diff mbox series

[v3] vhost: fix packed ring descriptor update in async enqueue

Message ID 20211116151756.2420165-1-jiayu.hu@intel.com (mailing list archive)
State Accepted, archived
Delegated to: Maxime Coquelin
Headers
Series [v3] vhost: fix packed ring descriptor update in async enqueue |

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation success Compilation OK
ci/github-robot: build success github build: passed
ci/intel-Testing success Testing PASS
ci/iol-mellanox-Performance success Performance Testing PASS
ci/iol-broadcom-Performance success Performance Testing PASS
ci/iol-broadcom-Functional success Functional Testing PASS
ci/iol-x86_64-unit-testing success Testing PASS
ci/iol-aarch64-compile-testing success Testing PASS
ci/iol-aarch64-unit-testing success Testing PASS
ci/iol-x86_64-compile-testing success Testing PASS
ci/iol-intel-Functional success Functional Testing PASS
ci/iol-intel-Performance success Performance Testing PASS

Commit Message

Hu, Jiayu Nov. 16, 2021, 3:17 p.m. UTC 
  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 <jiayu.hu@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
---
v3:
* fix typo
v2:
* update commit log
---
 lib/vhost/virtio_net.c | 122 ++++++++++++++++++-----------------------
 1 file changed, 54 insertions(+), 68 deletions(-)

Comments

Maxime Coquelin Nov. 16, 2021, 9:59 a.m. UTC | #1 
On 11/16/21 16:17, Jiayu Hu wrote:
> 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 <jiayu.hu@intel.com>
> Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
> ---
> v3:
> * fix typo
> v2:
> * update commit log
> ---
>   lib/vhost/virtio_net.c | 122 ++++++++++++++++++-----------------------
>   1 file changed, 54 insertions(+), 68 deletions(-)
> 

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime
Maxime Coquelin Nov. 16, 2021, 10:25 a.m. UTC | #2 
On 11/16/21 16:17, Jiayu Hu wrote:
> 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 <jiayu.hu@intel.com>
> Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
> ---
> v3:
> * fix typo
> v2:
> * update commit log
> ---
>   lib/vhost/virtio_net.c | 122 ++++++++++++++++++-----------------------
>   1 file changed, 54 insertions(+), 68 deletions(-)
> 

Applied to dpdk-next-virtio/main.

Thanks,
Maxime
diff mbox series

Patch

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