Re: [PATCH v3 1/1] vhost-user-fs: add migration type property

[Vladimir Sementsov-Ogievskiy]

On 17.02.23 20:00, Anton Kuchin wrote:
> Migration of vhost-user-fs device requires transfer of FUSE internal state
> from backend. There is no standard way to do it now so by default migration
> must be blocked. But if this state can be externally transferred by
> orchestrator give it an option to explicitly allow migration.
>
> Signed-off-by: Anton Kuchin <antonkuchin@yandex-team.ru>
> ---
>   hw/core/qdev-properties-system.c    | 10 +++++++++
>   hw/virtio/vhost-user-fs.c           | 32 ++++++++++++++++++++++++++++-
>   include/hw/qdev-properties-system.h |  1 +
>   include/hw/virtio/vhost-user-fs.h   |  2 ++
>   qapi/migration.json                 | 16 +++++++++++++++
>   5 files changed, 60 insertions(+), 1 deletion(-)
>
> diff --git a/hw/core/qdev-properties-system.c b/hw/core/qdev-properties-system.c
> index d42493f630..d9b1aa2a5d 100644
> --- a/hw/core/qdev-properties-system.c
> +++ b/hw/core/qdev-properties-system.c
> @@ -1143,3 +1143,13 @@ const PropertyInfo qdev_prop_uuid = {
>       .set   = set_uuid,
>       .set_default_value = set_default_uuid_auto,
>   };
> +
> +const PropertyInfo qdev_prop_vhost_user_migration_type = {
> +    .name = "VhostUserMigrationType",
> +    .description = "none/external",
> +    .enum_table = &VhostUserMigrationType_lookup,
> +    .get = qdev_propinfo_get_enum,
> +    .set = qdev_propinfo_set_enum,
> +    .set_default_value = qdev_propinfo_set_default_value_enum,
> +    .realized_set_allowed = true,
> +};
> diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
> index 83fc20e49e..7deb9df5ec 100644
> --- a/hw/virtio/vhost-user-fs.c
> +++ b/hw/virtio/vhost-user-fs.c
> @@ -298,9 +298,35 @@ static struct vhost_dev *vuf_get_vhost(VirtIODevice *vdev)
>       return &fs->vhost_dev;
>   }
>   
> +static int vhost_user_fs_pre_save(void *opaque)
> +{
> +    VHostUserFS *fs = opaque;
> +    g_autofree char *path = object_get_canonical_path(OBJECT(fs));
> +
> +    switch (fs->migration_type) {
> +    case VHOST_USER_MIGRATION_TYPE_NONE:
> +        error_report("Migration is blocked by device %s", path);
> +        break;
> +    case VHOST_USER_MIGRATION_TYPE_EXTERNAL:
> +        return 0;
> +    default:
> +        error_report("Migration type '%s' is not supported by device %s",
> +                     VhostUserMigrationType_str(fs->migration_type), path);
> +        break;
> +    }
> +
> +    return -1;
> +}

Should we also add this as .pre_load, to force user select correct 
migration_type on target too?

> +
>   static const VMStateDescription vuf_vmstate = {
>       .name = "vhost-user-fs",
> -    .unmigratable = 1,
> +    .minimum_version_id = 0,
> +    .version_id = 0,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_VIRTIO_DEVICE,
> +        VMSTATE_END_OF_LIST()
> +    },
> +   .pre_save = vhost_user_fs_pre_save,
>   };
>   
>   static Property vuf_properties[] = {
> @@ -309,6 +335,10 @@ static Property vuf_properties[] = {
>       DEFINE_PROP_UINT16("num-request-queues", VHostUserFS,
>                          conf.num_request_queues, 1),
>       DEFINE_PROP_UINT16("queue-size", VHostUserFS, conf.queue_size, 128),
> +    DEFINE_PROP_UNSIGNED("migration", VHostUserFS, migration_type,
> +                         VHOST_USER_MIGRATION_TYPE_NONE,
> +                         qdev_prop_vhost_user_migration_type,
> +                         VhostUserMigrationType),

1. I see, other similar qdev_prop_* use DEFINE_PROP_SIGNED
2. All of them except only qdev_prop_fdc_drive_type, define also a convenient 
macro in include/hw/qdev-properties-system.h

should we follow these patterns?


--
Best regards,
Vladimir