Re: [RFC 2/2] virtio-net: use post load hook

[Jason Wang]

On 2019/10/11 上午2:04, Michael S. Tsirkin wrote:
> Currently offloads disabled by guest via the VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET
> command are not preserved on VM migration.
> Instead all offloads reported by guest features (via VIRTIO_PCI_GUEST_FEATURES)
> get enabled.
> What happens is: first the VirtIONet::curr_guest_offloads gets restored
> and offloads are getting set correctly:
>
>   #0  qemu_set_offload (nc=0x555556a11400, csum=1, tso4=0, tso6=0, ecn=0, 
> ufo=0) at net/net.c:474
>   #1  virtio_net_apply_guest_offloads (n=0x555557701ca0) at 
> hw/net/virtio-net.c:720
>   #2  virtio_net_post_load_device (opaque=0x555557701ca0, version_id=11) at 
> hw/net/virtio-net.c:2334
>   #3  vmstate_load_state (f=0x5555569dc010, vmsd=0x555556577c80 
> <vmstate_virtio_net_device>, opaque=0x555557701ca0, version_id=11)
>       at migration/vmstate.c:168
>   #4  virtio_load (vdev=0x555557701ca0, f=0x5555569dc010, version_id=11) at 
> hw/virtio/virtio.c:2197
>   #5  virtio_device_get (f=0x5555569dc010, opaque=0x555557701ca0, size=0, 
> field=0x55555668cd00 <__compound_literal.5>) at hw/virtio/virtio.c:2036
>   #6  vmstate_load_state (f=0x5555569dc010, vmsd=0x555556577ce0 
> <vmstate_virtio_net>, opaque=0x555557701ca0, version_id=11) at 
> migration/vmstate.c:143
>   #7  vmstate_load (f=0x5555569dc010, se=0x5555578189e0) at 
> migration/savevm.c:829
>   #8  qemu_loadvm_section_start_full (f=0x5555569dc010, mis=0x5555569eee20) at 
> migration/savevm.c:2211
>   #9  qemu_loadvm_state_main (f=0x5555569dc010, mis=0x5555569eee20) at 
> migration/savevm.c:2395
>   #10 qemu_loadvm_state (f=0x5555569dc010) at migration/savevm.c:2467
>   #11 process_incoming_migration_co (opaque=0x0) at migration/migration.c:449
>
> However later on the features are getting restored, and offloads get reset to
> everything supported by features:
>
>   #0  qemu_set_offload (nc=0x555556a11400, csum=1, tso4=1, tso6=1, ecn=0, 
> ufo=0) at net/net.c:474
>   #1  virtio_net_apply_guest_offloads (n=0x555557701ca0) at 
> hw/net/virtio-net.c:720
>   #2  virtio_net_set_features (vdev=0x555557701ca0, features=5104441767) at 
> hw/net/virtio-net.c:773
>   #3  virtio_set_features_nocheck (vdev=0x555557701ca0, val=5104441767) at 
> hw/virtio/virtio.c:2052
>   #4  virtio_load (vdev=0x555557701ca0, f=0x5555569dc010, version_id=11) at 
> hw/virtio/virtio.c:2220
>   #5  virtio_device_get (f=0x5555569dc010, opaque=0x555557701ca0, size=0, 
> field=0x55555668cd00 <__compound_literal.5>) at hw/virtio/virtio.c:2036
>   #6  vmstate_load_state (f=0x5555569dc010, vmsd=0x555556577ce0 
> <vmstate_virtio_net>, opaque=0x555557701ca0, version_id=11) at 
> migration/vmstate.c:143
>   #7  vmstate_load (f=0x5555569dc010, se=0x5555578189e0) at 
> migration/savevm.c:829
>   #8  qemu_loadvm_section_start_full (f=0x5555569dc010, mis=0x5555569eee20) at 
> migration/savevm.c:2211
>   #9  qemu_loadvm_state_main (f=0x5555569dc010, mis=0x5555569eee20) at 
> migration/savevm.c:2395
>   #10 qemu_loadvm_state (f=0x5555569dc010) at migration/savevm.c:2467
>   #11 process_incoming_migration_co (opaque=0x0) at migration/migration.c:449
>
> Fix this by pushing out offload initialization to the new post load hook.
>
> Reported-by: Mikhail Sennikovsky <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>   hw/net/virtio-net.c | 14 ++++++++++----
>   1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 9f11422337..62fb858e2d 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -2333,10 +2333,6 @@ static int virtio_net_post_load_device(void *opaque, int 
> version_id)
>           n->curr_guest_offloads = virtio_net_supported_guest_offloads(n);
>       }
>   
> -    if (peer_has_vnet_hdr(n)) {
> -        virtio_net_apply_guest_offloads(n);
> -    }
> -
>       virtio_net_set_queues(n);
>   
>       /* Find the first multicast entry in the saved MAC filter */
> @@ -2370,6 +2366,15 @@ static int virtio_net_post_load_device(void *opaque, int 
> version_id)
>       return 0;
>   }
>   
> +static int virtio_net_post_load_virtio(VirtIODevice *vdev)
> +{
> +    if (peer_has_vnet_hdr(n)) {
> +        virtio_net_apply_guest_offloads(n);
> +    }
> +
> +    return 0;
> +}
> +
>   /* tx_waiting field of a VirtIONetQueue */
>   static const VMStateDescription vmstate_virtio_net_queue_tx_waiting = {
>       .name = "virtio-net-queue-tx_waiting",
> @@ -2912,6 +2917,7 @@ static void virtio_net_class_init(ObjectClass *klass, 
> void *data)
>       vdc->guest_notifier_mask = virtio_net_guest_notifier_mask;
>       vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;
>       vdc->legacy_features |= (0x1 << VIRTIO_NET_F_GSO);
> +    vdc->post_load = virtio_net_post_load_virtio;
>       vdc->vmsd = &vmstate_virtio_net_device;
>   }
>   


Looks good to me.

Thanks