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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: f30437c5e7 ("drm/i915/gvt: add KVMGT support")
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: stable@vger.kernel.org # v4.10+
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
This commit is contained in:
Chuanxiao Dong 2017-06-26 15:20:50 +08:00 committed by Zhenyu Wang
parent 62d02fd1f8
commit f16bd3dda2
1 changed files with 9 additions and 5 deletions
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14
drivers/gpu/drm/i915/gvt/kvmgt.c
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@ -260,16 +260,20 @@ 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,