Re: [PATCH v2 4/4] virtio-net: block migration if RSS feature negotiated

[Jason Wang]

On 2020/3/9 下午4:34, Yuri Benditovich wrote:
> Block migration for reference implementation of
> RSS feature in QEMU. When we add support for RSS
> on backend side, we'll implement migration of
> current RSS settings.
>
> Signed-off-by: Yuri Benditovich <address@hidden>
> ---
>   hw/net/virtio-net.c            | 18 ++++++++++++++++++
>   include/hw/virtio/virtio-net.h |  1 +
>   2 files changed, 19 insertions(+)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index abc41fdb16..943d1931a2 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -37,6 +37,7 @@
>   #include "qapi/qapi-events-migration.h"
>   #include "hw/virtio/virtio-access.h"
>   #include "migration/misc.h"
> +#include "migration/blocker.h"
>   #include "standard-headers/linux/ethtool.h"
>   #include "sysemu/sysemu.h"
>   #include "trace.h"
> @@ -627,6 +628,12 @@ static void virtio_net_reset(VirtIODevice *vdev)
>       n->announce_timer.round = 0;
>       n->status &= ~VIRTIO_NET_S_ANNOUNCE;
>   
> +    if (n->migration_blocker) {
> +        migrate_del_blocker(n->migration_blocker);
> +        error_free(n->migration_blocker);
> +        n->migration_blocker = NULL;
> +    }
> +
>       /* Flush any MAC and VLAN filter table state */
>       n->mac_table.in_use = 0;
>       n->mac_table.first_multi = 0;
> @@ -1003,6 +1010,17 @@ static void virtio_net_set_features(VirtIODevice *vdev, 
> uint64_t features)
>           vhost_net_ack_features(get_vhost_net(nc->peer), features);
>       }
>   
> +    if (virtio_has_feature(features, VIRTIO_NET_F_RSS)) {
> +        if (!n->migration_blocker) {
> +            error_setg(&n->migration_blocker, "virtio-net: RSS negotiated");
> +            migrate_add_blocker(n->migration_blocker, &err);
> +            if (err) {
> +                error_report_err(err);
> +                err = NULL;
> +            }
> +        }
> +    }


It looks to me we should add the blocker unconditionally based on 
virtio_host_has_feature() instead of depending the negotiated feature here.

Thanks


> +
>       if (virtio_has_feature(features, VIRTIO_NET_F_CTRL_VLAN)) {
>           memset(n->vlans, 0, MAX_VLAN >> 3);
>       } else {
> diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
> index 45670dd054..fba768ba9b 100644
> --- a/include/hw/virtio/virtio-net.h
> +++ b/include/hw/virtio/virtio-net.h
> @@ -180,6 +180,7 @@ struct VirtIONet {
>       virtio_net_conf net_conf;
>       NICConf nic_conf;
>       DeviceState *qdev;
> +    Error *migration_blocker;
>       int multiqueue;
>       uint16_t max_queues;
>       uint16_t curr_queues;