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virtio-net: Add queues for RSS during migration

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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. This
change also has a nice side effect to remove a duplicate peer queue
pair change by circumventing virtio_net_set_multiqueue().

Also update the comment in include/hw/virtio/virtio.h to prevent an
implementation of pre_load_queues() from refering to any fields being
loaded during migration by accident in the future.

Fixes: 8c49756825 ("virtio-net: Add only one queue pair when realizing")

Tested-by: Lei Yang <leiyang@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
This commit is contained in:
Akihiko Odaki 2025-05-30 14:18:53 +09:00 • committed by Jason Wang
parent 110d0fa2d4
commit adda0ad56b
3 changed files with 19 additions and 16 deletions
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10
include/hw/virtio/virtio.h
View file

@ -210,8 +210,14 @@ 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);
/*
* Called before loading queues.
* If the number of queues change at runtime, use @n to know the
* number and add or remove queues accordingly.
* Note that this function is called in the middle of loading vmsd;
* no assumption should be made on states being loaded from vmsd.
*/
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.
*/