If the packet uses multiple descriptors and its descriptor indices are
wrapped, the first descriptor flag is not updated last, which may cause
virtio read the incomplete packet. For example, given a packet uses 64
descriptors, and virtio ring size is 256, and its descriptor indices are
224~255 and 0~31, current implementation will update 224~255 descriptor
flags earlier than 0~31 descriptor flags.
This patch fixes this issue by updating descriptor flags in one loop,
so that the first descriptor flag is always updated last.
Fixes: 873e8dad6f49 ("vhost: support packed ring in async datapath")
Signed-off-by: Jiayu Hu <[email protected]>
Reviewed-by: Chenbo Xia <[email protected]>
---
v3:
* fix typo
v2:
* update commit log
---
lib/vhost/virtio_net.c | 122 ++++++++++++++++++-----------------------
1 file changed, 54 insertions(+), 68 deletions(-)
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index cef4bcf15c..b3d954aab4 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -1549,60 +1549,6 @@ virtio_dev_rx_async_submit_split(struct virtio_net *dev,
return pkt_idx;
}
-static __rte_always_inline void
-vhost_update_used_packed(struct vhost_virtqueue *vq,
- struct vring_used_elem_packed *shadow_ring,
- uint16_t count)
-{
- int i;
- uint16_t used_idx = vq->last_used_idx;
- uint16_t head_idx = vq->last_used_idx;
- uint16_t head_flags = 0;
-
- if (count == 0)
- return;
-
- /* Split loop in two to save memory barriers */
- for (i = 0; i < count; i++) {
- vq->desc_packed[used_idx].id = shadow_ring[i].id;
- vq->desc_packed[used_idx].len = shadow_ring[i].len;
-
- used_idx += shadow_ring[i].count;
- if (used_idx >= vq->size)
- used_idx -= vq->size;
- }
-
- /* The ordering for storing desc flags needs to be enforced. */
- rte_atomic_thread_fence(__ATOMIC_RELEASE);
-
- for (i = 0; i < count; i++) {
- uint16_t flags;
-
- if (vq->shadow_used_packed[i].len)
- flags = VRING_DESC_F_WRITE;
- else
- flags = 0;
-
- if (vq->used_wrap_counter) {
- flags |= VRING_DESC_F_USED;
- flags |= VRING_DESC_F_AVAIL;
- } else {
- flags &= ~VRING_DESC_F_USED;
- flags &= ~VRING_DESC_F_AVAIL;
- }
-
- if (i > 0) {
- vq->desc_packed[vq->last_used_idx].flags = flags;
- } else {
- head_idx = vq->last_used_idx;
- head_flags = flags;
- }
-
- vq_inc_last_used_packed(vq, shadow_ring[i].count);
- }
-
- vq->desc_packed[head_idx].flags = head_flags;
-}
static __rte_always_inline int
vhost_enqueue_async_packed(struct virtio_net *dev,
@@ -1819,23 +1765,63 @@ write_back_completed_descs_packed(struct
vhost_virtqueue *vq,
uint16_t n_buffers)
{
struct vhost_async *async = vq->async;
- uint16_t nr_left = n_buffers;
- uint16_t from, to;
+ uint16_t from = async->last_buffer_idx_packed;
+ uint16_t used_idx = vq->last_used_idx;
+ uint16_t head_idx = vq->last_used_idx;
+ uint16_t head_flags = 0;
+ uint16_t i;
- do {
- from = async->last_buffer_idx_packed;
- to = (from + nr_left) % vq->size;
- if (to > from) {
- vhost_update_used_packed(vq, async->buffers_packed +
from, to - from);
- async->last_buffer_idx_packed += nr_left;
- nr_left = 0;
+ /* Split loop in two to save memory barriers */
+ for (i = 0; i < n_buffers; i++) {
+ vq->desc_packed[used_idx].id = async->buffers_packed[from].id;
+ vq->desc_packed[used_idx].len = async->buffers_packed[from].len;
+
+ used_idx += async->buffers_packed[from].count;
+ if (used_idx >= vq->size)
+ used_idx -= vq->size;
+
+ from++;
+ if (from >= vq->size)
+ from = 0;
+ }
+
+ /* The ordering for storing desc flags needs to be enforced. */
+ rte_atomic_thread_fence(__ATOMIC_RELEASE);
+
+ from = async->last_buffer_idx_packed;
+
+ for (i = 0; i < n_buffers; i++) {
+ uint16_t flags;
+
+ if (async->buffers_packed[from].len)
+ flags = VRING_DESC_F_WRITE;
+ else
+ flags = 0;
+
+ if (vq->used_wrap_counter) {
+ flags |= VRING_DESC_F_USED;
+ flags |= VRING_DESC_F_AVAIL;
} else {
- vhost_update_used_packed(vq, async->buffers_packed +
from,
- vq->size - from);
- async->last_buffer_idx_packed = 0;
- nr_left -= vq->size - from;
+ flags &= ~VRING_DESC_F_USED;
+ flags &= ~VRING_DESC_F_AVAIL;
}
- } while (nr_left > 0);
+
+ if (i > 0) {
+ vq->desc_packed[vq->last_used_idx].flags = flags;
+ } else {
+ head_idx = vq->last_used_idx;
+ head_flags = flags;
+ }
+
+ vq_inc_last_used_packed(vq, async->buffers_packed[from].count);
+
+ from++;
+ if (from == vq->size)
+ from = 0;
+ }
+
+ vq->desc_packed[head_idx].flags = head_flags;
+ async->last_buffer_idx_packed = from;
}
static __rte_always_inline uint16_t
--
2.25.1
