[PATCH 0/2] vhost: Add support to indirect descriptors on Rx path

[PATCH 0/2] vhost: Add support to indirect descriptors on Rx path

[Maxime Coquelin]

Indirect descriptor feature has been enabled in v16.11-rc1, but only TX path
was implemented.
However, some configurations expect it is supported for the Rx path:
 - Windows guests with and without mergeable buffers enabled
 - Linux guests with Kernel drivr with mergeable buffers disabled

This series add the support of indirect descs for the Rx path, and has been
tested with following configurations:
 - Windows guest with indirect ON, mergeeable ON/OFF
 - Linux guest with Kernel driver with indirect ON/OFF, mergeable ON/OFF
 - Linux guest with Virtio PMD with mergeable ON/OFF

The performance degradation measured with/without this series with Virtio PMD
is around 1% (which doesn't use indirect descs for the Rx path).

The series is based on top of "vhost: optimize mergeable Rx path" v7.

Maxime Coquelin (2):
  vhost: Add indirect desc support to Rx mergeable path
  vhost: Add indirect desc support to the Rx no-mergeable path

 lib/librte_vhost/virtio_net.c | 73 ++++++++++++++++++++++++++++++-------------
 1 file changed, 51 insertions(+), 22 deletions(-)

-- 
2.7.4

[PATCH 1/2] vhost: Add indirect desc support to Rx mergeable path

[Maxime Coquelin]

Windows virtio-net driver uses indirect descriptors with
mergeable buffers.

This patch adds its support, fixing the use of indirect
descriptors with these guests.

Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Zhihong Wang <zhihong.wang@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/virtio_net.c | 43 ++++++++++++++++++++++++++++---------------
 1 file changed, 28 insertions(+), 15 deletions(-)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index b784dba..0941186 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -351,29 +351,41 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 }
 
 static inline int __attribute__((always_inline))
-fill_vec_buf(struct vhost_virtqueue *vq, uint32_t avail_idx,
-	     uint32_t *vec_idx, struct buf_vector *buf_vec,
-	     uint16_t *desc_chain_head, uint16_t *desc_chain_len)
+fill_vec_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
+			 uint32_t avail_idx, uint32_t *vec_idx,
+			 struct buf_vector *buf_vec, uint16_t *desc_chain_head,
+			 uint16_t *desc_chain_len)
 {
 	uint16_t idx = vq->avail->ring[avail_idx & (vq->size - 1)];
 	uint32_t vec_id = *vec_idx;
 	uint32_t len    = 0;
+	struct vring_desc *descs = vq->desc;
 
 	*desc_chain_head = idx;
+
+	if (vq->desc[idx].flags & VRING_DESC_F_INDIRECT) {
+		descs = (struct vring_desc *)(uintptr_t)
+					gpa_to_vva(dev, vq->desc[idx].addr);
+		if (unlikely(!descs))
+			return -1;
+
+		idx = 0;
+	}
+
 	while (1) {
 		if (unlikely(vec_id >= BUF_VECTOR_MAX || idx >= vq->size))
 			return -1;
 
-		len += vq->desc[idx].len;
-		buf_vec[vec_id].buf_addr = vq->desc[idx].addr;
-		buf_vec[vec_id].buf_len  = vq->desc[idx].len;
+		len += descs[idx].len;
+		buf_vec[vec_id].buf_addr = descs[idx].addr;
+		buf_vec[vec_id].buf_len  = descs[idx].len;
 		buf_vec[vec_id].desc_idx = idx;
 		vec_id++;
 
-		if ((vq->desc[idx].flags & VRING_DESC_F_NEXT) == 0)
+		if ((descs[idx].flags & VRING_DESC_F_NEXT) == 0)
 			break;
 
-		idx = vq->desc[idx].next;
+		idx = descs[idx].next;
 	}
 
 	*desc_chain_len = len;
@@ -386,9 +398,9 @@ fill_vec_buf(struct vhost_virtqueue *vq, uint32_t avail_idx,
  * Returns -1 on fail, 0 on success
  */
 static inline int
-reserve_avail_buf_mergeable(struct vhost_virtqueue *vq, uint32_t size,
-			    struct buf_vector *buf_vec, uint16_t *num_buffers,
-			    uint16_t avail_head)
+reserve_avail_buf_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
+				uint32_t size, struct buf_vector *buf_vec,
+				uint16_t *num_buffers, uint16_t avail_head)
 {
 	uint16_t cur_idx;
 	uint32_t vec_idx = 0;
@@ -404,8 +416,8 @@ reserve_avail_buf_mergeable(struct vhost_virtqueue *vq, uint32_t size,
 		if (unlikely(cur_idx == avail_head))
 			return -1;
 
-		if (unlikely(fill_vec_buf(vq, cur_idx, &vec_idx, buf_vec,
-					  &head_idx, &len) < 0))
+		if (unlikely(fill_vec_buf(dev, vq, cur_idx, &vec_idx, buf_vec,
+						&head_idx, &len) < 0))
 			return -1;
 		len = RTE_MIN(len, size);
 		update_shadow_used_ring(vq, head_idx, len);
@@ -546,8 +558,9 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 	for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
 		uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
 
-		if (unlikely(reserve_avail_buf_mergeable(vq, pkt_len, buf_vec,
-					&num_buffers, avail_head) < 0)) {
+		if (unlikely(reserve_avail_buf_mergeable(dev, vq,
+						pkt_len, buf_vec, &num_buffers,
+						avail_head) < 0)) {
 			LOG_DEBUG(VHOST_DATA,
 				"(%d) failed to get enough desc from vring\n",
 				dev->vid);
-- 
2.7.4

[PATCH 2/2] vhost: Add indirect desc support to the Rx no-mergeable path

[Maxime Coquelin]

Linux virtio-net kernel driver uses indirect descriptors when
mergeable buffers are not used.

This patch adds its support, fixing the use of indirect
descriptors with these guests.

Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Ciara Loftus <ciara.loftus@intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/virtio_net.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 0941186..8365894 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -186,8 +186,8 @@ copy_virtio_net_hdr(struct virtio_net *dev, uint64_t desc_addr,
 }
 
 static inline int __attribute__((always_inline))
-copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
-		  struct rte_mbuf *m, uint16_t desc_idx)
+copy_mbuf_to_desc(struct virtio_net *dev, struct vring_desc *descs,
+		  struct rte_mbuf *m, uint16_t desc_idx, uint32_t size)
 {
 	uint32_t desc_avail, desc_offset;
 	uint32_t mbuf_avail, mbuf_offset;
@@ -196,7 +196,7 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	uint64_t desc_addr;
 	struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0};
 
-	desc = &vq->desc[desc_idx];
+	desc = &descs[desc_idx];
 	desc_addr = gpa_to_vva(dev, desc->addr);
 	/*
 	 * Checking of 'desc_addr' placed outside of 'unlikely' macro to avoid
@@ -233,10 +233,10 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 				/* Room in vring buffer is not enough */
 				return -1;
 			}
-			if (unlikely(desc->next >= vq->size))
+			if (unlikely(desc->next >= size))
 				return -1;
 
-			desc = &vq->desc[desc->next];
+			desc = &descs[desc->next];
 			desc_addr = gpa_to_vva(dev, desc->addr);
 			if (unlikely(!desc_addr))
 				return -1;
@@ -276,8 +276,9 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 	struct vhost_virtqueue *vq;
 	uint16_t avail_idx, free_entries, start_idx;
 	uint16_t desc_indexes[MAX_PKT_BURST];
+	struct vring_desc *descs;
 	uint16_t used_idx;
-	uint32_t i;
+	uint32_t i, sz;
 
 	LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
 	if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->virt_qp_nb))) {
@@ -319,7 +320,22 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 		uint16_t desc_idx = desc_indexes[i];
 		int err;
 
-		err = copy_mbuf_to_desc(dev, vq, pkts[i], desc_idx);
+		if (vq->desc[desc_idx].flags & VRING_DESC_F_INDIRECT) {
+			descs = (struct vring_desc *)(uintptr_t)gpa_to_vva(dev,
+					vq->desc[desc_idx].addr);
+			if (unlikely(!descs)) {
+				count = i;
+				break;
+			}
+
+			desc_idx = 0;
+			sz = vq->desc[desc_idx].len / sizeof(*descs);
+		} else {
+			descs = vq->desc;
+			sz = vq->size;
+		}
+
+		err = copy_mbuf_to_desc(dev, descs, pkts[i], desc_idx, sz);
 		if (unlikely(err)) {
 			used_idx = (start_idx + i) & (vq->size - 1);
 			vq->used->ring[used_idx].len = dev->vhost_hlen;
-- 
2.7.4

Re: [PATCH 0/2] vhost: Add support to indirect descriptors on Rx path

[Yuanhan Liu]

On Tue, Oct 18, 2016 at 05:35:37PM +0200, Maxime Coquelin wrote:
> Indirect descriptor feature has been enabled in v16.11-rc1, but only TX path
> was implemented.
> However, some configurations expect it is supported for the Rx path:
>  - Windows guests with and without mergeable buffers enabled
>  - Linux guests with Kernel drivr with mergeable buffers disabled
> 
> This series add the support of indirect descs for the Rx path, and has been
> tested with following configurations:
>  - Windows guest with indirect ON, mergeeable ON/OFF
>  - Linux guest with Kernel driver with indirect ON/OFF, mergeable ON/OFF
>  - Linux guest with Virtio PMD with mergeable ON/OFF
> 
> The performance degradation measured with/without this series with Virtio PMD
> is around 1% (which doesn't use indirect descs for the Rx path).
> 
> The series is based on top of "vhost: optimize mergeable Rx path" v7.

Series applied to dpdk-next-virtio.

Thanks.

	--yliu
> 
> Maxime Coquelin (2):
>   vhost: Add indirect desc support to Rx mergeable path
>   vhost: Add indirect desc support to the Rx no-mergeable path
> 
>  lib/librte_vhost/virtio_net.c | 73 ++++++++++++++++++++++++++++++-------------
>  1 file changed, 51 insertions(+), 22 deletions(-)
> 
> -- 
> 2.7.4