This patch introduces the mechanism in which this series will use to detect VirtIODevice & VirtIONet state deltas, starting with the VirtIODevice's 'status' member of a virtio-net device.
Before we send the device's state early, we save each piece of its state in a temporary structure via virtio_net_early_pre_save. Later, once the source VM has been paused, we compare the current values of those pieces to what we saved earlier. If any mismatch is found, virtio-net's VMSD (vmstate_virtio_net) is enabled and resends all state and device prep work (as it's normally done today when live migrating a virtio-net device). Once all relevant delta checks are in place, a no-delta case will skip vmstate_virtio_net and only resend updated VQ indices. For this patch, keep a temporary always-true fallback in virtio_net_has_delta/virtio_net_needed until follow-up patches cover the remaining VirtIONet & VirtIODevice deltas. Signed-off-by: Jonah Palmer <[email protected]> --- hw/net/virtio-net.c | 40 ++++++++++++++++++++++++++++++++++++++ include/hw/virtio/virtio.h | 2 ++ 2 files changed, 42 insertions(+) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 5d71ad235e..2733e0130c 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -3864,6 +3864,16 @@ static bool failover_hide_primary_device(DeviceListener *listener, return qatomic_read(&n->failover_primary_hidden); } +static int virtio_net_early_pre_save(void *opaque) +{ + VirtIONet *n = opaque; + VirtIODevice *vdev = VIRTIO_DEVICE(n); + VirtIODevMigration *vdev_mig = vdev->migration; + + vdev_mig->status_early = vdev->status; + return 0; +} + static int virtio_net_early_pre_load(void *opaque) { VirtIONet *n = opaque; @@ -3887,6 +3897,7 @@ static const VMStateDescription vmstate_virtio_net_early = { .minimum_version_id = VIRTIO_NET_VM_VERSION, .version_id = VIRTIO_NET_VM_VERSION, .early_setup = true, + .pre_save = virtio_net_early_pre_save, .pre_load = virtio_net_early_pre_load, .post_load = virtio_net_early_post_load, .fields = (const VMStateField[]) { @@ -4231,10 +4242,39 @@ static bool dev_unplug_pending(void *opaque) return vdc->primary_unplug_pending(dev); } +static bool virtio_net_has_delta(VirtIONet *n, VirtIODevice *vdev) +{ + VirtIODevMigration *vdev_mig = vdev->migration; + + /* Has the VirtIODevice's status changed? */ + if (vdev->status != vdev_mig->status_early) { + return true; + } + + /* + * Always return true for now until we're able to detect all possible + * changes to a VirtIONet device. + */ + return true; +} + +static bool virtio_net_needed(void *opaque) +{ + VirtIONet *n = opaque; + VirtIODevice *vdev = VIRTIO_DEVICE(n); + + if (!n->early_mig) { + return true; + } + + return virtio_net_has_delta(n, vdev); +} + static const VMStateDescription vmstate_virtio_net = { .name = "virtio-net", .minimum_version_id = VIRTIO_NET_VM_VERSION, .version_id = VIRTIO_NET_VM_VERSION, + .needed = virtio_net_needed, .fields = (const VMStateField[]) { VMSTATE_VIRTIO_DEVICE, VMSTATE_END_OF_LIST() diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index 74fed8c324..752c46ce53 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -102,9 +102,11 @@ enum virtio_device_endian { /** * struct VirtIODevMigration - Common VirtIODevice migration structure * @early_load: Flag to indicate an early virtio_load for the device. + * @status_early: Device status at the time it was sent early. */ typedef struct VirtIODevMigration { bool early_load; + uint8_t status_early; } VirtIODevMigration; /** -- 2.51.0
