Re: [PATCH v4 12/15] vdpa: block migration if device has unsupported features

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On Mon, Feb 27, 2023 at 4:15 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
>
> 在 2023/2/24 23:54, Eugenio Pérez 写道:
> > A vdpa net device must initialize with SVQ in order to be migratable at
> > this moment, and initialization code verifies some conditions.  If the
> > device is not initialized with the x-svq parameter, it will not expose
> > _F_LOG so the vhost subsystem will block VM migration from its
> > initialization.
> >
> > Next patches change this, so we need to verify migration conditions
> > differently.
> >
> > QEMU only supports a subset of net features in SVQ, and it cannot
> > migrate state that cannot track or restore in the destination.  Add a
> > migration blocker if the device offer an unsupported feature.
> >
> > Signed-off-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
> > ---
> > v3: add mirgation blocker properly so vhost_dev can handle it.
> > ---
> >   net/vhost-vdpa.c | 12 ++++++++----
> >   1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> > index 4f983df000..094dc1c2d0 100644
> > --- a/net/vhost-vdpa.c
> > +++ b/net/vhost-vdpa.c
> > @@ -795,7 +795,8 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
> >                                          int nvqs,
> >                                          bool is_datapath,
> >                                          bool svq,
> > -                                       struct vhost_vdpa_iova_range iova_range)
> > +                                       struct vhost_vdpa_iova_range iova_range,
> > +                                       uint64_t features)
> >   {
> >       NetClientState *nc = NULL;
> >       VhostVDPAState *s;
> > @@ -818,7 +819,10 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
> >       s->vhost_vdpa.shadow_vqs_enabled = svq;
> >       s->vhost_vdpa.iova_range = iova_range;
> >       s->vhost_vdpa.shadow_data = svq;
> > -    if (!is_datapath) {
> > +    if (queue_pair_index == 0) {
> > +        vhost_vdpa_net_valid_svq_features(features,
> > +                                          &s->vhost_vdpa.migration_blocker);
>
>
> Since we do validation at initialization, is this necessary to valid
> once again in other places?

Ok, after reading patch 13, I think the question is:

The validation seems to be independent to net, can we valid it once
during vhost_vdpa_init()?

Thanks

>
> Thanks
>
>
> > +    } else if (!is_datapath) {
> >           s->cvq_cmd_out_buffer = qemu_memalign(qemu_real_host_page_size(),
> >                                               vhost_vdpa_net_cvq_cmd_page_len());
> >           memset(s->cvq_cmd_out_buffer, 0, vhost_vdpa_net_cvq_cmd_page_len());
> > @@ -956,7 +960,7 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
> >       for (i = 0; i < queue_pairs; i++) {
> >           ncs[i] = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
> >                                        vdpa_device_fd, i, 2, true, opts->x_svq,
> > -                                     iova_range);
> > +                                     iova_range, features);
> >           if (!ncs[i])
> >               goto err;
> >       }
> > @@ -964,7 +968,7 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
> >       if (has_cvq) {
> >           nc = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
> >                                    vdpa_device_fd, i, 1, false,
> > -                                 opts->x_svq, iova_range);
> > +                                 opts->x_svq, iova_range, features);
> >           if (!nc)
> >               goto err;
> >       }

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