Patch "drm/i915/kvmgt: Hold struct kvm reference" has been added to the 4.10-stable tree

This is a note to let you know that I've just added the patch titled

drm/i915/kvmgt: Hold struct kvm reference

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-i915-kvmgt-hold-struct-kvm-reference.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Alex Williamson <[email protected]>
Date: Sun, 19 Mar 2017 20:38:40 -0600
Subject: drm/i915/kvmgt: Hold struct kvm reference

From: Alex Williamson <[email protected]>

commit 93a15b58cfb8a24e666ffca432f19fe65c1cd7d1 upstream.

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.

---
 drivers/gpu/drm/i915/gvt/kvmgt.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -1334,6 +1334,7 @@ static int kvmgt_guest_init(struct 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);

@@ -1353,6 +1354,7 @@ static bool kvmgt_guest_exit(struct kvmg
 	}
 
 	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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/drm-i915-kvmgt-hold-struct-kvm-reference.patch