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Date:   Mon, 11 Jan 2021 11:05:57 +0000
From:   Wei Liu <wei.liu@kernel.org>
To:     Michael Kelley <mikelley@microsoft.com>
Cc:     Dexuan Cui <decui@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        vkuznets <vkuznets@redhat.com>,
        "marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>
Subject: Re: [PATCH v3] Drivers: hv: vmbus: Add /sys/bus/vmbus/hibernation
Message-ID: <20210111110557.bvh6iym7575lgrko@liuwe-devbox-debian-v2>
References: <20210107014552.14234-1-decui@microsoft.com>
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On Thu, Jan 07, 2021 at 06:08:51PM +0000, Michael Kelley wrote:
> From: Dexuan Cui <decui@microsoft.com> Sent: Wednesday, January 6, 2021 5:46 PM
> > 
> > When a Linux VM runs on Hyper-V, if the host toolstack doesn't support
> > hibernation for the VM (this happens on old Hyper-V hosts like Windows
> > Server 2016, or new Hyper-V hosts if the admin or user doesn't declare
> > the hibernation intent for the VM), the VM is discouraged from trying
> > hibernation (because the host doesn't guarantee that the VM's virtual
> > hardware configuration will remain exactly the same across hibernation),
> > i.e. the VM should not try to set up the swap partition/file for
> > hibernation, etc.
> > 
> > x86 Hyper-V uses the presence of the virtual ACPI S4 state as the
> > indication of the host toolstack support for a VM. Currently there is
> > no easy and reliable way for the userspace to detect the presence of
> > the state (see https://lkml.org/lkml/2020/12/11/1097).  Add
> > /sys/bus/vmbus/hibernation for this purpose.
> > 
> > Signed-off-by: Dexuan Cui <decui@microsoft.com>
[...]
> 
> Reviewed-by: Michael Kelley <mikelley@microsoft.com>

Queued for hyperv-next. Thanks.

Wei.

>