Re: [PATCH v3 2/5] vhost: prepare async for descriptor to mbuf refactoring

[Maxime Coquelin]

On 4/19/22 05:43, xuan.d...@intel.com wrote:

From: Xuan Ding <xuan.d...@intel.com>

This patch refactors vhost async enqueue path and dequeue path to use
the same function async_fill_seg() for preparing batch elements,
which simplifies the code without performance degradation.

Signed-off-by: Xuan Ding <xuan.d...@intel.com>
---
  lib/vhost/virtio_net.c | 23 +++++++++++++++--------
  1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 6d53016c75..391fb82f0e 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -997,13 +997,14 @@ async_iter_reset(struct vhost_async *async)
  }

static __rte_always_inline int

-async_mbuf_to_desc_seg(struct virtio_net *dev, struct vhost_virtqueue *vq,
+async_fill_seg(struct virtio_net *dev, struct vhost_virtqueue *vq,
                struct rte_mbuf *m, uint32_t mbuf_offset,
-               uint64_t buf_iova, uint32_t cpy_len)
+               uint64_t buf_iova, uint32_t cpy_len, bool to_desc)
  {
        struct vhost_async *async = vq->async;
        uint64_t mapped_len;
        uint32_t buf_offset = 0;
+       void *src, *dst;
        void *host_iova;

while (cpy_len) {

@@ -1015,10 +1016,16 @@ async_mbuf_to_desc_seg(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
                        return -1;
                }

- if (unlikely(async_iter_add_iovec(dev, async,

-                                               (void 
*)(uintptr_t)rte_pktmbuf_iova_offset(m,
-                                                       mbuf_offset),
-                                               host_iova, (size_t)mapped_len)))
+               if (to_desc) {
+                       src = (void *)(uintptr_t)rte_pktmbuf_iova_offset(m, 
mbuf_offset);
+                       dst = host_iova;
+               } else {
+                       src = host_iova;
+                       dst = (void *)(uintptr_t)rte_pktmbuf_iova_offset(m, 
mbuf_offset);
+               }
+
+               if (unlikely(async_iter_add_iovec(dev, async, src, dst,
+                                                (size_t)mapped_len)))

Minor, but it may fit in a single line.

                        return -1;

cpy_len -= (uint32_t)mapped_len;

@@ -1167,8 +1174,8 @@ mbuf_to_desc(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
                cpy_len = RTE_MIN(buf_avail, mbuf_avail);

if (is_async) {

-                       if (async_mbuf_to_desc_seg(dev, vq, m, mbuf_offset,
-                                               buf_iova + buf_offset, cpy_len) 
< 0)
+                       if (async_fill_seg(dev, vq, m, mbuf_offset,
+                                               buf_iova + buf_offset, cpy_len, 
true) < 0)
                                goto error;
                } else {
                        sync_fill_seg(dev, vq, m, mbuf_offset,

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

Thanks,
Maxime