Re: [PATCH] kvmgt: Hold struct kvm reference
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, &info->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. $gpg --keyserver wwwkeys.pgp.net --recv-keys 4D781827 signature.asc Description: PGP signature
Re: [PATCH] kvmgt: Hold struct kvm reference
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, &info->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
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, &info->track_node); + kvm_put_kvm(info->kvm); kvmgt_protect_table_destroy(info); gvt_cache_destroy(info->vgpu); vfree(info);