linux-kernel - Re: [linux-pm] [PATCH -mm] kexec jump -v9

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Message-ID: <m1k5hwzf2z.fsf@frodo.ebiederm.org>
Date:	Wed, 14 May 2008 15:38:28 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	Kexec Mailing List <kexec@...ts.infradead.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pm@...ts.linux-foundation.org,
	Vivek Goyal <vgoyal@...hat.com>,
	Len Brown <len.brown@...el.com>
Subject: Re: [linux-pm] [PATCH -mm] kexec jump -v9

"Rafael J. Wysocki" <rjw@...k.pl> writes:

> On Saturday, 22 of March 2008, Alan Stern wrote:

> The spec doesn't say much about that, so we'll need to carry out some
> experiments.

> Still, as far as I can figure out what the spec authors _might_ mean, I think
> that it would be inappropriate to restore the ACPI NVS area if S5 was entered
> on "power off".  The idea seems to be that the restoration of the ACPI NVS area
> should complement whatever has been preserved by the platform over the
> hibernation/resume cycle.

> IMO, if S5 was entered on "powe off", there are two possible ways to go.
> Either ACPI is initialized by the boot kernel, in which case the image kernel
> should not touch things like _WAK and similar, just throw away whatever
> ACPI-related state it got from the image and try to rebuild the ACPI-related
> data from scratch.  Or the boot kernel doesn't touch ACPI and the image kernel
> initializes it in the same way as during a fresh boot (that might be difficult,
> though).

Just an added data partial point.  In the kexec case I have had not heard
anyone screaming to me that ACPI doesn't work after we switch kernels.

So I expect shutting down ACPI and restarting it should work reliably
and that is easy to test as that is already implemented with kexec.

Eric
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