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drm/i915/kvmgt: Hold struct kvm reference

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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>
This commit is contained in:
Alex Williamson 2017-03-19 20:38:40 -06:00 committed by Zhenyu Wang
parent 2958b9013f
commit 93a15b58cf
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/i915/gvt/kvmgt.c
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@ -1326,6 +1326,7 @@ 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);
@ -1347,6 +1348,7 @@ 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);