Re: [PATCH for 9.0 07/12] vdpa: set backend capabilities at vhost_vdpa_init

[Jason Wang]

On Sat, Dec 16, 2023 at 1:28 AM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> The backend does not reset them until the vdpa file descriptor is closed
> so there is no harm in doing it only once.
>
> This allows the destination of a live migration to premap memory in
> batches, using VHOST_BACKEND_F_IOTLB_BATCH.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  hw/virtio/vhost-vdpa.c | 50 ++++++++++++++++--------------------------
>  1 file changed, 19 insertions(+), 31 deletions(-)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 449c3794b2..43f7c382b1 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -587,11 +587,25 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void 
> *opaque, Error **errp)
>      struct vhost_vdpa *v = opaque;
>      assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
>      trace_vhost_vdpa_init(dev, v->shared, opaque);
> +    uint64_t backend_features;
> +    uint64_t qemu_backend_features = 0x1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2 |
> +                                     0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH |
> +                                     0x1ULL << VHOST_BACKEND_F_IOTLB_ASID |
> +                                     0x1ULL << VHOST_BACKEND_F_SUSPEND;
>      int ret;
>
>      v->dev = dev;
>      dev->opaque =  opaque ;
>      v->shared->listener = vhost_vdpa_memory_listener;
> +
> +    if (vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES, &backend_features)) 
> {
> +        return -EFAULT;
> +    }
> +
> +    backend_features &= qemu_backend_features;
> +
> +    dev->backend_cap = backend_features;
> +    v->shared->backend_cap = backend_features;
>      vhost_vdpa_init_svq(dev, v);
>
>      error_propagate(&dev->migration_blocker, v->migration_blocker);
> @@ -599,6 +613,11 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void 
> *opaque, Error **errp)
>          return 0;
>      }
>
> +    ret = vhost_vdpa_call(dev, VHOST_SET_BACKEND_FEATURES, 
> &backend_features);
> +    if (ret) {
> +        return -EFAULT;
> +    }
> +
>      /*
>       * If dev->shadow_vqs_enabled at initialization that means the device has
>       * been started with x-svq=on, so don't block migration
> @@ -829,36 +848,6 @@ static int vhost_vdpa_set_features(struct vhost_dev *dev,
>      return vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
>  }
>
> -static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)

How about keeping this function but just calling it in vhost_vdpa_init()?

Thanks