On Tue, 30 Jul 2024 18:20:20 -0700, Jakub Kicinski [off-list ref] wrote:

On Mon, 29 Jul 2024 20:47:55 +0800 Heng Qi wrote:

quoted

Subject: [PATCH net] virtio_net: Avoid sending unnecessary vq coalescing commands

subject currently reads like this is an optimization, could you
rephrase?

Jason's rephrase will be used.

quoted

From the virtio spec:

	The driver MUST have negotiated the VIRTIO_NET_F_VQ_NOTF_COAL
	feature when issuing commands VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET
	and VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET.

The driver must not send vq notification coalescing commands if
VIRTIO_NET_F_VQ_NOTF_COAL is not negotiated. This limitation of course
applies to vq resize.

Fixes: f61fe5f081cf ("virtio-net: fix the vq coalescing setting for vq resize")
Signed-off-by: Heng Qi <redacted>
---
 drivers/net/virtio_net.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0383a3e136d6..eb115e807882 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -3708,6 +3708,7 @@ static int virtnet_set_ringparam(struct net_device *dev,
 	u32 rx_pending, tx_pending;
 	struct receive_queue *rq;
 	struct send_queue *sq;
+	u32 pkts, usecs;
 	int i, err;
 
 	if (ring->rx_mini_pending || ring->rx_jumbo_pending)

@@ -3740,11 +3741,13 @@ static int virtnet_set_ringparam(struct net_device *dev,
 			 * through the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command, or, if the driver
 			 * did not set any TX coalescing parameters, to 0.
 			 */
-			err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, i,
-							       vi->intr_coal_tx.max_usecs,
-							       vi->intr_coal_tx.max_packets);
-			if (err)
-				return err;
+			if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) {
+				usecs = vi->intr_coal_tx.max_usecs;
+				pkts = vi->intr_coal_tx.max_packets;
+				err = virtnet_send_tx_ctrl_coal_vq_cmd(vi, i, usecs, pkts);
+				if (err)
+					return err;

Can you check the feature inside the
virtnet_send_.x_ctrl_coal_vq_cmd() helpers?
5 levels of indentation is a bit much

Makes sense. Will update in the next version.

Thanks.

-- 
pw-bot: cr