linux-kernel - Re: [PATCH 0/2] Drivers: hv: vmbus: Miscellaneous improvements

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Message-ID: <87imozyq7t.fsf@vitty.brq.redhat.com>
Date:   Tue, 08 Oct 2019 21:47:18 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Andrea Parri <parri.andrea@...il.com>,
        Dexuan Cui <decui@...rosoft.com>
Cc:     "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv\@vger.kernel.org" <linux-hyperv@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: Re: [PATCH 0/2] Drivers: hv: vmbus: Miscellaneous improvements

Andrea Parri <parri.andrea@...il.com> writes:

> On Mon, Oct 07, 2019 at 05:41:10PM +0000, Dexuan Cui wrote:
>> > From: linux-hyperv-owner@...r.kernel.org
>> > <linux-hyperv-owner@...r.kernel.org> On Behalf Of Andrea Parri
>> > Sent: Monday, October 7, 2019 9:31 AM
>> > 
>> > Hi all,
>> > 
>> > The patchset:
>> > 
>> > - simplifies/refactors the VMBus negotiation code by introducing
>> >   the table of VMBus protocol versions (patch 1/2),
>> > 
>> > - enables VMBus protocol versions 5.1 and 5.2 (patch 2/2).
>> > 
>> > Thanks,
>> >   Andrea
>> > 
>> > Andrea Parri (2):
>> >   Drivers: hv: vmbus: Introduce table of VMBus protocol versions
>> >   Drivers: hv: vmbus: Enable VMBus protocol versions 5.1 and 5.2
>> 
>> Should we add a module parameter to allow the user to specify a lower
>> protocol version, when the VM runs on the latest host? 
>> 
>> This can be useful for testing and debugging purpose: the variable
>> "vmbus_proto_version" is referenced by the vmbus driver itself and
>> some VSC drivers: if we always use the latest available proto version,
>> some code paths can not be tested on the latest hosts. 
>
> The idea is appealing to me (altough I made no attempt to implement/test
> it yet).  What do others think about this?  Maybe can be considered as a
> follow-up patch/work to this series?

IMO such debug option makes sense, it shouldn be a simple patch so you
may want to squeeze it in this series as it will definitely have code
dependencies.

-- 
Vitaly