On Wed, Apr 3, 2024 at 2:11 PM Akihiko Odaki <akihiko.od...@daynix.com> wrote:
>
> vhost requires eBPF for RSS. When eBPF is not available, virtio-net
> implicitly disables RSS even if the user explicitly requests it. Return
> an error instead of implicitly disabling RSS if RSS is requested but not
> available.
>
> Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
> ---
> hw/net/virtio-net.c | 97
> ++++++++++++++++++++++++++---------------------------
> 1 file changed, 48 insertions(+), 49 deletions(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 61b49e335dea..3d53eba88cfc 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -793,9 +793,6 @@ static uint64_t virtio_net_get_features(VirtIODevice
> *vdev, uint64_t features,
> return features;
> }
>
> - if (!ebpf_rss_is_loaded(&n->ebpf_rss)) {
> - virtio_clear_feature(&features, VIRTIO_NET_F_RSS);
> - }
> features = vhost_net_get_features(get_vhost_net(nc->peer), features);
> vdev->backend_features = features;
>
> @@ -3591,6 +3588,50 @@ static bool
> failover_hide_primary_device(DeviceListener *listener,
> return qatomic_read(&n->failover_primary_hidden);
> }
>
> +static void virtio_net_device_unrealize(DeviceState *dev)
> +{
> + VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> + VirtIONet *n = VIRTIO_NET(dev);
> + int i, max_queue_pairs;
> +
> + if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
> + virtio_net_unload_ebpf(n);
> + }
> +
> + /* This will stop vhost backend if appropriate. */
> + virtio_net_set_status(vdev, 0);
> +
> + g_free(n->netclient_name);
> + n->netclient_name = NULL;
> + g_free(n->netclient_type);
> + n->netclient_type = NULL;
> +
> + g_free(n->mac_table.macs);
> + g_free(n->vlans);
> +
> + if (n->failover) {
> + qobject_unref(n->primary_opts);
> + device_listener_unregister(&n->primary_listener);
> + migration_remove_notifier(&n->migration_state);
> + } else {
> + assert(n->primary_opts == NULL);
> + }
> +
> + max_queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
> + for (i = 0; i < max_queue_pairs; i++) {
> + virtio_net_del_queue(n, i);
> + }
> + /* delete also control vq */
> + virtio_del_queue(vdev, max_queue_pairs * 2);
> + qemu_announce_timer_del(&n->announce_timer, false);
> + g_free(n->vqs);
> + qemu_del_nic(n->nic);
> + virtio_net_rsc_cleanup(n);
> + g_free(n->rss_data.indirections_table);
> + net_rx_pkt_uninit(n->rx_pkt);
> + virtio_cleanup(vdev);
> +}
> +
> static void virtio_net_device_realize(DeviceState *dev, Error **errp)
> {
> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> @@ -3760,53 +3801,11 @@ static void virtio_net_device_realize(DeviceState
> *dev, Error **errp)
>
> net_rx_pkt_init(&n->rx_pkt);
>
> - if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
> - virtio_net_load_ebpf(n);
> - }
> -}
> -
> -static void virtio_net_device_unrealize(DeviceState *dev)
> -{
> - VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> - VirtIONet *n = VIRTIO_NET(dev);
> - int i, max_queue_pairs;
> -
> - if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
> - virtio_net_unload_ebpf(n);
> + if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS) &&
I disagree with this change of qemu behavior.
>From my point of view:
- this is not a major problem and it should not be a reason to stop VM execution
- it is enough to disable the RSS feature and continue working. Depending on
other qemu parameters (number of queues, number of cpus) this might be just
suboptimal. might be a minor problem and might be not a problem at all
- this change defines rss as _only_ feature whose absence breaks the VM start,
_all_ other features are dropped silently and only rss is not. Why??
- the series has a title 'Fixes and improvements' . This is not a fix and not an
improvement, this is significant behavioral change that should be discussed in
light of future plans regarding rss
- I suggest to remove this change from the series, submit it separately
and discuss from all the sides
> + !virtio_net_load_ebpf(n) && get_vhost_net(nc->peer)) {
> + virtio_net_device_unrealize(dev);
> + error_setg(errp, "Can't load eBPF RSS for vhost");
> }
> -
> - /* This will stop vhost backend if appropriate. */
> - virtio_net_set_status(vdev, 0);
> -
> - g_free(n->netclient_name);
> - n->netclient_name = NULL;
> - g_free(n->netclient_type);
> - n->netclient_type = NULL;
> -
> - g_free(n->mac_table.macs);
> - g_free(n->vlans);
> -
> - if (n->failover) {
> - qobject_unref(n->primary_opts);
> - device_listener_unregister(&n->primary_listener);
> - migration_remove_notifier(&n->migration_state);
> - } else {
> - assert(n->primary_opts == NULL);
> - }
> -
> - max_queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
> - for (i = 0; i < max_queue_pairs; i++) {
> - virtio_net_del_queue(n, i);
> - }
> - /* delete also control vq */
> - virtio_del_queue(vdev, max_queue_pairs * 2);
> - qemu_announce_timer_del(&n->announce_timer, false);
> - g_free(n->vqs);
> - qemu_del_nic(n->nic);
> - virtio_net_rsc_cleanup(n);
> - g_free(n->rss_data.indirections_table);
> - net_rx_pkt_uninit(n->rx_pkt);
> - virtio_cleanup(vdev);
> }
>
> static void virtio_net_reset(VirtIODevice *vdev)
>
> --
> 2.44.0
>
