Re: [Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net

2018-09-21 Thread Michael S. Tsirkin 
On Fri, Sep 21, 2018 at 09:30:26AM +0200, Maxime Coquelin wrote:
> 
> 
> On 09/21/2018 04:33 AM, Jason Wang wrote:
> > 
> > 
> > On 2018年09月21日 04:39, Maxime Coquelin wrote:
> > > Hi Wei, Jason,
> > > 
> > > On 06/19/2018 09:53 AM, Wei Xu wrote:
> > > > On Wed, Jun 06, 2018 at 11:48:19AM +0800, Jason Wang wrote:
> > > > > 
> > > > > 
> > > > > On 2018年06月06日 03:08, w...@redhat.com wrote:
> > > > > > From: Wei Xu 
> > > > > > 
> > > > > > last_avail, avail_wrap_count, used_idx and used_wrap_count are
> > > > > > needed to support vhost-net backend, all these are either 16 or
> > > > > > bool variables, since state.num is 64bit wide, so here it is
> > > > > > possible to put them to the 'num' without introducing a new case
> > > > > > while handling ioctl.
> > > > > > 
> > > > > > Unload/Reload test has been done successfully with a
> > > > > > patch in vhost kernel.
> > > > > 
> > > > > You need a patch to enable vhost.
> > > > > 
> > > > > And I think you can only do it for vhost-kenrel now since vhost-user
> > > > > protocol needs some extension I believe.
> > > > 
> > > > OK.
> > > > 
> > > > > 
> > > > > > 
> > > > > > Signed-off-by: Wei Xu 
> > > > > > ---
> > > > > >   hw/virtio/virtio.c | 42 ++
> > > > > >   1 file changed, 34 insertions(+), 8 deletions(-)
> > > > > > 
> > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > > > > > index 4543974..153f6d7 100644
> > > > > > --- a/hw/virtio/virtio.c
> > > > > > +++ b/hw/virtio/virtio.c
> > > > > > @@ -2862,33 +2862,59 @@ hwaddr
> > > > > > virtio_queue_get_used_size(VirtIODevice *vdev, int n)
> > > > > >   }
> > > > > >   }
> > > > > > -uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> > > > > > +uint64_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> > > > > >   {
> > > > > > -    return vdev->vq[n].last_avail_idx;
> > > > > > +    uint64_t num;
> > > > > > +
> > > > > > +    num = vdev->vq[n].last_avail_idx;
> > > > > > +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> > > > > > +    num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 16;
> > > > > > +    num |= ((uint64_t)vdev->vq[n].used_idx) << 32;
> > > > > > +    num |= ((uint64_t)vdev->vq[n].used_wrap_counter) << 48;
> > > > > 
> > > > > So s.num is 32bit, I don't think this can even work.
> > > > 
> > > > I mistakenly checked out s.num is 64bit, will add a new case in
> > > > next version.
> > > 
> > > Wouldn't be enough to just get/set avail_wrap_counter?
> > > Something like this so that it fits into 32 bits:
> > >     if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> > >     num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 31;
> > >     }
> > > 
> > > 
> > > Regards,
> > > Maxime
> > 
> > Yes, actually, that's what I did for vhost kernel 
> > (https://github.com/jasowang/net/blob/packed-host/drivers/vhost/vhost.c#L1418)
> 
> Oh yes, I forgot on what I based my implementation on.
> Wei, Michael, do you agree with this? I will need to merge the Vhost
> patch in DPDK in the coming two weeks.
> 
> Regards,
> Maxime

It looks reasonable to me.

> > 
> > Thanks

Re: [Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net

2018-09-21 Thread Maxime Coquelin 




On 09/21/2018 04:33 AM, Jason Wang wrote:



On 2018年09月21日 04:39, Maxime Coquelin wrote:

Hi Wei, Jason,

On 06/19/2018 09:53 AM, Wei Xu wrote:

On Wed, Jun 06, 2018 at 11:48:19AM +0800, Jason Wang wrote:



On 2018年06月06日 03:08, w...@redhat.com wrote:

From: Wei Xu 

last_avail, avail_wrap_count, used_idx and used_wrap_count are
needed to support vhost-net backend, all these are either 16 or
bool variables, since state.num is 64bit wide, so here it is
possible to put them to the 'num' without introducing a new case
while handling ioctl.

Unload/Reload test has been done successfully with a patch in vhost 
kernel.


You need a patch to enable vhost.

And I think you can only do it for vhost-kenrel now since vhost-user
protocol needs some extension I believe.


OK.





Signed-off-by: Wei Xu 
---
  hw/virtio/virtio.c | 42 ++
  1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 4543974..153f6d7 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2862,33 +2862,59 @@ hwaddr 
virtio_queue_get_used_size(VirtIODevice *vdev, int n)

  }
  }
-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
+uint64_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
  {
-    return vdev->vq[n].last_avail_idx;
+    uint64_t num;
+
+    num = vdev->vq[n].last_avail_idx;
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+    num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 16;
+    num |= ((uint64_t)vdev->vq[n].used_idx) << 32;
+    num |= ((uint64_t)vdev->vq[n].used_wrap_counter) << 48;


So s.num is 32bit, I don't think this can even work.


I mistakenly checked out s.num is 64bit, will add a new case in next 
version.


Wouldn't be enough to just get/set avail_wrap_counter?
Something like this so that it fits into 32 bits:
    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
    num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 31;
    }


Regards,
Maxime


Yes, actually, that's what I did for vhost kernel 
(https://github.com/jasowang/net/blob/packed-host/drivers/vhost/vhost.c#L1418) 


Oh yes, I forgot on what I based my implementation on.
Wei, Michael, do you agree with this? I will need to merge the Vhost
patch in DPDK in the coming two weeks.

Regards,
Maxime



Thanks

Re: [Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net

2018-09-20 Thread Jason Wang 




On 2018年09月21日 04:39, Maxime Coquelin wrote:

Hi Wei, Jason,

On 06/19/2018 09:53 AM, Wei Xu wrote:

On Wed, Jun 06, 2018 at 11:48:19AM +0800, Jason Wang wrote:



On 2018年06月06日 03:08, w...@redhat.com wrote:

From: Wei Xu 

last_avail, avail_wrap_count, used_idx and used_wrap_count are
needed to support vhost-net backend, all these are either 16 or
bool variables, since state.num is 64bit wide, so here it is
possible to put them to the 'num' without introducing a new case
while handling ioctl.

Unload/Reload test has been done successfully with a patch in vhost 
kernel.


You need a patch to enable vhost.

And I think you can only do it for vhost-kenrel now since vhost-user
protocol needs some extension I believe.


OK.





Signed-off-by: Wei Xu 
---
  hw/virtio/virtio.c | 42 ++
  1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 4543974..153f6d7 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2862,33 +2862,59 @@ hwaddr 
virtio_queue_get_used_size(VirtIODevice *vdev, int n)

  }
  }
-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
+uint64_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
  {
-    return vdev->vq[n].last_avail_idx;
+    uint64_t num;
+
+    num = vdev->vq[n].last_avail_idx;
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+    num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 16;
+    num |= ((uint64_t)vdev->vq[n].used_idx) << 32;
+    num |= ((uint64_t)vdev->vq[n].used_wrap_counter) << 48;


So s.num is 32bit, I don't think this can even work.


I mistakenly checked out s.num is 64bit, will add a new case in next 
version.


Wouldn't be enough to just get/set avail_wrap_counter?
Something like this so that it fits into 32 bits:
    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
    num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 31;
    }


Regards,
Maxime


Yes, actually, that's what I did for vhost kernel 
(https://github.com/jasowang/net/blob/packed-host/drivers/vhost/vhost.c#L1418)


Thanks

Re: [Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net

2018-09-20 Thread Maxime Coquelin 

Hi Wei, Jason,

On 06/19/2018 09:53 AM, Wei Xu wrote:

On Wed, Jun 06, 2018 at 11:48:19AM +0800, Jason Wang wrote:



On 2018年06月06日 03:08, w...@redhat.com wrote:

From: Wei Xu 

last_avail, avail_wrap_count, used_idx and used_wrap_count are
needed to support vhost-net backend, all these are either 16 or
bool variables, since state.num is 64bit wide, so here it is
possible to put them to the 'num' without introducing a new case
while handling ioctl.

Unload/Reload test has been done successfully with a patch in vhost kernel.


You need a patch to enable vhost.

And I think you can only do it for vhost-kenrel now since vhost-user
protocol needs some extension I believe.


OK.





Signed-off-by: Wei Xu 
---
  hw/virtio/virtio.c | 42 ++
  1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 4543974..153f6d7 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2862,33 +2862,59 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, 
int n)
  }
  }
-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
+uint64_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
  {
-return vdev->vq[n].last_avail_idx;
+uint64_t num;
+
+num = vdev->vq[n].last_avail_idx;
+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 16;
+num |= ((uint64_t)vdev->vq[n].used_idx) << 32;
+num |= ((uint64_t)vdev->vq[n].used_wrap_counter) << 48;


So s.num is 32bit, I don't think this can even work.


I mistakenly checked out s.num is 64bit, will add a new case in next version.


Wouldn't be enough to just get/set avail_wrap_counter?
Something like this so that it fits into 32 bits:
if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 31;
}


Regards,
Maxime



Wei



Thanks


+}
+
+return num;
  }
-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint64_t num)
  {
-vdev->vq[n].last_avail_idx = idx;
-vdev->vq[n].shadow_avail_idx = idx;
+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx = 
(uint16_t)(num);
+
+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+vdev->vq[n].avail_wrap_counter = (uint16_t)(num >> 16);
+vdev->vq[n].used_idx = (uint16_t)(num >> 32);
+vdev->vq[n].used_wrap_counter = (uint16_t)(num >> 48);
+}
  }
  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
  {
  rcu_read_lock();
-if (vdev->vq[n].vring.desc) {
+if (!vdev->vq[n].vring.desc) {
+goto out;
+}
+
+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
  vdev->vq[n].last_avail_idx = vring_used_idx(>vq[n]);
-vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
  }
+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
+
+out:
  rcu_read_unlock();
  }
  void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
  {
  rcu_read_lock();
-if (vdev->vq[n].vring.desc) {
+if (!vdev->vq[n].vring.desc) {
+goto out;
+}
+
+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
  vdev->vq[n].used_idx = vring_used_idx(>vq[n]);
  }
+
+out:
  rcu_read_unlock();
  }

Re: [Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net

2018-06-19 Thread Wei Xu 
On Wed, Jun 06, 2018 at 11:48:19AM +0800, Jason Wang wrote:
> 
> 
> On 2018年06月06日 03:08, w...@redhat.com wrote:
> >From: Wei Xu 
> >
> >last_avail, avail_wrap_count, used_idx and used_wrap_count are
> >needed to support vhost-net backend, all these are either 16 or
> >bool variables, since state.num is 64bit wide, so here it is
> >possible to put them to the 'num' without introducing a new case
> >while handling ioctl.
> >
> >Unload/Reload test has been done successfully with a patch in vhost kernel.
> 
> You need a patch to enable vhost.
> 
> And I think you can only do it for vhost-kenrel now since vhost-user
> protocol needs some extension I believe.

OK.

> 
> >
> >Signed-off-by: Wei Xu 
> >---
> >  hw/virtio/virtio.c | 42 ++
> >  1 file changed, 34 insertions(+), 8 deletions(-)
> >
> >diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >index 4543974..153f6d7 100644
> >--- a/hw/virtio/virtio.c
> >+++ b/hw/virtio/virtio.c
> >@@ -2862,33 +2862,59 @@ hwaddr virtio_queue_get_used_size(VirtIODevice 
> >*vdev, int n)
> >  }
> >  }
> >-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> >+uint64_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> >  {
> >-return vdev->vq[n].last_avail_idx;
> >+uint64_t num;
> >+
> >+num = vdev->vq[n].last_avail_idx;
> >+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >+num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 16;
> >+num |= ((uint64_t)vdev->vq[n].used_idx) << 32;
> >+num |= ((uint64_t)vdev->vq[n].used_wrap_counter) << 48;
> 
> So s.num is 32bit, I don't think this can even work.

I mistakenly checked out s.num is 64bit, will add a new case in next version.

Wei

> 
> Thanks
> 
> >+}
> >+
> >+return num;
> >  }
> >-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t 
> >idx)
> >+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint64_t 
> >num)
> >  {
> >-vdev->vq[n].last_avail_idx = idx;
> >-vdev->vq[n].shadow_avail_idx = idx;
> >+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx = 
> >(uint16_t)(num);
> >+
> >+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >+vdev->vq[n].avail_wrap_counter = (uint16_t)(num >> 16);
> >+vdev->vq[n].used_idx = (uint16_t)(num >> 32);
> >+vdev->vq[n].used_wrap_counter = (uint16_t)(num >> 48);
> >+}
> >  }
> >  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
> >  {
> >  rcu_read_lock();
> >-if (vdev->vq[n].vring.desc) {
> >+if (!vdev->vq[n].vring.desc) {
> >+goto out;
> >+}
> >+
> >+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >  vdev->vq[n].last_avail_idx = vring_used_idx(>vq[n]);
> >-vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
> >  }
> >+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
> >+
> >+out:
> >  rcu_read_unlock();
> >  }
> >  void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
> >  {
> >  rcu_read_lock();
> >-if (vdev->vq[n].vring.desc) {
> >+if (!vdev->vq[n].vring.desc) {
> >+goto out;
> >+}
> >+
> >+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >  vdev->vq[n].used_idx = vring_used_idx(>vq[n]);
> >  }
> >+
> >+out:
> >  rcu_read_unlock();
> >  }
>

Re: [Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net

2018-06-05 Thread Jason Wang 




On 2018年06月06日 03:08, w...@redhat.com wrote:

From: Wei Xu 

last_avail, avail_wrap_count, used_idx and used_wrap_count are
needed to support vhost-net backend, all these are either 16 or
bool variables, since state.num is 64bit wide, so here it is
possible to put them to the 'num' without introducing a new case
while handling ioctl.

Unload/Reload test has been done successfully with a patch in vhost kernel.


You need a patch to enable vhost.

And I think you can only do it for vhost-kenrel now since vhost-user 
protocol needs some extension I believe.




Signed-off-by: Wei Xu 
---
  hw/virtio/virtio.c | 42 ++
  1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 4543974..153f6d7 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2862,33 +2862,59 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, 
int n)
  }
  }
  
-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)

+uint64_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
  {
-return vdev->vq[n].last_avail_idx;
+uint64_t num;
+
+num = vdev->vq[n].last_avail_idx;
+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 16;
+num |= ((uint64_t)vdev->vq[n].used_idx) << 32;
+num |= ((uint64_t)vdev->vq[n].used_wrap_counter) << 48;


So s.num is 32bit, I don't think this can even work.

Thanks


+}
+
+return num;
  }
  
-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)

+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint64_t num)
  {
-vdev->vq[n].last_avail_idx = idx;
-vdev->vq[n].shadow_avail_idx = idx;
+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx = 
(uint16_t)(num);
+
+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+vdev->vq[n].avail_wrap_counter = (uint16_t)(num >> 16);
+vdev->vq[n].used_idx = (uint16_t)(num >> 32);
+vdev->vq[n].used_wrap_counter = (uint16_t)(num >> 48);
+}
  }
  
  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)

  {
  rcu_read_lock();
-if (vdev->vq[n].vring.desc) {
+if (!vdev->vq[n].vring.desc) {
+goto out;
+}
+
+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
  vdev->vq[n].last_avail_idx = vring_used_idx(>vq[n]);
-vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
  }
+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
+
+out:
  rcu_read_unlock();
  }
  
  void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)

  {
  rcu_read_lock();
-if (vdev->vq[n].vring.desc) {
+if (!vdev->vq[n].vring.desc) {
+goto out;
+}
+
+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
  vdev->vq[n].used_idx = vring_used_idx(>vq[n]);
  }
+
+out:
  rcu_read_unlock();
  }

[Qemu-devel] [RFC v2 8/8] virtio: guest driver reload for vhost-net

2018-06-05 Thread wexu 
From: Wei Xu 

last_avail, avail_wrap_count, used_idx and used_wrap_count are
needed to support vhost-net backend, all these are either 16 or
bool variables, since state.num is 64bit wide, so here it is
possible to put them to the 'num' without introducing a new case
while handling ioctl.

Unload/Reload test has been done successfully with a patch in vhost kernel.

Signed-off-by: Wei Xu 
---
 hw/virtio/virtio.c | 42 ++
 1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 4543974..153f6d7 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2862,33 +2862,59 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, 
int n)
 }
 }
 
-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
+uint64_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
 {
-return vdev->vq[n].last_avail_idx;
+uint64_t num;
+
+num = vdev->vq[n].last_avail_idx;
+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+num |= ((uint64_t)vdev->vq[n].avail_wrap_counter) << 16;
+num |= ((uint64_t)vdev->vq[n].used_idx) << 32;
+num |= ((uint64_t)vdev->vq[n].used_wrap_counter) << 48;
+}
+
+return num;
 }
 
-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint64_t num)
 {
-vdev->vq[n].last_avail_idx = idx;
-vdev->vq[n].shadow_avail_idx = idx;
+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx = 
(uint16_t)(num);
+
+if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+vdev->vq[n].avail_wrap_counter = (uint16_t)(num >> 16);
+vdev->vq[n].used_idx = (uint16_t)(num >> 32);
+vdev->vq[n].used_wrap_counter = (uint16_t)(num >> 48);
+}
 }
 
 void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
 {
 rcu_read_lock();
-if (vdev->vq[n].vring.desc) {
+if (!vdev->vq[n].vring.desc) {
+goto out;
+}
+
+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
 vdev->vq[n].last_avail_idx = vring_used_idx(>vq[n]);
-vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
 }
+vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
+
+out:
 rcu_read_unlock();
 }
 
 void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
 {
 rcu_read_lock();
-if (vdev->vq[n].vring.desc) {
+if (!vdev->vq[n].vring.desc) {
+goto out;
+}
+
+if (!virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
 vdev->vq[n].used_idx = vring_used_idx(>vq[n]);
 }
+
+out:
 rcu_read_unlock();
 }
 
-- 
1.8.3.1