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

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

[gregkh]

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 <stable@vger.kernel.org> know about it.


>From 93a15b58cfb8a24e666ffca432f19fe65c1cd7d1 Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson@redhat.com>
Date: Sun, 19 Mar 2017 20:38:40 -0600
Subject: drm/i915/kvmgt: Hold struct kvm reference

From: Alex Williamson <alex.williamson@redhat.com>

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.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -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 alex.williamson@redhat.com are

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