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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Andrea Parri <parri.andrea@gmail.com>,
        Dexuan Cui <decui@microsoft.com>
Cc:     "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv\@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Sasha Levin <sashal@kernel.org>,
        Michael Kelley <mikelley@microsoft.com>
Subject: Re: [PATCH 0/2] Drivers: hv: vmbus: Miscellaneous improvements
In-Reply-To: <20191008150847.GA15276@andrea>
References: <20191007163115.26197-1-parri.andrea@gmail.com> <PU1P153MB01691E9B0DD83E521B1E12C0BF9B0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM> <20191008150847.GA15276@andrea>
Date:   Tue, 08 Oct 2019 21:47:18 +0200
Message-ID: <87imozyq7t.fsf@vitty.brq.redhat.com>
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Andrea Parri <parri.andrea@gmail.com> writes:

> On Mon, Oct 07, 2019 at 05:41:10PM +0000, Dexuan Cui wrote:
>> > From: linux-hyperv-owner@vger.kernel.org
>> > <linux-hyperv-owner@vger.kernel.org> On Behalf Of Andrea Parri
>> > Sent: Monday, October 7, 2019 9:31 AM
>> >=20
>> > Hi all,
>> >=20
>> > The patchset:
>> >=20
>> > - simplifies/refactors the VMBus negotiation code by introducing
>> >   the table of VMBus protocol versions (patch 1/2),
>> >=20
>> > - enables VMBus protocol versions 5.1 and 5.2 (patch 2/2).
>> >=20
>> > Thanks,
>> >   Andrea
>> >=20
>> > Andrea Parri (2):
>> >   Drivers: hv: vmbus: Introduce table of VMBus protocol versions
>> >   Drivers: hv: vmbus: Enable VMBus protocol versions 5.1 and 5.2
>>=20
>> Should we add a module parameter to allow the user to specify a lower
>> protocol version, when the VM runs on the latest host?=20
>>=20
>> 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.=20
>
> 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.

--=20
Vitaly