From: Chuanxiao Dong <chuanxiao.dong@intel.com>
Date: Mon, 26 Jun 2017 15:20:50 +0800
Subject: [PATCH] drm/i915/gvt: Fix inconsistent locks holding sequence
References: bnc#1060662
Patch-mainline: v4.12.4
Git-commit: f16bd3dda2c8bf6699e808cd9cc540cfab10e60e

commit f16bd3dda2c8bf6699e808cd9cc540cfab10e60e upstream.

There are two kinds of locking sequence.

One is in the thread which is started by vfio ioctl to do
the iommu unmapping. The locking sequence is:
	down_read(&group_lock) ----> mutex_lock(&cached_lock)

The other is in the vfio release thread which will unpin all
the cached pages. The lock sequence is:
	mutex_lock(&cached_lock) ---> down_read(&group_lock)

And, the cache_lock is used to protect the rb tree of the cache
node and doing vfio unpin doesn't require this lock. Move the
vfio unpin out of the cache_lock protected region.

v2:
- use for style instead of do{}while(1). (Zhenyu)

Fixes: f30437c5e7bf ("drm/i915/gvt: add KVMGT support")
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/gpu/drm/i915/gvt/kvmgt.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 1ae0b4083ce1..fd0c85f9ef3c 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -232,16 +232,20 @@ static void gvt_cache_destroy(struct intel_vgpu *vgpu)
 	struct device *dev = mdev_dev(vgpu->vdev.mdev);
 	unsigned long gfn;
 
-	mutex_lock(&vgpu->vdev.cache_lock);
-	while ((node = rb_first(&vgpu->vdev.cache))) {
+	for (;;) {
+		mutex_lock(&vgpu->vdev.cache_lock);
+		node = rb_first(&vgpu->vdev.cache);
+		if (!node) {
+			mutex_unlock(&vgpu->vdev.cache_lock);
+			break;
+		}
 		dma = rb_entry(node, struct gvt_dma, node);
 		gvt_dma_unmap_iova(vgpu, dma->iova);
 		gfn = dma->gfn;
-
-		vfio_unpin_pages(dev, &gfn, 1);
 		__gvt_cache_remove_entry(vgpu, dma);
+		mutex_unlock(&vgpu->vdev.cache_lock);
+		vfio_unpin_pages(dev, &gfn, 1);
 	}
-	mutex_unlock(&vgpu->vdev.cache_lock);
 }
 
 static struct intel_vgpu_type *intel_gvt_find_vgpu_type(struct intel_gvt *gvt,
-- 
2.14.2