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

To: "Yu, Ke" <ke.yu@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0/4] HVM Virtual S3
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 16 May 2007 23:29:55 +0100
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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



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