On 2025/04/16 14:46, Jason Wang wrote:
On Thu, Apr 10, 2025 at 3:42 PM Akihiko Odaki <akihiko.od...@daynix.com> wrote:
virtio-net expects set_features() will be called when the feature set
used by the guest changes to update the number of virtqueues. Call it
during reset as reset clears all features and the queues added for
VIRTIO_NET_F_MQ or VIRTIO_NET_F_RSS will need to be removed.
It's not clear to me what kind of problem we want to fix here. For
example, what happens if we don't do this.
Without this change, if the device gets reset after VIRTIO_NET_F_MQ or
VIRTIO_NET_F_RSS is configured:
- the guest will see too many virtqueues
- migration results in segfault due to the mismatch with the number of
virtqueues and feature set
I'll add the description to the patch message with the next version.
Fixes: f9d6dbf0bf6e ("virtio-net: remove virtio queues if the guest doesn't support
multiqueue")
Buglink: https://issues.redhat.com/browse/RHEL-73842
Cc: qemu-sta...@nongnu.org
Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
---
hw/virtio/virtio.c | 86 +++++++++++++++++++++++++++---------------------------
1 file changed, 43 insertions(+), 43 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 85110bce3744..033e87cdd3b9 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2316,49 +2316,6 @@ void virtio_queue_enable(VirtIODevice *vdev, uint32_t
queue_index)
}
}
-void virtio_reset(void *opaque)
-{
- VirtIODevice *vdev = opaque;
- VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
- int i;
-
- virtio_set_status(vdev, 0);
- if (current_cpu) {
- /* Guest initiated reset */
- vdev->device_endian = virtio_current_cpu_endian();
- } else {
- /* System reset */
- vdev->device_endian = virtio_default_endian();
- }
-
- if (k->get_vhost) {
- struct vhost_dev *hdev = k->get_vhost(vdev);
- /* Only reset when vhost back-end is connected */
- if (hdev && hdev->vhost_ops) {
- vhost_reset_device(hdev);
- }
- }
-
- if (k->reset) {
- k->reset(vdev);
- }
-
- vdev->start_on_kick = false;
- vdev->started = false;
- vdev->broken = false;
- vdev->guest_features = 0;
- vdev->queue_sel = 0;
- vdev->status = 0;
- vdev->disabled = false;
- qatomic_set(&vdev->isr, 0);
- vdev->config_vector = VIRTIO_NO_VECTOR;
- virtio_notify_vector(vdev, vdev->config_vector);
-
- for(i = 0; i < VIRTIO_QUEUE_MAX; i++) {
- __virtio_queue_reset(vdev, i);
- }
-}
-
void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr)
{
if (!vdev->vq[n].vring.num) {
@@ -3169,6 +3126,49 @@ int virtio_set_features(VirtIODevice *vdev, uint64_t val)
return ret;
}
+void virtio_reset(void *opaque)
+{
+ VirtIODevice *vdev = opaque;
+ VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
+ int i;
+
+ virtio_set_status(vdev, 0);
+ if (current_cpu) {
+ /* Guest initiated reset */
+ vdev->device_endian = virtio_current_cpu_endian();
+ } else {
+ /* System reset */
+ vdev->device_endian = virtio_default_endian();
+ }
+
+ if (k->get_vhost) {
+ struct vhost_dev *hdev = k->get_vhost(vdev);
+ /* Only reset when vhost back-end is connected */
+ if (hdev && hdev->vhost_ops) {
+ vhost_reset_device(hdev);
+ }
+ }
+
+ if (k->reset) {
+ k->reset(vdev);
+ }
+
+ vdev->start_on_kick = false;
+ vdev->started = false;
+ vdev->broken = false;
+ virtio_set_features_nocheck(vdev, 0);
I would just add a forward declaration instead for a smaller changset
to ease the review and backport.
Moving virtio_reset() indeed requires a bigger change, but I still want
to move it to the latter part of this file. I occasionally saw that
functions that affect the whole device state like this calls a number of
static functions. Moving virtio_reset() requires more lines to change
now, but I hope it will minimize the possibility to require forward
declarations or code movement in the future.
Regards,
Akihiko Odaki
+ vdev->queue_sel = 0;
+ vdev->status = 0;
+ vdev->disabled = false;
+ qatomic_set(&vdev->isr, 0);
+ vdev->config_vector = VIRTIO_NO_VECTOR;
+ virtio_notify_vector(vdev, vdev->config_vector);
+
+ for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
+ __virtio_queue_reset(vdev, i);
+ }
+}
+
static void virtio_device_check_notification_compatibility(VirtIODevice *vdev,
Error **errp)
{
---
base-commit: 825b96dbcee23d134b691fc75618b59c5f53da32
change-id: 20250406-reset-5ed5248ee3c1
Best regards,
--
Akihiko Odaki <akihiko.od...@daynix.com>
Thanks
