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 <alex.williamson@xxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx #v4.10 > Cc: Jike Song <jike.song@xxxxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx> > Cc: Zhi Wang <zhi.a.wang@xxxxxxxxx> > --- Reviewed-by: Jike Song <jike.song@xxxxxxxxx> 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); >
