Andrew Melnichenko
2022-Feb-17 19:02 UTC
[PATCH v3 2/4] drivers/net/virtio_net: Added basic RSS support.
Hi all, On Mon, Feb 14, 2022 at 12:09 AM Willem de Bruijn <willemdebruijn.kernel at gmail.com> wrote:> > > > > @@ -3113,13 +3270,14 @@ static int virtnet_probe(struct virtio_device *vdev) > > > > u16 max_queue_pairs; > > > > int mtu; > > > > > > > > - /* Find if host supports multiqueue virtio_net device */ > > > > - err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ, > > > > - struct virtio_net_config, > > > > - max_virtqueue_pairs, &max_queue_pairs); > > > > + /* Find if host supports multiqueue/rss virtio_net device */ > > > > + max_queue_pairs = 1; > > > > + if (virtio_has_feature(vdev, VIRTIO_NET_F_MQ) || virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) > > > > + max_queue_pairs > > > > + virtio_cread16(vdev, offsetof(struct virtio_net_config, max_virtqueue_pairs)); > > > > > > Instead of testing either feature and treating them as somewhat equal, > > > shouldn't RSS be dependent on MQ? > > > > No, RSS is dependent on CTRL_VQ. Technically RSS and MQ are similar features. > > RSS depends on having multiple queues. > > What would enabling VIRTIO_NET_F_RSS without VIRTIO_NET_F_MQ do?RSS would work. According to virtio spec article 5.1.6.5.5:> A device MAY support one of these features or both. The driver MAY negotiate any set of these features > that the device supports.Also, in 5.1.3.1:> VIRTIO_NET_F_RSS Requires VIRTIO_NET_F_CTRL_VQ.> > > > > > > > > > > > /* We need at least 2 queue's */ > > > > - if (err || max_queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN || > > > > + if (max_queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN || > > > > max_queue_pairs > VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MAX || > > > > !virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) > > > > max_queue_pairs = 1; > > > > @@ -3207,6 +3365,23 @@ static int virtnet_probe(struct virtio_device *vdev) > > > > if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) > > > > vi->mergeable_rx_bufs = true; > > > > > > > > + if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) { > > > > + vi->has_rss = true; > > > > + vi->rss_indir_table_size > > > > + virtio_cread16(vdev, offsetof(struct virtio_net_config, > > > > + rss_max_indirection_table_length)); > > > > + vi->rss_key_size > > > > + virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size)); > > > > + > > > > + vi->rss_hash_types_supported > > > > + virtio_cread32(vdev, offsetof(struct virtio_net_config, supported_hash_types)); > > > > + vi->rss_hash_types_supported &> > > > + ~(VIRTIO_NET_RSS_HASH_TYPE_IP_EX | > > > > + VIRTIO_NET_RSS_HASH_TYPE_TCP_EX | > > > > + VIRTIO_NET_RSS_HASH_TYPE_UDP_EX); > > > > + > > > > + dev->hw_features |= NETIF_F_RXHASH; > > > > > > Only make the feature visible when the hash is actually reported in > > > the skb, patch 3. > > > > VirtioNET has two features: RSS(steering only) and hash(hash report in > > vnet header) > > Both features may be enabled/disabled separately: > > 1. rss on and hash off - packets steered to the corresponding vqs > > 2. rss off and hash on - packets steered by tap(like mq) but headers > > have properly calculated hash. > > 3. rss on and hash on - packets steered to corresponding vqs and hash > > is present in the header. > > > > RXHASH feature allows the user to enable/disable the rss/hash(any combination). > > I find that confusing, but.. I see that there is prior art where some > drivers enable/disable entire RSS load balancing based on this flag. > So ok. > > > I think it's a good idea to leave RXHASH in patch 2/4 to give the user > > ability to manipulate the rss only feature. > > But, if you think that it requires to move it to the 3/4, I'll do it. > > > > > > > > Also, clearly separate the feature patches (2) rss, (3) rxhash, (4) > > > rxhash config. > > > > Currently: > > Patch 2/4 - adds VirtioNet rss feature. > > Patch 3/4 - adds VirtioNet hash report feature. > > Patch 4/4 - adds the ability to manipulate supported hash types. > > > > Can you provide more detailed suggestions on how to move hunks? > > I gave one in the follow-on patch, to which you responded. That's probably it.I'll add zero size table check and move hunk for padded header length from 3/4 to 1/4.
Willem de Bruijn
2022-Feb-18 15:43 UTC
[PATCH v3 2/4] drivers/net/virtio_net: Added basic RSS support.
On Thu, Feb 17, 2022 at 12:05 PM Andrew Melnichenko <andrew at daynix.com> wrote:> > Hi all, > > On Mon, Feb 14, 2022 at 12:09 AM Willem de Bruijn > <willemdebruijn.kernel at gmail.com> wrote: > > > > > > > @@ -3113,13 +3270,14 @@ static int virtnet_probe(struct virtio_device *vdev) > > > > > u16 max_queue_pairs; > > > > > int mtu; > > > > > > > > > > - /* Find if host supports multiqueue virtio_net device */ > > > > > - err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ, > > > > > - struct virtio_net_config, > > > > > - max_virtqueue_pairs, &max_queue_pairs); > > > > > + /* Find if host supports multiqueue/rss virtio_net device */ > > > > > + max_queue_pairs = 1; > > > > > + if (virtio_has_feature(vdev, VIRTIO_NET_F_MQ) || virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) > > > > > + max_queue_pairs > > > > > + virtio_cread16(vdev, offsetof(struct virtio_net_config, max_virtqueue_pairs)); > > > > > > > > Instead of testing either feature and treating them as somewhat equal, > > > > shouldn't RSS be dependent on MQ? > > > > > > No, RSS is dependent on CTRL_VQ. Technically RSS and MQ are similar features. > > > > RSS depends on having multiple queues. > > > > What would enabling VIRTIO_NET_F_RSS without VIRTIO_NET_F_MQ do? > > RSS would work.What does that mean, exactly? RSS is load balancing, does that not require multi-queue?