Re: [PATCH net] virtio_net: sync rss_trailer.max_tx_vq on queue_pairs change via VQ_PAIRS_SET

[Paolo Abeni <pabeni@redhat.com>]

On 4/16/26 11:21 PM, Brett Creeley wrote:
> When netif_is_rxfh_configured() is true (i.e., the user has explicitly
> configured the RSS indirection table), virtnet_set_queues() skips the
> RSS update path and falls through to the VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET
> command to change the number of queue pairs. However, it does not update
> vi->rss_trailer.max_tx_vq to reflect the new queue_pairs value.
> 
> This causes a mismatch between vi->curr_queue_pairs and
> vi->rss_trailer.max_tx_vq. Any subsequent RSS reconfiguration (e.g.,
> via ethtool -X) calls virtnet_commit_rss_command(), which sends the
> stale max_tx_vq to the device, silently reverting the queue count.
> 
> Reproduction:
> 1. User configured RSS
>   ethtool -X eth0 equal 8
> 2. VQ_PAIRS_SET path; max_tx_vq stays 16
>   ethtool -L eth0 combined 12
> 3. RSS commit uses max_tx_vq=16 instead of 12
>   ethtool -X eth0 equal 4
> 
> Fix this by updating vi->rss_trailer.max_tx_vq after a successful
> VQ_PAIRS_SET command when RSS is enabled, keeping it in sync with
> curr_queue_pairs.
> 
> Fixes: 50bfcaedd78e ("virtio_net: Update rss when set queue")
> Assisted-by: Claude: claude-opus-4.6
> Signed-off-by: Brett Creeley <brett.creeley@amd.com>

The patch LGTM, but waiting a little longer just in case the virtio crew
has some comments.

/P