From: Andrey Borzenkov <arvidjaar@mail.ru>
To: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: Attempt rebooting via port CF9 if it seems to be available
Date: Wed, 12 Nov 2008 21:49:10 +0300
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Cc: Len Brown <lenb@kernel.org>, Matthew Garrett <mjg@redhat.com>,
       Ingo Molnar <mingo@elte.hu>, Avi Kivity <avi@redhat.com>,
       linux-acpi@vger.kernel.org, Len Brown <len.brown@intel.com>,
       Eduardo Habkost <ehabkost@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <007e7d616a5d1c2e16ad627d03f8b97799445e71.1226032943.git.len.brown@intel.com> <alpine.LFD.2.00.0811111802440.4480@localhost.localdomain> <491A225F.4090407@zytor.com>
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On Wednesday 12 November 2008, H. Peter Anvin wrote:
> Looking at doing the port CF9 fallback, I stumbled onto something fishy.
>=20
> I wonder if anyone here happens to have any idea why we turn off
> caching in machine_real_restart()?  Jumping to the BIOS is *not* a
> reset; we jump to the decompressed BIOS on low memory which is usually
> shadowed, not to the BIOS entry point.  In that way, it's more of an
> INIT than a reset, and disabling caching seems broken.
>=20
> Either way, here is a preliminary patch to do the CF9 if safe, and then
> falling back to keyboard reboot.  I'm a bit concerned about how to test
> it, of course; this stuff is sensitive and just about impossible to test
> except on millions of machines at once...
>=20
> If you have any machines (especially problematic ones) and find that
> this patch either helps or hurts or do nothing, please do let me know so
> I have any idea of the extent of coverage.
>=20

Works here both with default and reboot=3Dp.

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