Re: [PATCH] virtio-net: Add queues before loading them

[Michael S. Tsirkin]

On Tue, Oct 22, 2024 at 03:49:01PM +0900, Akihiko Odaki wrote:
> Call virtio_net_set_multiqueue() to add queues before loading their
> states. Otherwise the loaded queues will not have handlers and elements
> in them will not be processed.
> 
> Cc: qemu-stable@nongnu.org
> Fixes: 8c49756825da ("virtio-net: Add only one queue pair when realizing")
> Reported-by: Laurent Vivier <lvivier@redhat.com>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>


Jason, your queue?

> ---
>  include/hw/virtio/virtio.h |  2 ++
>  hw/net/virtio-net.c        | 10 ++++++++++
>  hw/virtio/virtio.c         |  7 +++++++
>  3 files changed, 19 insertions(+)
> 
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index f526ecc8fcc0..638691028050 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -210,6 +210,8 @@ struct VirtioDeviceClass {
>      void (*guest_notifier_mask)(VirtIODevice *vdev, int n, bool mask);
>      int (*start_ioeventfd)(VirtIODevice *vdev);
>      void (*stop_ioeventfd)(VirtIODevice *vdev);
> +    /* Called before loading queues. Useful to add queues before loading. */
> +    int (*pre_load_queues)(VirtIODevice *vdev);
>      /* Saving and loading of a device; trying to deprecate save/load
>       * use vmsd for new devices.
>       */
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index fb84d142ee29..c467ef130016 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -3032,6 +3032,15 @@ static void virtio_net_set_multiqueue(VirtIONet *n, 
> int multiqueue)
>      virtio_net_set_queue_pairs(n);
>  }
>  
> +static int virtio_net_pre_load_queues(VirtIODevice *vdev)
> +{
> +    virtio_net_set_multiqueue(VIRTIO_NET(vdev),
> +                              virtio_has_feature(vdev->guest_features, 
> VIRTIO_NET_F_RSS) ||
> +                              virtio_has_feature(vdev->guest_features, 
> VIRTIO_NET_F_MQ));
> +
> +    return 0;
> +}
> +
>  static int virtio_net_post_load_device(void *opaque, int version_id)
>  {
>      VirtIONet *n = opaque;
> @@ -4025,6 +4034,7 @@ static void virtio_net_class_init(ObjectClass *klass, 
> void *data)
>      vdc->guest_notifier_mask = virtio_net_guest_notifier_mask;
>      vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;
>      vdc->legacy_features |= (0x1 << VIRTIO_NET_F_GSO);
> +    vdc->pre_load_queues = virtio_net_pre_load_queues;
>      vdc->post_load = virtio_net_post_load_virtio;
>      vdc->vmsd = &vmstate_virtio_net_device;
>      vdc->primary_unplug_pending = primary_unplug_pending;
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index a26f18908ea5..f12c4aa81eb5 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -3255,6 +3255,13 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int 
> version_id)
>          config_len--;
>      }
>  
> +    if (vdc->pre_load_queues) {
> +        ret = vdc->pre_load_queues(vdev);
> +        if (ret) {
> +            return ret;
> +        }
> +    }
> +
>      num = qemu_get_be32(f);
>  
>      if (num > VIRTIO_QUEUE_MAX) {
> 
> ---
> base-commit: 7e3b6d8063f245d27eecce5aabe624b5785f2a77
> change-id: 20241017-load-fb5544456d28
> 
> Best regards,
> -- 
> Akihiko Odaki <akihiko.odaki@daynix.com>