linux-kernel - RE: [PATCH 6/7] Drivers: hv: vmbus: Suspend/resume the vmbus itself for hibernation

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Message-ID: <PU1P153MB0169B839BF81829C6572C02CBFDF0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Wed, 31 Jul 2019 00:16:17 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Michael Kelley <mikelley@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 6/7] Drivers: hv: vmbus: Suspend/resume the vmbus itself
 for hibernation

> From: Michael Kelley <mikelley@...rosoft.com>
> Sent: Tuesday, July 30, 2019 4:26 PM
> From: Dexuan Cui <decui@...rosoft.com>  Sent: Monday, July 8, 2019 10:30
> PM
> >
> > This is needed when we resume the old kernel from the "current" kernel.
> 
> Perhaps a bit more descriptive commit message could be supplied?

I'll use this as the new changelog:

Before Linux enters hibernation, it sends the CHANNELMSG_UNLOAD message to
the host so all the offers are gone. After hibernation, Linux needs to re-negotiate
with the host using the same vmbus protocol version (which was in use
before hibernation), and ask the host to re-offer the vmbus devices. 

> > +
> > +	ret = vmbus_negotiate_version(msginfo, vmbus_proto_version);
> 
> I think this code answers my earlier question:  Upon resume, we negotiate
> the same
> VMbus protocol version we had at time of hibernation, even if running on a
> newer
> version of Hyper-V that might support newer protocol versions.  Hence the
> offer
> messages should not have any previously reserved fields now being used.   A
> comment to this effect would be useful.

Ok, let me add a comment before the line.

I'll post a v2 of the patchset, including the "[PATCH 4/7]", which needs a small change.

Thanks,
-- Dexuan