Subject: Re: [2.6.21.1] resume doesn't run suspended kernel?
From: Nigel Cunningham <nigel@nigel.suspend2.net>
Reply-To: nigel@nigel.suspend2.net
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>, Bill Davidsen <davidsen@tmr.com>,
       Linux Kernel M/L <linux-kernel@vger.kernel.org>
In-Reply-To: <200705281957.38954.rjw@sisk.pl>
References: <4658B7DD.3060309@tmr.com> <465AD746.7090008@tmr.com>
	 <20070528132625.GQ18807@elf.ucw.cz>  <200705281957.38954.rjw@sisk.pl>
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Date: Tue, 29 May 2007 08:48:02 +1000
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Hi.

On Mon, 2007-05-28 at 19:57 +0200, Rafael J. Wysocki wrote:
> On Monday, 28 May 2007 15:26, Pavel Machek wrote:
> > Hi!
> >=20
> > > >That's clear, I'll have to use xen or kvm or similar which restores=20
> > > >the system as suspended. Thanks for the clarification of the limitat=
ions.
> > > >
> > > Sorry, I wrote that late at night and quickly. I should have said=20
> > > "design decision" rather than "limitation," For systems which don't d=
o=20
> > > multiple kernels it's not an issue.
> > >=20
> > > I certainly would not have made the same decision, but I didn't write=
=20
> > > the code. It seems more robust to save everything than to try to=20
> > > identify what has and hasn't changed in a modular kernel.
> >=20
> > We rely on atomic copy routine not moving inside the kernel. Yes, it
> > would be possible to copy it to "known good" address and gain ability
> > to resume different kernels. Actually it should not be _that_ hard.
>=20
> Yup.  Don't we do something like this for the (ACPI-based) suspend to RAM
> already?

Yeah, I was thinking about this overnight too. It should be doable. In
addition to what we already do, I think you'd want:

- to copy the assembly to do the copying to a safe page;
- to put the location of the cpu state that was saved in the image
header so that it can be used after the data is copied back;
- to copy the nosave data to a 'safe' page.

What else?

Regards,

Nigel

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