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

[Jason Wang]

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@redhat.com>
> ---
> 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?

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;
>       }