Re: [PATCH V2 9/9] vhost: do not return -EAGIAN for non blocking invalidation too early

On 2019/7/31 下午5:59, Stefano Garzarella wrote:

A little typo in the title: s/EAGIAN/EAGAIN

Thanks,
Stefano

Right, will fix if need respin or Michael can help to fix.

Thanks

On Wed, Jul 31, 2019 at 04:46:55AM -0400, Jason Wang wrote:

quoted

Instead of returning -EAGAIN unconditionally, we'd better do that only
we're sure the range is overlapped with the metadata area.

Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address")
Signed-off-by: Jason Wang <redacted>
---
  drivers/vhost/vhost.c | 32 +++++++++++++++++++-------------
  1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index fc2da8a0c671..96c6aeb1871f 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c

@@ -399,16 +399,19 @@ static void inline vhost_vq_sync_access(struct vhost_virtqueue *vq)
  	smp_mb();
  }
  
-static void vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
-				      int index,
-				      unsigned long start,
-				      unsigned long end)
+static int vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
+				     int index,
+				     unsigned long start,
+				     unsigned long end,
+				     bool blockable)
  {
  	struct vhost_uaddr *uaddr = &vq->uaddrs[index];
  	struct vhost_map *map;
  
  	if (!vhost_map_range_overlap(uaddr, start, end))
-		return;
+		return 0;
+	else if (!blockable)
+		return -EAGAIN;
  
  	spin_lock(&vq->mmu_lock);
  	++vq->invalidate_count;

@@ -423,6 +426,8 @@ static void vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
  		vhost_set_map_dirty(vq, map, index);
  		vhost_map_unprefetch(map);
  	}
+
+	return 0;
  }
  
  static void vhost_invalidate_vq_end(struct vhost_virtqueue *vq,

@@ -443,18 +448,19 @@ static int vhost_invalidate_range_start(struct mmu_notifier *mn,
  {
  	struct vhost_dev *dev = container_of(mn, struct vhost_dev,
  					     mmu_notifier);
-	int i, j;
-
-	if (!mmu_notifier_range_blockable(range))
-		return -EAGAIN;
+	bool blockable = mmu_notifier_range_blockable(range);
+	int i, j, ret;
  
  	for (i = 0; i < dev->nvqs; i++) {
  		struct vhost_virtqueue *vq = dev->vqs[i];
  
-		for (j = 0; j < VHOST_NUM_ADDRS; j++)
-			vhost_invalidate_vq_start(vq, j,
-						  range->start,
-						  range->end);
+		for (j = 0; j < VHOST_NUM_ADDRS; j++) {
+			ret = vhost_invalidate_vq_start(vq, j,
+							range->start,
+							range->end, blockable);
+			if (ret)
+				return ret;
+		}
  	}
  
  	return 0;

-- 
2.18.1