Re: [Qemu-devel] [PATCH v4 2/4] vhost-user-blk: introduce a new vhost-user-blk host device

[Paolo Bonzini]

On 19/10/2017 07:24, Changpeng Liu wrote:
>    ;;
>    --enable-vhost-scsi) vhost_scsi="yes"
>    ;;
> +  --disable-vhost-user-blk) vhost_user_blk="no"
> +  ;;
> +  --enable-vhost-user-blk) vhost_user_blk="yes"
> +  ;;
>    --disable-vhost-vsock) vhost_vsock="no"
>    ;;
>    --enable-vhost-vsock) vhost_vsock="yes"
> @@ -1511,6 +1517,7 @@ disabled with --disable-FEATURE, default is enabled if 
> available:
>    cap-ng          libcap-ng support
>    attr            attr and xattr support
>    vhost-net       vhost-net acceleration support
> +  vhost-user-blk  VM virtio-blk acceleration in user space

Please use default-configs instead of a new configure switch.  See how
CONFIG_VHOST_USER_SCSI is used in default-configs/pci.mak and
default-configs/s390x-softmmu.mak.

> 
> +static const int user_feature_bits[] = {
> +    VIRTIO_BLK_F_SIZE_MAX,
> +    VIRTIO_BLK_F_SEG_MAX,
> +    VIRTIO_BLK_F_GEOMETRY,
> +    VIRTIO_BLK_F_BLK_SIZE,
> +    VIRTIO_BLK_F_TOPOLOGY,
> +    VIRTIO_BLK_F_SCSI,

Please omit VIRTIO_BLK_F_SCSI, it's a legacy option that is not anymore
part of virtio 1.0.

> +    VIRTIO_BLK_F_MQ,
> +    VIRTIO_BLK_F_RO,
> +    VIRTIO_BLK_F_FLUSH,
> +    VIRTIO_BLK_F_BARRIER,

Same for VIRTIO_BLK_F_BARRIER.

> +    VIRTIO_BLK_F_WCE,

And VIRTIO_BLK_F_WCE is the same as VIRTIO_BLK_F_FLUSH, so it can be
removed too.  Please include VIRTIO_BLK_F_CONFIG_WCE instead, since you
are supporting it in vhost_user_blk_set_config.

> +    VIRTIO_F_VERSION_1,
> +    VIRTIO_RING_F_INDIRECT_DESC,
> +    VIRTIO_RING_F_EVENT_IDX,
> +    VIRTIO_F_NOTIFY_ON_EMPTY,
> +    VHOST_INVALID_FEATURE_BIT
> +};

> 
> +static const TypeInfo vhost_user_blk_info = {
> +    .name = TYPE_VHOST_USER_BLK,
> +    .parent = TYPE_VIRTIO_DEVICE,
> +    .instance_size = sizeof(VHostUserBlk),
> +    .instance_init = vhost_user_blk_instance_init,
> +    .class_init = vhost_user_blk_class_init,
> +};
> +

There is some code duplication, so maybe it's worth introducing a common
superclass like TYPE_VIRTIO_SCSI_COMMON.  I'll let others comment on
whether this is a requirement.

Paolo