Re: [PATCH v2] docs: Update vhost-user spec regarding backend program conventions

[Marc-André Lureau]

Hi

On Wed, Mar 11, 2020 at 3:19 PM Boeuf, Sebastien
<address@hidden> wrote:
>
> Hi!
>
> On Fri, 2020-03-06 at 13:52 +0100, Marc-André Lureau wrote:
> > Hi
> >
> > On Fri, Mar 6, 2020 at 1:35 PM Stefan Hajnoczi <address@hidden>
> > wrote:
> > > On Mon, Feb 24, 2020 at 07:24:54PM +0100, Sebastien Boeuf wrote:
> > > > The vhost-user specification is not clearly stating the expected
> > > > behavior from a backend program whenever the client disconnects.
> > > >
> > > > This patch addresses the issue by defining the default behavior
> > > > and
> > > > proposing an alternative through a command line option.
> > > >
> > > > By default, a backend program will terminate whenever the client
> > > > disconnects, unless told otherwise through the newly introduced
> > > > option --keep-listening.
> > > >
> > > > Signed-off-by: Sebastien Boeuf <address@hidden>
> > > > Signed-off-by: Stefan Hajnoczi <address@hidden>
> > > > ---
> > > >  docs/interop/vhost-user.rst | 12 ++++++++++++
> > > >  1 file changed, 12 insertions(+)
> > >
> > > Perhaps --keep-listening should be optional?
> >
> > I think it should be optional, and flagged by a capability.
>
> Could you please elaborate on that? How can I do that?

Some backend options or behavior are optional, and advertised through
--print-capabilities.

Say --foo (optional),

--print-capabilities should have something like:

{ ...
  "features": [
     "foo",
     ...
   ]
}

The list of capabilities is documented in vhost-user.json,
VHostUserBackendCapabilities.

We lack common enum such as @VHostUserBackendCommonFeature at this
point, but it can be added.

Although we don't currently parse this file through qapi, I don't know
how to express that
VHostUserBackendGPUFeature/VHostUserBackendCapabilitiesInput inherits
from another enum. Markus, any idea?



>
> Thanks,
> Sebastien
> >
> > > If the maintainers are happy with the patch as is then so am I:
> > >
> > > Reviewed-by: Stefan Hajnoczi <address@hidden>
> >
> >
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-- 
Marc-André Lureau