From af4d7ad5d90baf21e99d0ab91058fcdf8ae90f96 Mon Sep 17 00:00:00 2001 From: Jiayu Hu Date: Tue, 16 Nov 2021 10:17:56 -0500 Subject: [PATCH] vhost: fix packed ring descriptor update in async enqueue 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 Reviewed-by: Chenbo Xia Reviewed-by: Maxime Coquelin --- 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