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RE: [Xen-devel] [PATCH 0/4] HVM Virtual S3

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH 0/4] HVM Virtual S3
From: "Yu, Ke" <ke.yu@xxxxxxxxx>
Date: Thu, 17 May 2007 10:32:30 +0800
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Thread-topic: [Xen-devel] [PATCH 0/4] HVM Virtual S3
Keir Fraser  wrote on 2007年5月17日 6:30:
> On 16/5/07 17:48, "Yu, Ke" <ke.yu@xxxxxxxxx> wrote:
>> - apply this patch to changeset 15050:05c128b0188a
>> - create and boot HVM domain
>> - In HVM guest, enter S3 state
>>   * for Linux, "echo mem >/sys/power/state"
>>   * for Windows, shutdown windows by Standby
>> - to resume HVM domain, "xm resume <domid>"
> Noone's seriously going to want to use S3-S5 in this way though, are
> they. Keeping domains hanging around in sleep states taking up memory
> doesn't make sense -- users will want to save the domain off to disc
> and restore later. So this only makes sense at all if integrated with
> existing HVM save/restore.
> As I understand it, the only difference between S3 and S5 is that RAM
> contents are maintained when the machine awakens. In this case S3 is
> like a simpler version of current save/restore where we do not
> necessarily need to save device state (but we might decide to if it
> makes the implementation easier).
> I think actually this isn't far off from being what we want. If the
> s3_suspend hypercall put the domain into suspend state, this would
> then neatly trigger xc_save to do its stuff. Then you can strip out
> s3_resume because you should automatically start executing BIOS code
> when xc_resume restores VCPU state and kicks the domain to start
> running again. The sleep_state domain variable you added shouldn't be
> necessary imo. 
>  -- Keir

My concern here is that: save/restore is a heavy operation just like S4 
(hibernate), while the purpose of S3 is quick suspend and quick resume comapred 
to S4. if we implement S3 like save/restore, I don't see the value here, 
because HVM save/resotre or HVM S4 is just enough. How do you think?

Best Regards

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