Re: [PATCH] kvmgt: Hold struct kvm reference

[Zhenyu Wang]

On 2017.03.20 14:58:06 +0800, Jike Song wrote:
> On 03/20/2017 10:38 AM, Alex Williamson wrote:
> > The kvmgt code keeps a pointer to the struct kvm associated with the
> > device, but doesn't actually hold a reference to it.  If we do unclean
> > shutdown testing (ie. killing the user process), then we can see the
> > kvm association to the device unset, which causes kvmgt to trigger a
> > device release via a work queue.  Naturally we cannot guarantee that
> > the cached struct kvm pointer is still valid at this point without
> > holding a reference.  The observed failure in this case is a stuck
> > cpu trying to acquire the spinlock from the invalid reference, but
> > other failure modes are clearly possible.  Hold a reference to avoid
> > this.
> > 
> > Signed-off-by: Alex Williamson 
> > Cc: sta...@vger.kernel.org #v4.10
> > Cc: Jike Song 
> > Cc: Paolo Bonzini 
> > Cc: Zhenyu Wang 
> > Cc: Zhi Wang 
> > ---
> 
> Reviewed-by: Jike Song 
> 
> Thanks for the fix!
> 

queued in fixes tree, thanks!

> 
> >  drivers/gpu/drm/i915/gvt/kvmgt.c |2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c 
> > b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > index 84d801638ede..142b8bd4ba6b 100644
> > --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> > +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > @@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
> > vgpu->handle = (unsigned long)info;
> > info->vgpu = vgpu;
> > info->kvm = kvm;
> > +   kvm_get_kvm(info->kvm);
> >  
> > kvmgt_protect_table_init(info);
> > gvt_cache_init(vgpu);
> > @@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info 
> > *info)
> > }
> >  
> > kvm_page_track_unregister_notifier(info->kvm, >track_node);
> > +   kvm_put_kvm(info->kvm);
> > kvmgt_protect_table_destroy(info);
> > gvt_cache_destroy(info->vgpu);
> > vfree(info);
> > 

-- 
Open Source Technology Center, Intel ltd.

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Re: [PATCH] kvmgt: Hold struct kvm reference

[Zhenyu Wang]

On 2017.03.20 14:58:06 +0800, Jike Song wrote:
> On 03/20/2017 10:38 AM, Alex Williamson wrote:
> > The kvmgt code keeps a pointer to the struct kvm associated with the
> > device, but doesn't actually hold a reference to it.  If we do unclean
> > shutdown testing (ie. killing the user process), then we can see the
> > kvm association to the device unset, which causes kvmgt to trigger a
> > device release via a work queue.  Naturally we cannot guarantee that
> > the cached struct kvm pointer is still valid at this point without
> > holding a reference.  The observed failure in this case is a stuck
> > cpu trying to acquire the spinlock from the invalid reference, but
> > other failure modes are clearly possible.  Hold a reference to avoid
> > this.
> > 
> > Signed-off-by: Alex Williamson 
> > Cc: sta...@vger.kernel.org #v4.10
> > Cc: Jike Song 
> > Cc: Paolo Bonzini 
> > Cc: Zhenyu Wang 
> > Cc: Zhi Wang 
> > ---
> 
> Reviewed-by: Jike Song 
> 
> Thanks for the fix!
> 

queued in fixes tree, thanks!

> 
> >  drivers/gpu/drm/i915/gvt/kvmgt.c |2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c 
> > b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > index 84d801638ede..142b8bd4ba6b 100644
> > --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> > +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> > @@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
> > vgpu->handle = (unsigned long)info;
> > info->vgpu = vgpu;
> > info->kvm = kvm;
> > +   kvm_get_kvm(info->kvm);
> >  
> > kvmgt_protect_table_init(info);
> > gvt_cache_init(vgpu);
> > @@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info 
> > *info)
> > }
> >  
> > kvm_page_track_unregister_notifier(info->kvm, >track_node);
> > +   kvm_put_kvm(info->kvm);
> > kvmgt_protect_table_destroy(info);
> > gvt_cache_destroy(info->vgpu);
> > vfree(info);
> > 

-- 
Open Source Technology Center, Intel ltd.

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Re: [PATCH] kvmgt: Hold struct kvm reference

[Jike Song]

On 03/20/2017 10:38 AM, Alex Williamson wrote:
> The kvmgt code keeps a pointer to the struct kvm associated with the
> device, but doesn't actually hold a reference to it.  If we do unclean
> shutdown testing (ie. killing the user process), then we can see the
> kvm association to the device unset, which causes kvmgt to trigger a
> device release via a work queue.  Naturally we cannot guarantee that
> the cached struct kvm pointer is still valid at this point without
> holding a reference.  The observed failure in this case is a stuck
> cpu trying to acquire the spinlock from the invalid reference, but
> other failure modes are clearly possible.  Hold a reference to avoid
> this.
> 
> Signed-off-by: Alex Williamson 
> Cc: sta...@vger.kernel.org #v4.10
> Cc: Jike Song 
> Cc: Paolo Bonzini 
> Cc: Zhenyu Wang 
> Cc: Zhi Wang 
> ---

Reviewed-by: Jike Song 

Thanks for the fix!

--
Thanks,
Jike

>  drivers/gpu/drm/i915/gvt/kvmgt.c |2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c 
> b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 84d801638ede..142b8bd4ba6b 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
>   vgpu->handle = (unsigned long)info;
>   info->vgpu = vgpu;
>   info->kvm = kvm;
> + kvm_get_kvm(info->kvm);
>  
>   kvmgt_protect_table_init(info);
>   gvt_cache_init(vgpu);
> @@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info 
> *info)
>   }
>  
>   kvm_page_track_unregister_notifier(info->kvm, >track_node);
> + kvm_put_kvm(info->kvm);
>   kvmgt_protect_table_destroy(info);
>   gvt_cache_destroy(info->vgpu);
>   vfree(info);
> 

Re: [PATCH] kvmgt: Hold struct kvm reference

[Jike Song]

On 03/20/2017 10:38 AM, Alex Williamson wrote:
> The kvmgt code keeps a pointer to the struct kvm associated with the
> device, but doesn't actually hold a reference to it.  If we do unclean
> shutdown testing (ie. killing the user process), then we can see the
> kvm association to the device unset, which causes kvmgt to trigger a
> device release via a work queue.  Naturally we cannot guarantee that
> the cached struct kvm pointer is still valid at this point without
> holding a reference.  The observed failure in this case is a stuck
> cpu trying to acquire the spinlock from the invalid reference, but
> other failure modes are clearly possible.  Hold a reference to avoid
> this.
> 
> Signed-off-by: Alex Williamson 
> Cc: sta...@vger.kernel.org #v4.10
> Cc: Jike Song 
> Cc: Paolo Bonzini 
> Cc: Zhenyu Wang 
> Cc: Zhi Wang 
> ---

Reviewed-by: Jike Song 

Thanks for the fix!

--
Thanks,
Jike

>  drivers/gpu/drm/i915/gvt/kvmgt.c |2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c 
> b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 84d801638ede..142b8bd4ba6b 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
>   vgpu->handle = (unsigned long)info;
>   info->vgpu = vgpu;
>   info->kvm = kvm;
> + kvm_get_kvm(info->kvm);
>  
>   kvmgt_protect_table_init(info);
>   gvt_cache_init(vgpu);
> @@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info 
> *info)
>   }
>  
>   kvm_page_track_unregister_notifier(info->kvm, >track_node);
> + kvm_put_kvm(info->kvm);
>   kvmgt_protect_table_destroy(info);
>   gvt_cache_destroy(info->vgpu);
>   vfree(info);
> 

[PATCH] kvmgt: Hold struct kvm reference

[Alex Williamson]

The kvmgt code keeps a pointer to the struct kvm associated with the
device, but doesn't actually hold a reference to it.  If we do unclean
shutdown testing (ie. killing the user process), then we can see the
kvm association to the device unset, which causes kvmgt to trigger a
device release via a work queue.  Naturally we cannot guarantee that
the cached struct kvm pointer is still valid at this point without
holding a reference.  The observed failure in this case is a stuck
cpu trying to acquire the spinlock from the invalid reference, but
other failure modes are clearly possible.  Hold a reference to avoid
this.

Signed-off-by: Alex Williamson 
Cc: sta...@vger.kernel.org #v4.10
Cc: Jike Song 
Cc: Paolo Bonzini 
Cc: Zhenyu Wang 
Cc: Zhi Wang 
---
 drivers/gpu/drm/i915/gvt/kvmgt.c |2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 84d801638ede..142b8bd4ba6b 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
vgpu->handle = (unsigned long)info;
info->vgpu = vgpu;
info->kvm = kvm;
+   kvm_get_kvm(info->kvm);
 
kvmgt_protect_table_init(info);
gvt_cache_init(vgpu);
@@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info 
*info)
}
 
kvm_page_track_unregister_notifier(info->kvm, >track_node);
+   kvm_put_kvm(info->kvm);
kvmgt_protect_table_destroy(info);
gvt_cache_destroy(info->vgpu);
vfree(info);

[PATCH] kvmgt: Hold struct kvm reference

[Alex Williamson]

The kvmgt code keeps a pointer to the struct kvm associated with the
device, but doesn't actually hold a reference to it.  If we do unclean
shutdown testing (ie. killing the user process), then we can see the
kvm association to the device unset, which causes kvmgt to trigger a
device release via a work queue.  Naturally we cannot guarantee that
the cached struct kvm pointer is still valid at this point without
holding a reference.  The observed failure in this case is a stuck
cpu trying to acquire the spinlock from the invalid reference, but
other failure modes are clearly possible.  Hold a reference to avoid
this.

Signed-off-by: Alex Williamson 
Cc: sta...@vger.kernel.org #v4.10
Cc: Jike Song 
Cc: Paolo Bonzini 
Cc: Zhenyu Wang 
Cc: Zhi Wang 
---
 drivers/gpu/drm/i915/gvt/kvmgt.c |2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 84d801638ede..142b8bd4ba6b 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1324,6 +1324,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev)
vgpu->handle = (unsigned long)info;
info->vgpu = vgpu;
info->kvm = kvm;
+   kvm_get_kvm(info->kvm);
 
kvmgt_protect_table_init(info);
gvt_cache_init(vgpu);
@@ -1343,6 +1344,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info 
*info)
}
 
kvm_page_track_unregister_notifier(info->kvm, >track_node);
+   kvm_put_kvm(info->kvm);
kvmgt_protect_table_destroy(info);
gvt_cache_destroy(info->vgpu);
vfree(info);