Re: [PATCH v2 10/10] net/virtio: fix multiple queue enabling

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Sat, Nov 05, 2016 at 05:41:05PM +0800, Yuanhan Liu wrote:
> When queue number shrinks to 1 from X, the following code stops us
> sending the multiple queue ctrl message:
> 
>         if (nb_queues > 1) {
>                 if (virtio_set_multiple_queues(dev, nb_queues) != 0)
>                         return -EINVAL;
>         }
> 
> This ends up with still X queues being enabled, which is obviously
> wrong. Fix it by removing the check.
> 
> Fixes: 823ad647950a ("virtio: support multiple queues")
> 
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

This breaks the virtio-user case, where ctrl-queue is not enabled by
defeault.

Here is an update patch would fix this.

	--yliu

---
>From 22502943764a99b1398d40f0110f8ce28323323a Mon Sep 17 00:00:00 2001
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Date: Sat, 5 Nov 2016 16:53:27 +0800
Subject: [PATCH v3 10/10] net/virtio: fix multiple queue enabling

When queue number shrinks to 1 from X, the following code stops us
sending the multiple queue ctrl message:

        if (nb_queues > 1) {
                if (virtio_set_multiple_queues(dev, nb_queues) != 0)
                        return -EINVAL;
        }

This ends up with still X queues being enabled, which is obviously
wrong. Fix it by replacing the check with a multiple queue enabled
or not check.

Fixes: 823ad647950a ("virtio: support multiple queues")

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---
v3: - fix the virtio-user case, which is default with ctrl-queue
      being disabled. Thus virtio_set_multiple_queues fails.
---
 drivers/net/virtio/virtio_ethdev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
index d70bd00..18da98f 100644
--- a/drivers/net/virtio/virtio_ethdev.c
+++ b/drivers/net/virtio/virtio_ethdev.c
@@ -1472,6 +1472,7 @@ virtio_dev_start(struct rte_eth_dev *dev)
 	uint16_t nb_queues, i;
 	struct virtnet_rx *rxvq;
 	struct virtnet_tx *txvq __rte_unused;
+	struct virtio_hw *hw = dev->data->dev_private;
 
 	/* check if lsc interrupt feature is enabled */
 	if (dev->data->dev_conf.intr_conf.lsc) {
@@ -1494,7 +1495,7 @@ virtio_dev_start(struct rte_eth_dev *dev)
 	 *vhost backend will have no chance to be waked up
 	 */
 	nb_queues = RTE_MAX(dev->data->nb_rx_queues, dev->data->nb_tx_queues);
-	if (nb_queues > 1) {
+	if (hw->max_queue_pairs > 1) {
 		if (virtio_set_multiple_queues(dev, nb_queues) != 0)
 			return -EINVAL;
 	}
-- 
1.9.0