drm/i915/kvmgt: Hold struct kvm reference
authorAlex Williamson <alex.williamson@redhat.com>
Mon, 20 Mar 2017 02:38:40 +0000 (20:38 -0600)
committerZhenyu Wang <zhenyuw@linux.intel.com>
Mon, 20 Mar 2017 07:06:14 +0000 (15:06 +0800)
commit93a15b58cfb8a24e666ffca432f19fe65c1cd7d1
tree4bd94a8310c4943a62ba45a3a3ef2bd3eb8c6606
parent2958b9013fcbabeeba221161d0712f5259f1e15d
drm/i915/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 <alex.williamson@redhat.com>
Cc: stable@vger.kernel.org #v4.10
Cc: Jike Song <jike.song@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Reviewed-by: Jike Song <jike.song@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
drivers/gpu/drm/i915/gvt/kvmgt.c