[dpdk-stable] patch 'net/virtio: fix vectorized Rx queue rearm' has been queued to stable release 20.11.2

[Xueming Li]

Hi,

FYI, your patch has been queued to stable release 20.11.2

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 06/14/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/steevenlee/dpdk

This queued commit can be viewed at:
https://github.com/steevenlee/dpdk/commit/96c209b1a6b0bdce7875fb91e8db27e0d930fc91

Thanks.

Xueming Li <xuemingl at nvidia.com>

---
>From 96c209b1a6b0bdce7875fb91e8db27e0d930fc91 Mon Sep 17 00:00:00 2001
From: Xueming Li <xuemingl at nvidia.com>
Date: Wed, 14 Apr 2021 22:14:04 +0800
Subject: [PATCH] net/virtio: fix vectorized Rx queue rearm
Cc: Luca Boccassi <bluca at debian.org>

[ upstream commit d99088431ea5d6bb568c5cb5542688453084dcc6 ]

When Rx queue worked in vectorized mode and rxd <= 512, under traffic of
high PPS rate, testpmd often start and receive packets of rxd without
further growth.

Testpmd started with rxq flush which tried to rx MAX_PKT_BURST(512)
packets and drop. When Rx burst size >= Rx queue size, all descriptors
in used queue consumed without rearm, device can't receive more packets.
The next Rx burst returned at once since no used descriptors found,
rearm logic was skipped, rx vq kept in starving state.

To avoid rx vq starving, this patch always check the available queue,
rearm if needed even no used descriptor reported by device.

Fixes: fc3d66212fed ("virtio: add vector Rx")
Fixes: 2d7c37194ee4 ("net/virtio: add NEON based Rx handler")
Fixes: 52b5a707e6ca ("net/virtio: add Altivec Rx")

Signed-off-by: Xueming Li <xuemingl at nvidia.com>
Reviewed-by: David Christensen <drc at linux.vnet.ibm.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
---
 drivers/net/virtio/virtio_rxtx_simple_altivec.c | 12 ++++++------
 drivers/net/virtio/virtio_rxtx_simple_neon.c    | 12 ++++++------
 drivers/net/virtio/virtio_rxtx_simple_sse.c     | 12 ++++++------
 3 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/net/virtio/virtio_rxtx_simple_altivec.c b/drivers/net/virtio/virtio_rxtx_simple_altivec.c
index a260ebdf57..bcd7d5ee59 100644
--- a/drivers/net/virtio/virtio_rxtx_simple_altivec.c
+++ b/drivers/net/virtio/virtio_rxtx_simple_altivec.c
@@ -85,6 +85,12 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
 	if (unlikely(nb_pkts < RTE_VIRTIO_DESC_PER_LOOP))
 		return 0;
 
+	if (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {
+		virtio_rxq_rearm_vec(rxvq);
+		if (unlikely(virtqueue_kick_prepare(vq)))
+			virtqueue_notify(vq);
+	}
+
 	nb_used = virtqueue_nused(vq);
 
 	rte_compiler_barrier();
@@ -102,12 +108,6 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
 
 	rte_prefetch0(rused);
 
-	if (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {
-		virtio_rxq_rearm_vec(rxvq);
-		if (unlikely(virtqueue_kick_prepare(vq)))
-			virtqueue_notify(vq);
-	}
-
 	nb_total = nb_used;
 	ref_rx_pkts = rx_pkts;
 	for (nb_pkts_received = 0;
diff --git a/drivers/net/virtio/virtio_rxtx_simple_neon.c b/drivers/net/virtio/virtio_rxtx_simple_neon.c
index 12e034dc0a..afe6a25944 100644
--- a/drivers/net/virtio/virtio_rxtx_simple_neon.c
+++ b/drivers/net/virtio/virtio_rxtx_simple_neon.c
@@ -84,6 +84,12 @@ virtio_recv_pkts_vec(void *rx_queue,
 	if (unlikely(nb_pkts < RTE_VIRTIO_DESC_PER_LOOP))
 		return 0;
 
+	if (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {
+		virtio_rxq_rearm_vec(rxvq);
+		if (unlikely(virtqueue_kick_prepare(vq)))
+			virtqueue_notify(vq);
+	}
+
 	/* virtqueue_nused has a load-acquire or rte_io_rmb inside */
 	nb_used = virtqueue_nused(vq);
 
@@ -100,12 +106,6 @@ virtio_recv_pkts_vec(void *rx_queue,
 
 	rte_prefetch_non_temporal(rused);
 
-	if (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {
-		virtio_rxq_rearm_vec(rxvq);
-		if (unlikely(virtqueue_kick_prepare(vq)))
-			virtqueue_notify(vq);
-	}
-
 	nb_total = nb_used;
 	ref_rx_pkts = rx_pkts;
 	for (nb_pkts_received = 0;
diff --git a/drivers/net/virtio/virtio_rxtx_simple_sse.c b/drivers/net/virtio/virtio_rxtx_simple_sse.c
index 1056e9c20b..e4e85c2b80 100644
--- a/drivers/net/virtio/virtio_rxtx_simple_sse.c
+++ b/drivers/net/virtio/virtio_rxtx_simple_sse.c
@@ -85,6 +85,12 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
 	if (unlikely(nb_pkts < RTE_VIRTIO_DESC_PER_LOOP))
 		return 0;
 
+	if (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {
+		virtio_rxq_rearm_vec(rxvq);
+		if (unlikely(virtqueue_kick_prepare(vq)))
+			virtqueue_notify(vq);
+	}
+
 	nb_used = virtqueue_nused(vq);
 
 	if (unlikely(nb_used == 0))
@@ -100,12 +106,6 @@ virtio_recv_pkts_vec(void *rx_queue, struct rte_mbuf **rx_pkts,
 
 	rte_prefetch0(rused);
 
-	if (vq->vq_free_cnt >= RTE_VIRTIO_VPMD_RX_REARM_THRESH) {
-		virtio_rxq_rearm_vec(rxvq);
-		if (unlikely(virtqueue_kick_prepare(vq)))
-			virtqueue_notify(vq);
-	}
-
 	nb_total = nb_used;
 	ref_rx_pkts = rx_pkts;
 	for (nb_pkts_received = 0;
-- 
2.25.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-06-12 06:53:58.447683600 +0800
+++ 0071-net-virtio-fix-vectorized-Rx-queue-rearm.patch	2021-06-12 06:53:56.330000000 +0800
@@ -1 +1 @@
-From d99088431ea5d6bb568c5cb5542688453084dcc6 Mon Sep 17 00:00:00 2001
+From 96c209b1a6b0bdce7875fb91e8db27e0d930fc91 Mon Sep 17 00:00:00 2001
@@ -4,0 +5,3 @@
+Cc: Luca Boccassi <bluca at debian.org>
+
+[ upstream commit d99088431ea5d6bb568c5cb5542688453084dcc6 ]
@@ -22 +24,0 @@
-Cc: stable at dpdk.org
@@ -34 +36 @@
-index 62e5100a48..7534974ef4 100644
+index a260ebdf57..bcd7d5ee59 100644
@@ -64 +66 @@
-index c8e4b13a02..7fd92d1b0c 100644
+index 12e034dc0a..afe6a25944 100644
@@ -94 +96 @@
-index ff4eba33d6..7577f5e86d 100644
+index 1056e9c20b..e4e85c2b80 100644