I tested this patch with virtio-net regression tests, everything works fine.
Tested-by: Lei Yang <leiy...@redhat.com>
On Sat, May 10, 2025 at 3:25 PM Akihiko Odaki <akihiko.od...@daynix.com> wrote:
>
> virtio_net_pre_load_queues() inspects vdev->guest_features to tell if
> VIRTIO_NET_F_RSS or VIRTIO_NET_F_MQ is enabled to infer the required
> number of queues. This works for VIRTIO_NET_F_MQ but it doesn't for
> VIRTIO_NET_F_RSS because only the lowest 32 bits of vdev->guest_features
> is set at the point and VIRTIO_NET_F_RSS uses bit 60 while
> VIRTIO_NET_F_MQ uses bit 22.
>
> Instead of inferring the required number of queues from
> vdev->guest_features, use the number loaded from the vm state.
>
> Fixes: 8c49756825da ("virtio-net: Add only one queue pair when realizing")
> Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
> ---
> include/hw/virtio/virtio.h | 2 +-
> hw/net/virtio-net.c | 11 ++++-------
> hw/virtio/virtio.c | 14 +++++++-------
> 3 files changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 638691028050..af52580c1e63 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -211,7 +211,7 @@ struct VirtioDeviceClass {
> 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);
> + int (*pre_load_queues)(VirtIODevice *vdev, uint32_t n);
> /* 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 de87cfadffe1..c25c6cf54183 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -3026,11 +3026,10 @@ static void virtio_net_del_queue(VirtIONet *n, int
> index)
> virtio_del_queue(vdev, index * 2 + 1);
> }
>
> -static void virtio_net_change_num_queue_pairs(VirtIONet *n, int
> new_max_queue_pairs)
> +static void virtio_net_change_num_queues(VirtIONet *n, int new_num_queues)
> {
> VirtIODevice *vdev = VIRTIO_DEVICE(n);
> int old_num_queues = virtio_get_num_queues(vdev);
> - int new_num_queues = new_max_queue_pairs * 2 + 1;
> int i;
>
> assert(old_num_queues >= 3);
> @@ -3066,16 +3065,14 @@ static void virtio_net_set_multiqueue(VirtIONet *n,
> int multiqueue)
> int max = multiqueue ? n->max_queue_pairs : 1;
>
> n->multiqueue = multiqueue;
> - virtio_net_change_num_queue_pairs(n, max);
> + virtio_net_change_num_queues(n, max * 2 + 1);
>
> virtio_net_set_queue_pairs(n);
> }
>
> -static int virtio_net_pre_load_queues(VirtIODevice *vdev)
> +static int virtio_net_pre_load_queues(VirtIODevice *vdev, uint32_t n)
> {
> - 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));
> + virtio_net_change_num_queues(VIRTIO_NET(vdev), n);
>
> return 0;
> }
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 85110bce3744..286648fe9b60 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -3255,13 +3255,6 @@ 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) {
> @@ -3269,6 +3262,13 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int
> version_id)
> return -1;
> }
>
> + if (vdc->pre_load_queues) {
> + ret = vdc->pre_load_queues(vdev, num);
> + if (ret) {
> + return ret;
> + }
> + }
> +
> for (i = 0; i < num; i++) {
> vdev->vq[i].vring.num = qemu_get_be32(f);
> if (k->has_variable_vring_alignment) {
>
> ---
> base-commit: 825b96dbcee23d134b691fc75618b59c5f53da32
> change-id: 20250406-n-ae7be0389382
>
> Best regards,
> --
> Akihiko Odaki <akihiko.od...@daynix.com>
>
>
