linux-kernel - RE: [PATCH] Input: hyperv-keyboard: Add the support of hibernation

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Message-ID: <PU1P153MB0169CC57749BF297F2581B02BF9F0@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Thu, 3 Oct 2019 06:44:04 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: RE: [PATCH] Input: hyperv-keyboard: Add the support of hibernation

> From: Dexuan Cui
> Sent: Wednesday, October 2, 2019 10:35 PM
> > ... 
> >
> > ¯\_(ツ)_/¯ If you do not want to implement hibernation properly in vmbus
> > code that is totally up to you (have you read in pm.h how freeze() is
> > different from suspend()?).
> > Dmitry
> 
> I understand freeze() is different from suspend(). Here I treat suspend() as a
> heavyweight freeze() for simplicity and IMHO the extra cost of time is
> neglectable considering the long hibernation process, which can take
> 5~10+ seconds.
> 
> Even if I implement all the pm ops, IMO the issue we're talking about
> (i.e. the hibernation process can be aborted by user's keyboard/mouse
> activities) still exists. Actually I think a physical Linux machine should have
> the same issue.
> 
> In practice, IMO the issue is not a big concern, as the VM usually runs in
> a remote data center, and the user has no access to the VM's
> keyboard/mouse. :-)
> 
> I hope I understood your comments. I'll post a v2 without the notifier.
> Please Ack the v2 if it looks good to you.
> 
> -- Dexuan

I think I understood now: it looks the vmbus driver should implement
a prepare() or freeze(), which calls the hyperv_keyboard driver's
prepare() or freeze(), which can set the flag or disable the keyboard
event handling. This way we don't need the notifier.

Please let me know if I still don't get it right.

Thanks,
-- Dexuan