Re: [PATCH 1/4] xenbus: move xenbus_dev_shutdown() into frontend code...

[JÃrgen GroÃ]

On 09.12.19 12:55, Durrant, Paul wrote:
> > -----Original Message-----
> > From: JÃrgen Groà <jgross@xxxxxxxx>
> > Sent: 09 December 2019 11:34
> > To: Durrant, Paul <pdurrant@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> > xen-devel@xxxxxxxxxxxxxxxxxxxx
> > Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>; Stefano Stabellini
> > <sstabellini@xxxxxxxxxx>
> > Subject: Re: [PATCH 1/4] xenbus: move xenbus_dev_shutdown() into frontend
> > code...
> >
> > On 05.12.19 15:01, Paul Durrant wrote:
> > > ...and make it static
> > >
> > > xenbus_dev_shutdown() is seemingly intended to cause clean shutdown of
> > PV
> > > frontends when a guest is rebooted. Indeed the function waits for a
> > > conpletion which is only set by a call to xenbus_frontend_closed().
> > >
> > > This patch removes the shutdown() method from backends and moves
> > > xenbus_dev_shutdown() from xenbus_probe.c into xenbus_probe_frontend.c,
> > > renaming it appropriately and making it static.
> >
> > Is this a good move considering driver domains?
>
> I don't think it can have ever worked properly for driver domains, and with the rest of the patches a backend should be able go away and return unannounced (as long as the domain id is kept... for which patches need to be upstreamed into Xen).
>
> > At least I'd expect the commit message addressing the expected behavior
> > with rebooting a driver domain and why this patch isn't making things
> > worse.
>
> For a clean reboot I'd expect the toolstack to shut down the protocol before rebooting the driver domain, so the backend shutdown method is moot. And I don't believe re-startable driver domains were something that ever made it into support (because of the non-persistent domid problem). I can add something to the commit comment to that effect if you'd like.

Yes, please do so.

With this you can add my:

Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen