplane/vring.c
 +++ b/hw/virtio/dataplane/vring.c
 @@ -18,6 +18,7 @@
  #include hw/hw.h
  #include exec/memory.h
  #include exec/address-spaces.h
 +#include hw/virtio/virtio-access.h
  #include hw/virtio/dataplane/vring.h
  #include qemu/error-report.h
 
 @@ -83,7 +84,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
  vring_init(vring-vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
 
  vring-last_avail_idx = virtio_queue_get_last_avail_idx(vdev, n);
 -vring-last_used_idx = vring-vr.used-idx;
 +vring-last_used_idx = vring_get_used_idx(vdev, vring);
  vring-signalled_used = 0;
  vring-signalled_used_valid = false;
 
 @@ -104,7 +105,7 @@ void vring_teardown(Vring *vring, VirtIODevice *vdev, int 
 n)
  void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
  {
  if (!(vdev-guest_features[0]  (1  VIRTIO_RING_F_EVENT_IDX))) {
 -vring-vr.used-flags |= VRING_USED_F_NO_NOTIFY;
 +vring_set_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
  }
  }
 
 @@ -117,10 +118,10 @@ bool vring_enable_notification(VirtIODevice *vdev, 
 Vring *vring)
  if (vdev-guest_features[0]  (1  VIRTIO_RING_F_EVENT_IDX)) {
  vring_avail_event(vring-vr) = vring-vr.avail-idx;
  } else {
 -vring-vr.used-flags = ~VRING_USED_F_NO_NOTIFY;
 +vring_clear_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
  }
  smp_mb(); /* ensure update is seen before 

Re: [Qemu-devel] [PATCH RFC 05/11] virtio: introduce legacy virtio devices

[Greg Kurz]

On Tue,  7 Oct 2014 16:40:01 +0200
Cornelia Huck cornelia.h...@de.ibm.com wrote:

 Introduce a helper function to indicate  whether a virtio device is
 operating in legacy or virtio standard mode.
 
 It may be used to make decisions about the endianess of virtio accesses
 and other virtio-1 specific changes, enabling us to support transitional
 devices.
 
 Reviewed-by: Thomas Huth th...@linux.vnet.ibm.com
 Signed-off-by: Cornelia Huck cornelia.h...@de.ibm.com
 ---
  hw/virtio/virtio.c|6 +-
  include/hw/virtio/virtio-access.h |4 
  include/hw/virtio/virtio.h|   13 +++--
  3 files changed, 20 insertions(+), 3 deletions(-)
 
 diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
 index 7aaa953..e6ae3a0 100644
 --- a/hw/virtio/virtio.c
 +++ b/hw/virtio/virtio.c
 @@ -883,7 +883,11 @@ static bool virtio_device_endian_needed(void *opaque)
  VirtIODevice *vdev = opaque;
 
  assert(vdev-device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
 -return vdev-device_endian != virtio_default_endian();
 +if (virtio_device_is_legacy(vdev)) {
 +return vdev-device_endian != virtio_default_endian();
 +}
 +/* Devices conforming to VIRTIO 1.0 or later are always LE. */
 +return vdev-device_endian != VIRTIO_DEVICE_ENDIAN_LITTLE;
  }
 

Shouldn't we have some code doing the following somewhere ?

if (!virtio_device_is_legacy(vdev)) {
vdev-device_endian = VIRTIO_DEVICE_ENDIAN_LITTLE;
}

also, since virtio-1 is LE only, do we expect device_endian to
be different from VIRTIO_DEVICE_ENDIAN_LITTLE ?


Cheers.

--
Greg

  static const VMStateDescription vmstate_virtio_device_endian = {
 diff --git a/include/hw/virtio/virtio-access.h 
 b/include/hw/virtio/virtio-access.h
 index 46456fd..c123ee0 100644
 --- a/include/hw/virtio/virtio-access.h
 +++ b/include/hw/virtio/virtio-access.h
 @@ -19,6 +19,10 @@
 
  static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
  {
 +if (!virtio_device_is_legacy(vdev)) {
 +/* Devices conforming to VIRTIO 1.0 or later are always LE. */
 +return false;
 +}
  #if defined(TARGET_IS_BIENDIAN)
  return virtio_is_big_endian(vdev);
  #elif defined(TARGET_WORDS_BIGENDIAN)
 diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
 index b408166..40e567c 100644
 --- a/include/hw/virtio/virtio.h
 +++ b/include/hw/virtio/virtio.h
 @@ -275,9 +275,18 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue 
 *vq, bool assign,
  void virtio_queue_notify_vq(VirtQueue *vq);
  void virtio_irq(VirtQueue *vq);
 
 +static inline bool virtio_device_is_legacy(VirtIODevice *vdev)
 +{
 +return !(vdev-guest_features[1]  (1  (VIRTIO_F_VERSION_1 - 32)));
 +}
 +
  static inline bool virtio_is_big_endian(VirtIODevice *vdev)
  {
 -assert(vdev-device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
 -return vdev-device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
 +if (virtio_device_is_legacy(vdev)) {
 +assert(vdev-device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN);
 +return vdev-device_endian == VIRTIO_DEVICE_ENDIAN_BIG;
 +}
 +/* Devices conforming to VIRTIO 1.0 or later are always LE. */
 +return false;
  }
  #endif

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Re: [PATCH v3 9/9] kvmtool: virtio: enable arm/arm64 support for bi-endianness

[Greg Kurz]

On Wed, 07 May 2014 10:52:01 +0100
Marc Zyngier marc.zyng...@arm.com wrote:

 On Wed, May 07 2014 at 10:34:30 am BST, Peter Maydell 
 peter.mayd...@linaro.org wrote:
  On 6 May 2014 19:38, Peter Maydell peter.mayd...@linaro.org wrote:
  On 6 May 2014 18:25, Marc Zyngier marc.zyng...@arm.com wrote:
  On Tue, May 06 2014 at  3:28:07 pm BST, Will Deacon will.dea...@arm.com 
  wrote:
  On Thu, Apr 24, 2014 at 07:17:23PM +0100, Marc Zyngier wrote:
  +reg.addr = (u64)data;
  +if (ioctl(vcpu-vcpu_fd, KVM_GET_ONE_REG, reg)  0)
  +die(KVM_GET_ONE_REG failed (SCTLR_EL1));
  +
  +return (data  SCTLR_EL1_EE_MASK) ? VIRTIO_ENDIAN_BE : 
  VIRTIO_ENDIAN_LE;
 
  This rules out guests where userspace and kernelspace can run with 
  different
  endinness. Whilst Linux doesn't currently do this, can we support it 
  here?
  It all gets a bit hairy if the guest is using a stage-1 SMMU to let
  userspace play with a virtio device...
 
  Yeah, I suppose we could check either EE or E0 depending on the mode
  when the access was made. We already have all the information, just need
  to handle the case. I'll respin the series.
 
  How virtio implementations should determine their endianness is
  a spec question, I think; at any rate QEMU and kvmtool ought to
  agree on how it's done. I think the most recent suggestion on the
  QEMU mailing list (for PPC) is that we should care about the
  guest kernel endianness, but I don't know if anybody thought of
  the pass-through-to-userspace usecase...
 
  Current opinion on the qemu-devel thread seems to be that we
  should just define that the endianness of the virtio device is
  the endianness of the guest kernel at the point where the guest
  triggers a reset of the virtio device by writing zero the QueuePFN
  or Status registers.
 
 On AArch32, we only have the CPSR.E bit to select the endiannes. Are we
 going to simply explode if the access comes from userspace?
 
 On AArch64, we can either select the kernel endianness, or userspace
 endianness. Are we going to go a different route just for the sake of
 enforcing kernel access?
 
 I'm inclined to think of userspace access as a valid use case.
 
   M.

All the fuzz is not really about enforcing kernel access... PPC also
has a current endianness selector (MSR_LE) but it only makes sense
if you are in the cpu context. Initial versions of the virtio biendian
support for QEMU PPC64 used an arbitrary cpu: in this case, the
only sensible thing to look at to support kernel based virtio is the 
interrupt endianness selector (LPCR_ILE), because if gives a safe
hint of the kernel endianness.

The patch set has evolved and now uses current_cpu at device reset time.
As a consequence, we are not necessarily tied to the kernel LPCR_ILE
selector I guess.

Cheers.

-- 
Gregory Kurz kurzg...@fr.ibm.com
 gk...@linux.vnet.ibm.com
Software Engineer @ IBM/Meiosys  http://www.ibm.com
Tel +33 (0)562 165 496

Anarchy is about taking complete responsibility for yourself.
Alan Moore.

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Re: [PATCH v3 9/9] kvmtool: virtio: enable arm/arm64 support for bi-endianness

[Greg Kurz]

On Wed, 7 May 2014 13:17:51 +0100
Peter Maydell peter.mayd...@linaro.org wrote:

 On 7 May 2014 12:04, Marc Zyngier marc.zyng...@arm.com wrote:
  On Wed, May 07 2014 at 11:40:54 am BST, Greg Kurz 
  gk...@linux.vnet.ibm.com wrote:
  All the fuzz is not really about enforcing kernel access... PPC also
  has a current endianness selector (MSR_LE) but it only makes sense
  if you are in the cpu context. Initial versions of the virtio biendian
  support for QEMU PPC64 used an arbitrary cpu: in this case, the
  only sensible thing to look at to support kernel based virtio is the
  interrupt endianness selector (LPCR_ILE), because if gives a safe
  hint of the kernel endianness.
 
  The patch set has evolved and now uses current_cpu at device reset time.
  As a consequence, we are not necessarily tied to the kernel LPCR_ILE
  selector I guess.
 
 Ah yes, I'd forgotten the history behind why we ended up looking
 at interrupt endianness.
 
  That makes a lot of sense, thanks for explaining that. You're basically
  doing the exact same thing we do with kvmtool on ARM. So if we have
  similar architectural features on both sides, why don't we support both
  kernel and userspace access?
 
 I don't think that we really need to get into whether userspace
 access is or is not a good idea -- endianness of the CPU which
 does the virtio reset at the point when it does that reset is a
 nice simple rule that should generalise across architectures,
 so why make it more complicated than that?
 
 thanks
 -- PMM
 

I am convinced... and feeling a bit guilty for all the noise ;)
I'll come with a new virtio patch set for QEMU that does just what
you say.

-- 
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 gk...@linux.vnet.ibm.com
Software Engineer @ IBM/Meiosys  http://www.ibm.com
Tel +33 (0)562 165 496

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Re: Preparing kvm/next for first pull request of 3.15 merge window

[Greg Kurz]

On Wed, 26 Mar 2014 10:19:52 +0100
Paolo Bonzini pbonz...@redhat.com wrote:
 Il 26/03/2014 04:51, Paul Mackerras ha scritto:
   I would like to know from ARM and PPC maintainers *now* (before the
   merge window opens) what will be in 3.15.  Also, PPC guys, please
   make sure the pull requests will be based on commit e724f080f5dd
   (KVM: PPC: Book3S HV: Fix register usage when loading/saving VRSAVE,
   2014-03-13).
  Alex has 5 commits in his kvm-ppc-queue branch that should go in.
  That tree is based on your kvm-3.14-2 tag, not on e724f080f5dd.
  Would you accept a pull request for that from me on Alex's behalf
  since he's away?
 
 Yes, of course.
 
  Do you need me to rebase it at all?
 
 These are:
 
 1ac4484979 PPC: KVM: Introduce hypervisor call H_GET_TCE
 e0a7be38c9 PPC: KVM: fix RESUME_GUEST check before returning from 
 kvmppc_run_core()
 013e98e657 PPC: KVM: fix RESUME_GUEST check before ending CEDE in 
 kvmppc_run_core()
 e8a7f11fe0 PPC: KVM: fix VCPU run for HV KVM (v2)
 26d96ec97c PPC: KVM: introduce helper to check RESUME_GUEST and related
 
 I would consider rebasing; but you know better than me the effect of the 
 two host-crash-fixing patches and how the testability/bisectability of 
 kvm-ppc-queue is affected.
 
 In particular, how likely is it that reverse-bisection (which commit 
 fixed the bug?) would end up on e724f080f5dd rather than one of the 
 four RESUME_GUEST commits?
 

Paul,

It is safe to merge e0a7be38c9, 013e98e657, e8a7f11fe0 and 26d96ec97c as
a single patch... thing I should I've done from the beginning I guess. :)

Cheers.

--
Greg

  There is also the set of 8 patches that I just posted and Scott
  acked.  I can make a branch based on e724f080f5dd and send you a pull
  request.
 
 Yes, thanks!
 
 Paolo
 
  Let me know what you would prefer regarding Alex's kvm-ppc-queue
  branch.
 
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-- 
Gregory Kurz kurzg...@fr.ibm.com
 gk...@linux.vnet.ibm.com
Software Engineer @ IBM/Meiosys  http://www.ibm.com
Tel +33 (0)562 165 496

Anarchy is about taking complete responsibility for yourself.
Alan Moore.

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Re: [PATCH 0/4] PPC: KVM: fix RESUME_GUEST checks

[Greg Kurz]

On Thu, 6 Feb 2014 18:39:30 +0100
Alexander Graf ag...@suse.de wrote:
 
 On 06.02.2014, at 17:36, Greg Kurz gk...@linux.vnet.ibm.com wrote:
 
  As discussed in this thread:
  
  http://patchwork.ozlabs.org/patch/309166/
  
  We need some consistency in the way we check whether the guest
  should resume or not because:
  - new RESUME_GUEST_XXX values may show up
  - more locations in KVM may need to perform a similar check
  
  This serie introduces a helper and patches the locations where it
  should be called. There is yet another location in __kvmppc_vcpu_run,
  but it is assembly and cannot call a C inlined function.
 
 Thanks, applied all to kvm-ppc-queue. I think the splitting on this one
 is quite excessive - a single patch would've done :).
 
 
 Alex
 

Heh... I paranoid ! :)

Thanks Alex !

--
Greg

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[PATCH 1/4] PPC: KVM: introduce helper to check RESUME_GUEST and related

[Greg Kurz]

There are some locations where we check if the return value of a service
indicates that we should resume the guest. This patch introduces a helper
to handle the two possible values we currently have:
- RESUME_GUEST
- RESUME_GUEST_NV

Since it only affects Book3S HV for now, the helper is added to
the kvm_book3s.h header file.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 arch/powerpc/include/asm/kvm_book3s.h |5 +
 1 file changed, 5 insertions(+)

diff --git a/arch/powerpc/include/asm/kvm_book3s.h 
b/arch/powerpc/include/asm/kvm_book3s.h
index 83851aa..bb1e38a 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -304,6 +304,11 @@ static inline ulong kvmppc_get_fault_dar(struct kvm_vcpu 
*vcpu)
return vcpu-arch.fault_dar;
 }
 
+static inline bool is_kvmppc_resume_guest(int r)
+{
+   return (r == RESUME_GUEST || r == RESUME_GUEST_NV);
+}
+
 /* Magic register values loaded into r3 and r4 before the 'sc' assembly
  * instruction for the OSI hypercalls */
 #define OSI_SC_MAGIC_R30x113724FA

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[PATCH 2/4] PPC: KVM: fix VCPU run for HV KVM (v2)

[Greg Kurz]

From: Alexey Kardashevskiy a...@ozlabs.ru

When write to MMIO happens and there is an ioeventfd for that and
is handled successfully, ioeventfd_write() returns 0 (success) and
kvmppc_handle_store() returns EMULATE_DONE. Then kvmppc_emulate_mmio()
converts EMULATE_DONE to RESUME_GUEST_NV and this broke from the loop.

This adds handling of RESUME_GUEST_NV in kvmppc_vcpu_run_hv().

changes in v2:
- as suggesed by Alex Graf on kvm-ppc@, do it with a
  helper

Cc: Michael S. Tsirkin m...@redhat.com
Suggested-by: Paul Mackerras pau...@samba.org
Signed-off-by: Alexey Kardashevskiy a...@ozlabs.ru
Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 arch/powerpc/kvm/book3s_hv.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 17fc949..d62dc6c 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1731,7 +1731,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct 
kvm_vcpu *vcpu)
vcpu-arch.fault_dar, vcpu-arch.fault_dsisr);
srcu_read_unlock(vcpu-kvm-srcu, srcu_idx);
}
-   } while (r == RESUME_GUEST);
+   } while (is_kvmppc_resume_guest(r));
 
  out:
vcpu-arch.state = KVMPPC_VCPU_NOTREADY;

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[PATCH 0/4] PPC: KVM: fix RESUME_GUEST checks

[Greg Kurz]

As discussed in this thread:

http://patchwork.ozlabs.org/patch/309166/

We need some consistency in the way we check whether the guest
should resume or not because:
- new RESUME_GUEST_XXX values may show up
- more locations in KVM may need to perform a similar check

This serie introduces a helper and patches the locations where it
should be called. There is yet another location in __kvmppc_vcpu_run,
but it is assembly and cannot call a C inlined function.

---

Alexey Kardashevskiy (1):
  PPC: KVM: fix VCPU run for HV KVM (v2)

Greg Kurz (3):
  PPC: KVM: introduce helper to check RESUME_GUEST and related
  PPC: KVM: fix RESUME_GUEST check before ending CEDE in kvmppc_run_core()
  PPC: KVM: fix RESUME_GUEST check before returning from kvmppc_run_core()


 arch/powerpc/include/asm/kvm_book3s.h |5 +
 arch/powerpc/kvm/book3s_hv.c  |6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

-- 
Greg Kurz

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[PATCH 4/4] PPC: KVM: fix RESUME_GUEST check before returning from kvmppc_run_core()

[Greg Kurz]

Let's use a helper for this, in case new RESUME_GUEST_XXX values
are introduced.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 arch/powerpc/kvm/book3s_hv.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 85df6a4..3b498d9 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1541,7 +1541,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
vc-vcore_state = VCORE_INACTIVE;
list_for_each_entry_safe(vcpu, vnext, vc-runnable_threads,
 arch.run_list) {
-   if (vcpu-arch.ret != RESUME_GUEST) {
+   if (!is_kvmppc_resume_guest(vcpu-arch.ret)) {
kvmppc_remove_runnable(vc, vcpu);
wake_up(vcpu-arch.cpu_run);
}

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[PATCH 3/4] PPC: KVM: fix RESUME_GUEST check before ending CEDE in kvmppc_run_core()

[Greg Kurz]

Let's use a helper for this, in case new RESUME_GUEST_XXX values
are introduced.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 arch/powerpc/kvm/book3s_hv.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index d62dc6c..85df6a4 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1530,7 +1530,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
vcpu-arch.trap = 0;
 
if (vcpu-arch.ceded) {
-   if (ret != RESUME_GUEST)
+   if (!is_kvmppc_resume_guest(ret))
kvmppc_end_cede(vcpu);
else
kvmppc_set_timer(vcpu);

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[PATCH 3/4] PPC: KVM: fix RESUME_GUEST check before ending CEDE in kvmppc_run_core()

[Greg Kurz]

Let's use a helper for this, in case new RESUME_GUEST_XXX values
are introduced.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 arch/powerpc/kvm/book3s_hv.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index d62dc6c..85df6a4 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1530,7 +1530,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
vcpu-arch.trap = 0;
 
if (vcpu-arch.ceded) {
-   if (ret != RESUME_GUEST)
+   if (!is_kvmppc_resume_guest(ret))
kvmppc_end_cede(vcpu);
else
kvmppc_set_timer(vcpu);

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[PATCH 1/4] PPC: KVM: introduce helper to check RESUME_GUEST and related

[Greg Kurz]

There are some locations where we check if the return value of a service
indicates that we should resume the guest. This patch introduces a helper
to handle the two possible values we currently have:
- RESUME_GUEST
- RESUME_GUEST_NV

Since it only affects Book3S HV for now, the helper is added to
the kvm_book3s.h header file.

Signed-off-by: Greg Kurz gk...@linux.vnet.ibm.com
---
 arch/powerpc/include/asm/kvm_book3s.h |5 +
 1 file changed, 5 insertions(+)

diff --git a/arch/powerpc/include/asm/kvm_book3s.h 
b/arch/powerpc/include/asm/kvm_book3s.h
index 83851aa..bb1e38a 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -304,6 +304,11 @@ static inline ulong kvmppc_get_fault_dar(struct kvm_vcpu 
*vcpu)
return vcpu-arch.fault_dar;
 }
 
+static inline bool is_kvmppc_resume_guest(int r)
+{
+   return (r == RESUME_GUEST || r == RESUME_GUEST_NV);
+}
+
 /* Magic register values loaded into r3 and r4 before the 'sc' assembly
  * instruction for the OSI hypercalls */
 #define OSI_SC_MAGIC_R30x113724FA

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[PATCH 0/4] PPC: KVM: fix RESUME_GUEST checks

[Greg Kurz]

As discussed in this thread:

http://patchwork.ozlabs.org/patch/309166/

We need some consistency in the way we check whether the guest
should resume or not because:
- new RESUME_GUEST_XXX values may show up
- more locations in KVM may need to perform a similar check

This serie introduces a helper and patches the locations where it
should be called. There is yet another location in __kvmppc_vcpu_run,
but it is assembly and cannot call a C inlined function.

---

Alexey Kardashevskiy (1):
  PPC: KVM: fix VCPU run for HV KVM (v2)

Greg Kurz (3):
  PPC: KVM: introduce helper to check RESUME_GUEST and related
  PPC: KVM: fix RESUME_GUEST check before ending CEDE in kvmppc_run_core()
  PPC: KVM: fix RESUME_GUEST check before returning from kvmppc_run_core()


 arch/powerpc/include/asm/kvm_book3s.h |5 +
 arch/powerpc/kvm/book3s_hv.c  |6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

-- 
Greg Kurz

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Re: [Qemu-ppc] KVM and variable-endianness guest CPUs

[Greg Kurz]

On Wed, 22 Jan 2014 20:25:05 -0800
Victor Kamensky victor.kamen...@linaro.org wrote:

 Hi Alex,
 
 Sorry, for delayed reply, I was focusing on discussion
 with Peter. Hope you and other folks may get something
 out of it :).
 
 Please see responses inline
 
 On 22 January 2014 02:52, Alexander Graf ag...@suse.de wrote:
 
  On 22.01.2014, at 08:26, Victor Kamensky victor.kamen...@linaro.org
  wrote:
 
  On 21 January 2014 22:41, Alexander Graf ag...@suse.de wrote:
 
 
  Native endian really is just a shortcut for target endian
  which is LE for ARM and BE for PPC. There shouldn't be
  a qemu-system-armeb or qemu-system-ppc64le.
 
  I disagree. Fully functional ARM BE system is what we've
  been working on for last few months. 'We' is Linaro
  Networking Group, Endian subteam and some other guys
  in ARM and across community. Why we do that is a bit
  beyond of this discussion.
 
  ARM BE patches for both V7 and V8 are already in mainline
  kernel. But ARM BE KVM host is broken now. It is known
  deficiency that I am trying to fix. Please look at [1]. Patches
  for V7 BE KVM were proposed and currently under active
  discussion. Currently I work on ARM V8 BE KVM changes.
 
  So native endian in ARM is value of CPSR register E bit.
  If it is off native endian is LE, if it is on it is BE.
 
  Once and if we agree on ARM BE KVM host changes, the
  next step would be patches in qemu one of which introduces
  qemu-system-armeb. Please see [2].
 
  I think we're facing an ideology conflict here. Yes, there
  should be a qemu-system-arm that is BE capable.
 
 Maybe it is not ideology conflict but rather terminology clarity
 issue :). I am not sure what do you mean by qemu-system-arm
 that is BE capable. In qemu build system there is just target
 name 'arm', which is ARM V7 cpu in LE mode, and 'armeb'
 target which is ARM V7 cpu in BE mode. That is true for a lot
 of open source packages. You could check [1] patch that
 introduces armeb target into qemu. Build for
 arm target produces qemu-system-arm executable that is
 marked 'ELF 32-bit LSB executable' and it could run on LE
 traditional ARM Linux. Build for armeb target produces
 qemu-system-armeb executable that is marked 'ELF 32-bit
 MSB executable' that can run on BE ARM Linux. armbe is
 nothing special here, just build option for qemu that should run
 on BE ARM Linux.
 

Hmmm... it looks like there is a confusion about the qemu command naming.
The -target suffix in qemu-system-target has nothing to do with the ELF
information of the command itself.

[greg@bahia ~]$ file `which qemu-system-arm`
/bin/qemu-system-arm: ELF 64-bit LSB shared object, x86-64, version 1
(SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32,
BuildID[sha1]=0xbcb974847daa8159c17ed74906cd5351387d4097, stripped

It is valid to create a new target if it is substantially different from
existing ones (ppc64 versus ppc for example). This is not the case with ARM
since it is the very same CPU that can switch endianess with the 'setend'
instruction (which needs anyway to be emulated when running in TCG mode).

qemu-system-arm is THE command that should be able to emulate an ARM cpu,
whether the guest does 'setend le' or 'setend be'.

 Both qemu-system-arm and qemu-system-armeb should
 be BE/LE capable. I.e either of them along with KVM could
 either run LE or BE guest. MarcZ demonstrated that this
 is possible. I've tested both LE and BE guests with
 qemu-system-arm running on traditional LE ARM Linux,
 effectively repeating Marc's setup but with qemu.
 And I did test with my patches both BE and LE guests with
 qemu-system-armeb running on BE ARM Linux.
 
  There
  should also be a qemu-system-ppc64 that is LE capable.
  But there is no point in changing the default endiannes
  for the virtual CPUs that we plug in there. Both CPUs are
  perfectly capable of running in LE or BE mode, the
  question is just what we declare the default.
 
 I am not sure, what you mean by default? Is it initial
 setting of CPSR E bit and 'cp15 c1, c0, 0' EE bit? Yes,
 the way it is currently implemented by committed
 qemu-system-arm, and proposed qemu-system-armeb
 patches, they are both off. I.e even qemu-system-armeb
 starts running vcpu in LE mode, exactly by very similar
 reason as desribed in your next paragraph
 qemu-system-armeb has tiny bootloader that starts
 in LE mode, jumps to kernel kernel switches cpu to
 run in BE mode 'setend be' and EE bit is set just
 before mmu is enabled.
 
  Think about the PPC bootstrap. We start off with a
  BE firmware, then boot into the Linux kernel which
  calls a hypercall to set the LE bit on every interrupt.
 
 We have very similar situation with BE ARM Linux.
 When we run ARM BE Linux we start with bootloader
 which is LE and then CPU issues 'setend be' very
 soon as it starts executing kernel code, all secondary
 CPUs issue 'setend be' when they go out of reset pen
 or bootmonitor sleep.
 
  But there's no reason this little endian kernel
  couldn't 

Re: [Qemu-ppc] [RFC] QEMU/KVM PowerPC: virtio and guest endianness

[Greg Kurz]

On Fri, 4 Oct 2013 13:43:38 +0200
Alexander Graf ag...@suse.de wrote:

 CC'ing qemu-devel - please use qemu-ppc@ only as a tag, every mail
 needs to go to qemu-devel as well.
 

Sure I will.

 On 03.10.2013, at 16:29, Greg Kurz wrote:
 [...]
  I have searched for an appropriate place to add the polling and I
  must admit I did not find any... I am no QEMU expert but I suspect
  we would need some kind of arch specific hook to be called from the
  virtio code to do this... :-\ I hope I am wrong, please correct me
  if so.
 
 Just put it into the normal register sync function and call
 cpu_synchronize_state() on virtio reset.
 

Thanks, I will look into that.

 
 We have to decide which scheme to follow. There are 2 way we can /
 should handle registers usually:
 
   a) owned by QEMU
   b) owned by KVM
 
 If they're owned by QEMU, every hypercall needs to go into QEMU which
 then propagates that change through an ioctl back into KVM. If
 they're owned by KVM, QEMU needs to fetch them whenever it needs to
 
 As a general rule of thumb path b is easier to hack up, path a is
 easier to maintain long term. Which is pretty much what you're seeing
 here.
 

Agreed.

  I have a better feeling for (2) because:
  - 2-liner patch in KVM
  - no extra code change in QEMU
  - already *partially* tested
 
 I don't understand. QEMU would get triggered, then have to propagate
 things back into KVM. We definitely do _not_ want KVM to do magic,
 then tell QEMU to handle a hypercall again.
 

My idea was to have KVM and QEMU be like *co-owners* of the LPCR
register... now I admit it was a bad idea ! :)

  Also, I understood Rusty is working on the next virtio specification
  which should address the endian issue: probably not worth to add too
  many temporary lines in the QEMU code...
 
 Does 3.13 support LE mode? Does 3.13 support the new and shiny virtio
 spec? There's a good chance we'd have to deal with guest kernels that
 can do LE, but not sane virtio.
 

I don't know any details about 3.13 but I guess you are right, it is
unlikely the guests will have it.

  Of course, I probably lack some essential knowledge that would be
  more favorable to (1)... so please comment and argue ! :)
 
 I think a 100% QEMU implementation that just goes through all vcpus
 and does a simple SET_ONE_REG for LPCR to set ILE would be the best.
 Anton's patch isn't in Linus' tree yet, right? So all it takes is a
 partial revert of that one to not handle the actual hypercall in KVM.
 And some code in kvmppc_set_lpcr() to also set intr_msr (not changing
 it is a bug today already).
 
 
 Alex
 
 

Thanks for your indications Alex.

Cheers.

--
Greg

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Re: [Qemu-ppc] [RFC] QEMU/KVM PowerPC: virtio and guest endianness

[Greg Kurz]

Answering to both Paul and Alex.

On Fri, 4 Oct 2013 13:54:25 +0200
Alexander Graf ag...@suse.de wrote:

 
 On 04.10.2013, at 13:53, Paul Mackerras wrote:
  
  I don't mind particularly whether H_SET_MODE for the endianness
  setting gets handled in the kernel or in QEMU, but I don't think it
  should be handled in both.  If you want QEMU to know about the
  endianness setting immediately, make the kernel version do nothing
  and get QEMU to handle it -- which if KVM is enabled will mean
  iterating over all vcpus and getting them all to send the new LPCR
  setting to the kernel via the SET_ONE_REG ioctl.
  
  However, I want the setting of breakpoint registers (CIABR and
  DAWR/X) via H_SET_MODE to happen in the kernel, preferably in real
  mode, since that can happen on context switch and thus needs to be
  quick.
 

Paul,

As far as virtio is concerned, QEMU only needs to know about the guest
endiannes if a virtio device shows up. The virtio reset flow is a
good candiadate for that.

 I don't want to see a single hypercall be split across the QEMU/KVM
 barrier. So if there's a reasonable incentive to handle H_SET_MODE in
 KVM, we should handle all of it in KVM.
 

Alex,

The appropriate solution would be then to let KVM implement the whole
H_SET_MODE hcall and own LPCR. QEMU will poll it with cpu_synchronize_state().
It seems to preserve all the requirements.

 
 Alex
 
 --

Thanks for your guidance.

Cheers.

--
Greg

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[RFC] QEMU/KVM PowerPC: virtio and guest endianness

[Greg Kurz]

Hi,

There have been some work on the topic lately but no agreement has
been reached yet. I want to consolidate the facts in a single thread of
mail and re-start the discussion. Please find below a recap of what we
have as of today:

From a virtio POV, guest endianness is reflected by the endianness of
the interrupt vectors (ILE bit in the LPCR register). The guest kernel
relies on the H_SET_MODE_RESOURCE_LE hcall to set this bit, early in the
boot process.

Rusty sent a patchset on qemu-devel@ to provide the necessary bits to
perform byteswap in the QEMU:

http://patchwork.ozlabs.org/patch/266451/
http://patchwork.ozlabs.org/patch/266452/
http://patchwork.ozlabs.org/patch/266450/
(plus other enablement patches for virtio drivers, not essential for
the discussion).

In non-KVM mode, QEMU implements the H_SET_MODE_RESOURCE_LE and updates
its internal value for LPCR when the guest requests it. Rusty's patchset
works out-of-the-box in this mode: I could successfully setup and use a
9p share over virtio transport (broader virtio testing still to be done
though).

When using KVM, the story is different : QEMU is not on this
endianness change flow anymore, providing KVM has the following
patch from Anton:

http://patchwork.ozlabs.org/patch/277079/

There are *at least* two approaches to bring back endianness knowledge
to QEMU: polling (1) and propagation (2).

(1) QEMU must retrieve LPCR from the kernel using the following API:

http://patchwork.ozlabs.org/patch/273029/

(2) KVM can resume execution to the host and thus propagating
H_SET_MODE_RESOURCE_LE to QEMU. Laurent came up with a patch on
linuxppc-dev@ to do this:

http://patchwork.ozlabs.org/patch/278590/

I would say (1) is a standard and sane way of addressing the issue:
since the LPCR register value is held by KVM, it makes sense to
introduce an API to get/set it. Then, it is up to QEMU to use this API.

We can dumbly do the polling in all the places where byteswapping
matters: it is clearly sub-optimized, especially since the LPCR_ILE bit
doesn't change so often. Rusty suggested we can retrieve it at virtio
device reset time and cache it, since an endianness change after the
devices have started to be used is non-sensical.

I have searched for an appropriate place to add the polling and I must
admit I did not find any... I am no QEMU expert but I suspect we would
need some kind of arch specific hook to be called from the virtio code
to do this... :-\ I hope I am wrong, please correct me if so.

On the other hand, (2) looks a bit hacky: KVM usually returns to the
host when it cannot fully handle the h_call. Propagating may look like
a useless path to follow from a KVM POV. From a QEMU POV, things are
different: propagation will trig the fallback code in QEMU, already
working in non-KVM mode. Nothing more to be done.

I have a better feeling for (2) because:
- 2-liner patch in KVM
- no extra code change in QEMU
- already *partially* tested

Also, I understood Rusty is working on the next virtio specification
which should address the endian issue: probably not worth to add too
many temporary lines in the QEMU code...

Of course, I probably lack some essential knowledge that would be
more favorable to (1)... so please comment and argue ! :)

Thanks.

--
Greg Kurz

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