Re: [PATCH v3 4/6] vduse-blk: implements vduse-blk export

[Eric Blake <eblake@redhat.com>]

On Mon, Mar 21, 2022 at 03:14:37PM +0800, Xie Yongji wrote:
> This implements a VDUSE block backends based on
> the libvduse library. We can use it to export the BDSs
> for both VM and container (host) usage.
> 
> The new command-line syntax is:
> 
> $ qemu-storage-daemon \
>     --blockdev file,node-name=drive0,filename=test.img \
>     --export vduse-blk,node-name=drive0,id=vduse-export0,writable=on
> 
> After the qemu-storage-daemon started, we need to use
> the "vdpa" command to attach the device to vDPA bus:
> 
> $ vdpa dev add name vduse-export0 mgmtdev vduse
> 
> Also the device must be removed via the "vdpa" command
> before we stop the qemu-storage-daemon.
> 
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---

Looking at just the QAPI:

> +++ b/qapi/block-export.json
> @@ -170,6 +170,22 @@
>              '*allow-other': 'FuseExportAllowOther' },
>    'if': 'CONFIG_FUSE' }
>  
> +##
> +# @BlockExportOptionsVduseBlk:
> +#
> +# A vduse-blk block export.
> +#
> +# @num-queues: the number of virtqueues. Defaults to 1.
> +# @queue-size: the size of virtqueue. Defaults to 128.
> +# @logical-block-size: Logical block size in bytes. Defaults to 512 bytes.

Any restrictions on this not being allowed to be smaller than 512, or
that it must be a power of 2, or that it has a maximum size?  If so,
they should be documented.

> +#
> +# Since: 7.0

This is a new feature, and is too late for 7.0, so this line should
mention 7.1.

> +##
> +{ 'struct': 'BlockExportOptionsVduseBlk',
> +  'data': { '*num-queues': 'uint16',
> +            '*queue-size': 'uint16',
> +            '*logical-block-size': 'size'} }
> +
>  ##
>  # @NbdServerAddOptions:
>  #
> @@ -273,6 +289,7 @@
>  # @nbd: NBD export
>  # @vhost-user-blk: vhost-user-blk export (since 5.2)
>  # @fuse: FUSE export (since: 6.0)
> +# @vduse-blk: vduse-blk export (since 7.0)

Another spot for 7.1.

>  #
>  # Since: 4.2
>  ##
> @@ -280,7 +297,8 @@
>    'data': [ 'nbd',
>              { 'name': 'vhost-user-blk',
>                'if': 'CONFIG_VHOST_USER_BLK_SERVER' },
> -            { 'name': 'fuse', 'if': 'CONFIG_FUSE' } ] }
> +            { 'name': 'fuse', 'if': 'CONFIG_FUSE' },
> +            { 'name': 'vduse-blk', 'if': 'CONFIG_VDUSE_BLK_EXPORT' } ] }
>  
>  ##
>  # @BlockExportOptions:
> @@ -324,7 +342,9 @@
>        'vhost-user-blk': { 'type': 'BlockExportOptionsVhostUserBlk',
>                            'if': 'CONFIG_VHOST_USER_BLK_SERVER' },
>        'fuse': { 'type': 'BlockExportOptionsFuse',
> -                'if': 'CONFIG_FUSE' }
> +                'if': 'CONFIG_FUSE' },
> +      'vduse-blk': { 'type': 'BlockExportOptionsVduseBlk',
> +                     'if': 'CONFIG_VDUSE_BLK_EXPORT' }
>     } }
>  

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org