Commit 93a15b58 authored Mar 19, 2017 by Alex Williamson Committed by Zhenyu Wang Mar 20, 2017

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>

parent 2958b901

drivers/gpu/drm/i915/gvt/kvmgt.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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);

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