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From: Dexuan Cui <decui@microsoft.com>
To: vkuznets <vkuznets@redhat.com>
Cc: KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	"wei.liu@kernel.org" <wei.liu@kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Michael Kelley <mikelley@microsoft.com>
Subject: RE: [PATCH] Drivers: hv: vmbus: Disallow the freeze PM operation
Date: Wed, 8 Apr 2020 17:43:35 +0000	[thread overview]
Message-ID: <HK0P153MB02732CCBDFA879FCE5CA48C7BFC00@HK0P153MB0273.APCP153.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <877dyq2d4p.fsf@vitty.brq.redhat.com>

> From: Vitaly Kuznetsov <vkuznets@redhat.com>
> Sent: Wednesday, April 8, 2020 8:47 AM
> > IMO 'freeze' in a Linux VM on Hyper-V is not really useful in practice,
> > so let's disallow the operation for both Gen-1 and Gen-2 VMs, even if
> > it's not an issue for Gen-1 VMs.
> 
> Suspend-to-idle may not be very useful indeed, however, it worked before
> and I think we can just fix it.

How can we fix Suspend-to-idle for a Gen-2 VM, in which no device can work
as wakeup devices? Note: in the case of Suspend-to-idle, now all the vmbus
devices including the synthetic keyboard/mouse are suspended completely.

Are you suggesting hv_vmbus should distinguish Suspend-to-idle from
hibernation, and for the former hv_vmbus should not suspend the synthetic
keyboard/mouse? 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. :-)

> 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?

> > +/*
> > + * Note: "freeze/suspend" here means "systemctl suspend".
> > + * "systemctl hibernate" is still supported.
> 
> Let's not use systemd terminology in kernel, let's use the ones from
> admin-guide/pm/sleep-states.rst (Suspend-to-Idle/Standby/Suspend-to-RAM/
> Hibernation).
> --
> Vitaly

Thanks! I'll use the accurate terms.

Thanks,
-- Dexuan

  reply	other threads:[~2020-04-08 17:43 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-07 22:01 [PATCH] Drivers: hv: vmbus: Disallow the freeze PM operation Dexuan Cui
2020-04-08 15:47 ` Vitaly Kuznetsov
2020-04-08 17:43   ` Dexuan Cui [this message]
2020-04-08 19:24     ` Vitaly Kuznetsov
2020-04-08 19:42       ` Dexuan Cui

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