RE: [PATCH 1/4] xenbus: move xenbus_dev_shutdown() into frontend code...
From: Durrant, Paul
Date: Mon Dec 09 2019 - 06:55:32 EST
> -----Original Message-----
> From: JÃrgen GroÃ <jgross@xxxxxxxx>
> Sent: 09 December 2019 11:34
> To: Durrant, Paul <pdurrant@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>; Stefano Stabellini
> Subject: Re: [PATCH 1/4] xenbus: move xenbus_dev_shutdown() into frontend
> On 05.12.19 15:01, Paul Durrant wrote:
> > ...and make it static
> > xenbus_dev_shutdown() is seemingly intended to cause clean shutdown of
> > 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
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.