linux-kernel - RE: [PATCH] Drivers: hv: vmbus: Disallow the freeze PM operation

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Date:   Wed, 8 Apr 2020 19:42:27 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     vkuznets <vkuznets@...hat.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: RE: [PATCH] Drivers: hv: vmbus: Disallow the freeze PM operation

> From: Vitaly Kuznetsov <vkuznets@...hat.com>
> Sent: Wednesday, April 8, 2020 12:24 PM
> To: Dexuan Cui <decui@...rosoft.com>
> > ...
> > This should be doable but IMO this is not a very trivial
> > effort, and I'm trying to avoid it since IMO Suspend-to-idle is not really
> > useful in practice for a Linux VM on Hyper-V. :-)
> 
> Well, to me it's equally (not) useful in all other cases :-) I think we
> should Cc: linux-pm@...r.kernel.org and someone will describe a real
> world usecase to educate us, we'll then see if there is any Hyper-V
> specifics.
Maybe I should support Suspend-to-idle, anyway. :-)

> >> In particular, why do we need to do
> >> anything when we are not hibernating?
> >
> > Are you suggesting hv_vmbus should not suspend the vmbus devices at all
> > in the case of Suspend-to-idle?
> 
> That what we were doing prior to the hibernation series, right? AFAIU
Yes.

> suspend-to-idle is basically 'no processes are scheduled' mode but we
> don't really need to do anything with devices.
Got it. Let me try to make a patch to revert to the old behavior for 
Suspend-to-idle.

Thanks,
-- Dexuan