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

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Mar 10, 2020 at 11:12:05AM +0800, Jason Wang wrote:
> 
> 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 <yuri.benditovich@daynix.com>
> > ---
> >   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

I agree, this is a stopgap measure anyway.  If this is merged in its
current form, there should also be a big TODO here that we must fix this
ASAP, and maybe a warning produced.


> 
> > +
> >       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;