[PATCH net 1/6] virtio-net: initially change the value of tx-frames
From: Heng Qi <hidden>
Date: 2023-09-19 07:49:23
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
Background:
1. Commit 0c465be183c7 ("virtio_net: ethtool tx napi configuration") uses
tx-frames to toggle napi_tx (0 off and 1 on) if notification coalescing
is not supported.
2. Commit 31c03aef9bc2 ("virtio_net: enable napi_tx by default") enables
napi_tx for all txqs by default.
Status:
When virtio-net supports notification coalescing, after initialization,
tx-frames is 0 and napi_tx is true.
Problem:
When the user only wants to set rx coalescing params using
ethtool -C eth0 rx-usecs 10, or
ethtool -Q eth0 queue_mask 0x1 -C rx-usecs 10,
these cmds will carry tx-frames as 0, causing the napi_tx switching condition
is satisfied. Then the user gets:
netlink error: Device or resource busy.
The same happens when trying to set rx-frames, adaptive_rx, adaptive_tx...
Result:
When notification coalescing feature is negotiated, initially make the
value of tx-frames to be consistent with napi_tx.
For compatibility with the past, it is still supported to use tx-frames
to toggle napi_tx.
Reported-by: Xiaoming Zhao <redacted>
Signed-off-by: Heng Qi <redacted>
---
drivers/net/virtio_net.c | 42 +++++++++++++++++++++++++++++++++-------
1 file changed, 35 insertions(+), 7 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fe7f314d65c9..fd5bc8d59eda 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -4442,13 +4442,6 @@ static int virtnet_probe(struct virtio_device *vdev) dev->xdp_features |= NETDEV_XDP_ACT_RX_SG; } - if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) { - vi->intr_coal_rx.max_usecs = 0; - vi->intr_coal_tx.max_usecs = 0; - vi->intr_coal_tx.max_packets = 0; - vi->intr_coal_rx.max_packets = 0; - } - if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT)) vi->has_rss_hash_report = true;
@@ -4523,6 +4516,41 @@ static int virtnet_probe(struct virtio_device *vdev) if (err) goto free; + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_NOTF_COAL)) { + vi->intr_coal_rx.max_usecs = 0; + vi->intr_coal_tx.max_usecs = 0; + vi->intr_coal_rx.max_packets = 0; + + /* Why is this needed? + * If without this setting, consider that when VIRTIO_NET_F_NOTF_COAL is + * negotiated and napi_tx is initially true: when the user sets non tx-frames + * parameters, such as the following cmd or others, + * ethtool -C eth0 rx-usecs 10. + * Then + * 1. ethtool_set_coalesce() first calls virtnet_get_coalesce() to get + * the last parameters except rx-usecs. If tx-frames has never been set before, + * virtnet_get_coalesce() returns with tx-frames=0 in the parameters. + * 2. virtnet_set_coalesce() is then called, according to 1: + * ec->tx_max_coalesced_frames=0. Now napi_tx switching condition is met. + * 3. If the device is up, the user setting fails: + * "netlink error: Device or resource busy" + * This is not intuitive. Therefore, we keep napi_tx state consistent with + * tx-frames when VIRTIO_NET_F_NOTF_COAL is negotiated. This behavior is + * compatible with before. + */ + if (vi->sq[0].napi.weight) + vi->intr_coal_tx.max_packets = 1; + else + vi->intr_coal_tx.max_packets = 0; + } + + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_VQ_NOTF_COAL)) { + /* The reason is the same as VIRTIO_NET_F_NOTF_COAL. */ + for (i = 0; i < vi->max_queue_pairs; i++) + if (vi->sq[i].napi.weight) + vi->sq[i].intr_coal.max_packets = 1; + } + #ifdef CONFIG_SYSFS if (vi->mergeable_rx_bufs) dev->sysfs_rx_queue_group = &virtio_net_mrg_rx_group;
--
2.19.1.6.gb485710b