Re: [PATCH v4 4/6] vduse-blk: implements vduse-blk export

[Yongji Xie]

On Wed, Apr 27, 2022 at 9:22 PM Kevin Wolf <kwolf@redhat.com> wrote:
>
> Am 27.04.2022 um 05:11 hat Yongji Xie geschrieben:
> > On Wed, Apr 27, 2022 at 1:03 AM Kevin Wolf <kwolf@redhat.com> wrote:
> > >
> > > Am 06.04.2022 um 09:59 hat Xie Yongji geschrieben:
> > > > 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>
> > >
> > > The request handling code is almos the same as for the vhost-user-blk
> > > export. I wonder if we could share this code instead of copying.
> > >
> >
> > I think we can. Will do it v5.
> >
> > > The main difference seems to be that you chose not to support discard
> > > and write_zeroes yet. I'm curious if there is a reason why the
> > > vhost-user-blk code wouldn't work for vdpa there?
> > >
> >
> > They are different protocols. The data plane is similar, so we can
> > share some codes. But the control plane is different, e.g., vhost-user
> > can only work for guests but vdpa can work for both guests and hosts.
>
> Yes, sure, but discard/write_zeroes are part of the data plane, no?
> You're already sharing (or at the moment copying) the code for the other
> request types mostly unchanged, so I wondered what is different about
> discard/write_zeroes.
>

I get your point. There is no limitation on discard/write_zeroes
support for vduse. I will do it in v5.

Thanks,
Yongji