Re: [PATCH net-next 3/4] virtio_net: Use new RSS config structs

[Akihiko Odaki]

On 2025/03/19 10:43, Jason Wang wrote:
> On Tue, Mar 18, 2025 at 5:57 PM Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
> > The new RSS configuration structures allow easily constructing data for
> > VIRTIO_NET_CTRL_MQ_RSS_CONFIG as they strictly follow the order of data
> > for the command.
> >
> > Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
> > ---
> >   drivers/net/virtio_net.c | 117 +++++++++++++++++------------------------------
> >   1 file changed, 43 insertions(+), 74 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index d1ed544ba03a..4153a0a5f278 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -360,24 +360,7 @@ struct receive_queue {
> >          struct xdp_buff **xsk_buffs;
> >   };
> >
> > -/* This structure can contain rss message with maximum settings for indirection table and keysize
> > - * Note, that default structure that describes RSS configuration virtio_net_rss_config
> > - * contains same info but can't handle table values.
> > - * In any case, structure would be passed to virtio hw through sg_buf split by parts
> > - * because table sizes may be differ according to the device configuration.
> > - */
> >   #define VIRTIO_NET_RSS_MAX_KEY_SIZE     40
> > -struct virtio_net_ctrl_rss {
> > -       __le32 hash_types;
> > -       __le16 indirection_table_mask;
> > -       __le16 unclassified_queue;
> > -       __le16 hash_cfg_reserved; /* for HASH_CONFIG (see virtio_net_hash_config for details) */
> > -       __le16 max_tx_vq;
> > -       u8 hash_key_length;
> > -       u8 key[VIRTIO_NET_RSS_MAX_KEY_SIZE];
> > -
> > -       __le16 *indirection_table;
> > -};
> >
> >   /* Control VQ buffers: protected by the rtnl lock */
> >   struct control_buf {
> > @@ -421,7 +404,9 @@ struct virtnet_info {
> >          u16 rss_indir_table_size;
> >          u32 rss_hash_types_supported;
> >          u32 rss_hash_types_saved;
> > -       struct virtio_net_ctrl_rss rss;
> > +       struct virtio_net_rss_config_hdr *rss_hdr;
> > +       struct virtio_net_rss_config_trailer rss_trailer;
> > +       u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
> >
> >          /* Has control virtqueue */
> >          bool has_cvq;
> > @@ -523,23 +508,16 @@ enum virtnet_xmit_type {
> >          VIRTNET_XMIT_TYPE_XSK,
> >   };
> >
> > -static int rss_indirection_table_alloc(struct virtio_net_ctrl_rss *rss, u16 indir_table_size)
> > +static size_t virtnet_rss_hdr_size(const struct virtnet_info *vi)
> >   {
> > -       if (!indir_table_size) {
> > -               rss->indirection_table = NULL;
> > -               return 0;
> > -       }
> > +       u16 indir_table_size = vi->has_rss ? vi->rss_indir_table_size : 1;
> >
> > -       rss->indirection_table = kmalloc_array(indir_table_size, sizeof(u16), GFP_KERNEL);
> > -       if (!rss->indirection_table)
> > -               return -ENOMEM;
> > -
> > -       return 0;
> > +       return struct_size(vi->rss_hdr, indirection_table, indir_table_size);
> >   }
> >
> > -static void rss_indirection_table_free(struct virtio_net_ctrl_rss *rss)
> > +static size_t virtnet_rss_trailer_size(const struct virtnet_info *vi)
> >   {
> > -       kfree(rss->indirection_table);
> > +       return struct_size(&vi->rss_trailer, hash_key_data, vi->rss_key_size);
> >   }
> >
> >   /* We use the last two bits of the pointer to distinguish the xmit type. */
> > @@ -3576,15 +3554,16 @@ static void virtnet_rss_update_by_qpairs(struct virtnet_info *vi, u16 queue_pair
> >
> >          for (; i < vi->rss_indir_table_size; ++i) {
> >                  indir_val = ethtool_rxfh_indir_default(i, queue_pairs);
> > -               vi->rss.indirection_table[i] = cpu_to_le16(indir_val);
> > +               vi->rss_hdr->indirection_table[i] = cpu_to_le16(indir_val);
> >          }
> > -       vi->rss.max_tx_vq = cpu_to_le16(queue_pairs);
> > +       vi->rss_trailer.max_tx_vq = cpu_to_le16(queue_pairs);
> >   }
> >
> >   static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
> >   {
> >          struct virtio_net_ctrl_mq *mq __free(kfree) = NULL;
> > -       struct virtio_net_ctrl_rss old_rss;
> > +       struct virtio_net_rss_config_hdr *old_rss_hdr;
> > +       struct virtio_net_rss_config_trailer old_rss_trailer;
> >          struct net_device *dev = vi->dev;
> >          struct scatterlist sg;
> >
> > @@ -3599,24 +3578,28 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
> >           * update (VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET below) and return directly.
> >           */
> >          if (vi->has_rss && !netif_is_rxfh_configured(dev)) {
> > -               memcpy(&old_rss, &vi->rss, sizeof(old_rss));
> > -               if (rss_indirection_table_alloc(&vi->rss, vi->rss_indir_table_size)) {
> > -                       vi->rss.indirection_table = old_rss.indirection_table;
> > +               old_rss_hdr = vi->rss_hdr;
> > +               old_rss_trailer = vi->rss_trailer;
> > +               vi->rss_hdr = kmalloc(virtnet_rss_hdr_size(vi), GFP_KERNEL);
> > +               if (!vi->rss_hdr) {
> > +                       vi->rss_hdr = old_rss_hdr;
> >                          return -ENOMEM;
> >                  }
> >
> > +               *vi->rss_hdr = *old_rss_hdr;
> >                  virtnet_rss_update_by_qpairs(vi, queue_pairs);
> >
> >                  if (!virtnet_commit_rss_command(vi)) {
> >                          /* restore ctrl_rss if commit_rss_command failed */
> > -                       rss_indirection_table_free(&vi->rss);
> > -                       memcpy(&vi->rss, &old_rss, sizeof(old_rss));
> > +                       kfree(vi->rss_hdr);
> > +                       vi->rss_hdr = old_rss_hdr;
> > +                       vi->rss_trailer = old_rss_trailer;
> >
> >                          dev_warn(&dev->dev, "Fail to set num of queue pairs to %d, because committing RSS failed\n",
> >                                   queue_pairs);
> >                          return -EINVAL;
> >                  }
> > -               rss_indirection_table_free(&old_rss);
> > +               kfree(old_rss_hdr);
> >                  goto succ;
> >          }
> >
> > @@ -4059,28 +4042,12 @@ static int virtnet_set_ringparam(struct net_device *dev,
> >   static bool virtnet_commit_rss_command(struct virtnet_info *vi)
> >   {
> >          struct net_device *dev = vi->dev;
> > -       struct scatterlist sgs[4];
> > -       unsigned int sg_buf_size;
> > +       struct scatterlist sgs[2];
> >
> >          /* prepare sgs */
> > -       sg_init_table(sgs, 4);
> > -
> > -       sg_buf_size = offsetof(struct virtio_net_ctrl_rss, hash_cfg_reserved);
> > -       sg_set_buf(&sgs[0], &vi->rss, sg_buf_size);
> > -
> > -       if (vi->has_rss) {
> > -               sg_buf_size = sizeof(uint16_t) * vi->rss_indir_table_size;
> > -               sg_set_buf(&sgs[1], vi->rss.indirection_table, sg_buf_size);
> > -       } else {
> > -               sg_set_buf(&sgs[1], &vi->rss.hash_cfg_reserved, sizeof(uint16_t));
> > -       }
> > -
> > -       sg_buf_size = offsetof(struct virtio_net_ctrl_rss, key)
> > -                       - offsetof(struct virtio_net_ctrl_rss, max_tx_vq);
> > -       sg_set_buf(&sgs[2], &vi->rss.max_tx_vq, sg_buf_size);
> > -
> > -       sg_buf_size = vi->rss_key_size;
> > -       sg_set_buf(&sgs[3], vi->rss.key, sg_buf_size);
> > +       sg_init_table(sgs, 2);
> > +       sg_set_buf(&sgs[0], vi->rss_hdr, virtnet_rss_hdr_size(vi));
> > +       sg_set_buf(&sgs[1], &vi->rss_trailer, virtnet_rss_trailer_size(vi));
>
> So I still see this:
>
>          if (vi->has_rss || vi->has_rss_hash_report) {
>                  if (!virtnet_commit_rss_command(vi)) {
>
> Should we introduce a hash config helper instead?

I think it's fine to use virtnet_commit_rss_command() for hash 
reporting. struct virtio_net_hash_config and struct 
virtio_net_rss_config are defined to have a common layout to allow 
sharing this kind of logic.

Regards,
Akihiko Odaki

> Thanks