Re: [PATCH v26 04/17] vfio: Add migration region initialization and finalize function

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 23 Sep 2020 04:54:06 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> Whether the VFIO device supports migration or not is decided based of
> migration region query. If migration region query is successful and migration
> region initialization is successful then migration is supported else
> migration is blocked.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  hw/vfio/meson.build           |   1 +
>  hw/vfio/migration.c           | 142 ++++++++++++++++++++++++++++++++++++++++++
>  hw/vfio/trace-events          |   5 ++
>  include/hw/vfio/vfio-common.h |   9 +++
>  4 files changed, 157 insertions(+)
>  create mode 100644 hw/vfio/migration.c

(...)

> +static int vfio_migration_region_init(VFIODevice *vbasedev, int index)
> +{
> +    VFIOMigration *migration = vbasedev->migration;
> +    Object *obj = NULL;
> +    int ret = -EINVAL;
> +
> +    obj = vbasedev->ops->vfio_get_object(vbasedev);
> +    if (!obj) {
> +        return ret;
> +    }
> +
> +    ret = vfio_region_setup(obj, vbasedev, &migration->region, index,
> +                            "migration");
> +    if (ret) {
> +        error_report("%s: Failed to setup VFIO migration region %d: %s",
> +                     vbasedev->name, index, strerror(-ret));
> +        goto err;
> +    }
> +
> +    if (!migration->region.size) {
> +        ret = -EINVAL;
> +        error_report("%s: Invalid region size of VFIO migration region %d: %s",
> +                     vbasedev->name, index, strerror(-ret));

Using strerror on a hardcoded error value is probably not terribly
helpful. I think printing either region.size (if you plan to extend
this check later) or something like "Invalid zero-sized VFIO migration
region" would make more sense.

> +        goto err;
> +    }
> +
> +    return 0;
> +
> +err:
> +    vfio_migration_region_exit(vbasedev);
> +    return ret;
> +}

(...)

Apart from that, looks good to me.