[PATCH V5 9/9] vhost: do not return -EAGAIN for non blocking invalidation too early

Jason Wang
2019-08-09T05:49:40Z

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 <jasowang@redhat.com>
---
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 d8863aaaf0f6..f98155f28f02 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -371,16 +371,19 @@ static void inline vhost_vq_access_map_end(struct vhost_virtqueue *vq)
spin_unlock(&vq->mmu_lock);
}

-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;
@@ -394,6 +397,8 @@ 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,
@@ -414,18 +419,19 @@ 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