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Commit f16bd3dd authored by Chuanxiao Dong's avatar Chuanxiao Dong Committed by Zhenyu Wang
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drm/i915/gvt: Fix inconsistent locks holding sequence 



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: f30437c5 ("drm/i915/gvt: add KVMGT support")
Signed-off-by: default avatarChuanxiao Dong <chuanxiao.dong@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: stable@vger.kernel.org # v4.10+
Signed-off-by: default avatarZhenyu Wang <zhenyuw@linux.intel.com>
parent 62d02fd1

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

+9 −5
Original line number Diff line number Diff line
@@ -260,16 +260,20 @@ static void gvt_cache_destroy(struct intel_vgpu *vgpu) 
	struct device *dev = mdev_dev(vgpu->vdev.mdev);

	unsigned long gfn;



	for (;;) {

		mutex_lock(&vgpu->vdev.cache_lock);

	while ((node = rb_first(&vgpu->vdev.cache))) {

		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);

	}

}



static struct intel_vgpu_type *intel_gvt_find_vgpu_type(struct intel_gvt *gvt,