vhost: fix overflow of avail entries count

Virtio 1.0 says that the effective capacity of vrings
is equal to the virtqueue size. When avail ring was full,
we detected it as empty.

Change-Id: I72f5d45cdc14db6b934ce7780e603a3de3131594
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/396804
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Pawel Wodkowski <pawelx.wodkowski@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
This commit is contained in:
Dariusz Stojaczyk 2018-01-28 10:53:03 +01:00 committed by Jim Harris
parent a78c896369
commit 808a2b05c2

View File

@ -102,13 +102,21 @@ spdk_vhost_vq_avail_ring_get(struct spdk_vhost_virtqueue *virtqueue, uint16_t *r
struct vring_avail *avail = vring->avail;
uint16_t size_mask = vring->size - 1;
uint16_t last_idx = vring->last_avail_idx, avail_idx = avail->idx;
uint16_t count = RTE_MIN((avail_idx - last_idx) & size_mask, reqs_len);
uint16_t i;
uint16_t count, i;
count = avail_idx - last_idx;
if (spdk_likely(count == 0)) {
return 0;
}
if (spdk_unlikely(count > vring->size)) {
/* TODO: the queue is unrecoverably broken and should be marked so.
* For now we will fail silently and report there are no new avail entries.
*/
return 0;
}
count = spdk_min(count, reqs_len);
vring->last_avail_idx += count;
for (i = 0; i < count; i++) {
reqs[i] = vring->avail->ring[(last_idx + i) & size_mask];