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

[Yongji Xie]

On Mon, Mar 21, 2022 at 9:25 PM Eric Blake <eblake@redhat.com> wrote:
>
> 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.
>

Yes, it must be [512, PAGE_SIZE]. I will document it in v4.

> > +#
> > +# Since: 7.0
>
> This is a new feature, and is too late for 7.0, so this line should
> mention 7.1.
>

Oh, right. I will fix it.

> > +##
> > +{ '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.
>

Will fix it.

Thanks,
Yongji