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 <[email protected]>
Cc: [email protected] #v4.10
Cc: Jike Song <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Zhenyu Wang <[email protected]>
Cc: Zhi Wang <[email protected]>
---
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, &info->track_node);
+ kvm_put_kvm(info->kvm);
kvmgt_protect_table_destroy(info);
gvt_cache_destroy(info->vgpu);
vfree(info);
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 <[email protected]>
> Cc: [email protected] #v4.10
> Cc: Jike Song <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Zhenyu Wang <[email protected]>
> Cc: Zhi Wang <[email protected]>
> ---
Reviewed-by: Jike Song <[email protected]>
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, &info->track_node);
> + kvm_put_kvm(info->kvm);
> kvmgt_protect_table_destroy(info);
> gvt_cache_destroy(info->vgpu);
> vfree(info);
>
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 <[email protected]>
> > Cc: [email protected] #v4.10
> > Cc: Jike Song <[email protected]>
> > Cc: Paolo Bonzini <[email protected]>
> > Cc: Zhenyu Wang <[email protected]>
> > Cc: Zhi Wang <[email protected]>
> > ---
>
> Reviewed-by: Jike Song <[email protected]>
>
> 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, &info->track_node);
> > + kvm_put_kvm(info->kvm);
> > kvmgt_protect_table_destroy(info);
> > gvt_cache_destroy(info->vgpu);
> > vfree(info);
> >
--
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