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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>
(cherry picked from commit adda0ad56b)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Akihiko Odaki 2025-05-30 14:18:53 +09:00 • committed by Michael Tokarev
parent 6624ff3972
commit f272f318c0
3 changed files with 19 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

11
hw/net/virtio-net.c
View file

@ -3021,11 +3021,10 @@ 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);
@ -3061,16 +3060,14 @@ 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;
}

14
hw/virtio/virtio.c
View file

@ -3257,13 +3257,6 @@ 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) {
@ -3271,6 +3264,13 @@ 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) {

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.
*/