linux-kernel - Re: [PATCH 1/4] xenbus: move xenbus_dev

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Date:   Mon, 9 Dec 2019 12:57:40 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     "Durrant, Paul" <pdurrant@...zon.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>
Subject: Re: [PATCH 1/4] xenbus: move xenbus_dev_shutdown() into frontend
 code...

On 09.12.19 12:55, Durrant, Paul wrote:
>> -----Original Message-----
>> From: Jürgen Groß <jgross@...e.com>
>> Sent: 09 December 2019 11:34
>> To: Durrant, Paul <pdurrant@...zon.com>; linux-kernel@...r.kernel.org;
>> xen-devel@...ts.xenproject.org
>> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>; Stefano Stabellini
>> <sstabellini@...nel.org>
>> 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@...e.com>


Juergen