Re: [RFC v2 08/14] virtio-net: detect VirtIONet status mid-migration change

[Eugenio Perez Martin <eperezma@redhat.com>]

On Tue, Mar 24, 2026 at 5:23 PM Jonah Palmer <jonah.palmer@oracle.com> wrote:
>
>
>
> On 3/24/26 7:26 AM, Eugenio Perez Martin wrote:
> > On Fri, Mar 20, 2026 at 3:21 PM Jonah Palmer <jonah.palmer@oracle.com> wrote:
> >>
> >> Save VirtIONet's status field during early migration and compare it
> >> again during stop-and-copy.
> >>
> >> VirtIONet keeps its own status bits here, including VIRTIO_NET_S_LINK_UP
> >> and VIRTIO_NET_S_ANNOUNCE.
> >>
> >
> > These are particular to the device, so we don't need to migrate them.
> > If any, we should check if the destination device changed the link
> > state so we can update the guest, but we don't do that as far as I
> > know.
> >
>
> Sorry I might be misunderstanding something, but isn't VirtIONet's
> status member being migrated today (vmstate_virtio_net_device)?
>

Nevermind, I was too vhost-vdpa centric with this comment :).
Migrating it in the general case is ok.

> >> Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
> >> ---
> >>   hw/net/virtio-net.c            | 6 ++++++
> >>   include/hw/virtio/virtio-net.h | 2 ++
> >>   2 files changed, 8 insertions(+)
> >>
> >> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >> index 2dd130777e..88ce33b1d2 100644
> >> --- a/hw/net/virtio-net.c
> >> +++ b/hw/net/virtio-net.c
> >> @@ -3872,6 +3872,7 @@ static int virtio_net_early_pre_save(void *opaque)
> >>       VirtIONetMigration *vnet_mig = n->migration;
> >>
> >>       vdev_mig->status_early = vdev->status;
> >> +    vnet_mig->status_early = n->status;
> >>
> >>       /* VirtIODevice config buffer snapshot */
> >>       g_free(vdev_mig->config_early);
> >> @@ -4304,6 +4305,11 @@ static bool virtio_net_has_delta(VirtIONet *n, VirtIODevice *vdev)
> >>           return true;
> >>       }
> >>
> >> +    /* Has the VirtIONet's status changed? */
> >> +    if (n->status != vnet_mig->status_early) {
> >> +        return true;
> >> +    }
> >> +
> >>       /* Has the VirtIONet's MAC info changed? */
> >>       if (memcmp(n->mac, vnet_mig->mac_early, ETH_ALEN) != 0) {
> >>           return true;
> >> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
> >> index 1e1f1a3995..59345f1811 100644
> >> --- a/include/hw/virtio/virtio-net.h
> >> +++ b/include/hw/virtio/virtio-net.h
> >> @@ -169,6 +169,7 @@ typedef struct VirtIONetQueue {
> >>
> >>   /**
> >>    * struct VirtIONetMigration - VirtIONet migration structure
> >> + * @status_early: VirtIONet status snapshot.
> >>    * @mac_early: MAC address early migration snapshot.
> >>    * @mtable_in_use_early: In-use MAC table entries.
> >>    * @mtable_uni_overflow_early: Unicast overflow MAC table entries.
> >> @@ -176,6 +177,7 @@ typedef struct VirtIONetQueue {
> >>    * @mtable_macs_early: MAC table entries.
> >>    */
> >>   typedef struct VirtIONetMigration {
> >> +    uint16_t status_early;
> >>       uint8_t mac_early[ETH_ALEN];
> >>       uint32_t mtable_in_use_early;
> >>       uint8_t mtable_uni_overflow_early;
> >> --
> >> 2.51.0
> >>
> >
>