linux-kernel - Re: [RFT] x86 acpi: normalize segment descriptor register on resume

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Message-ID: <487A62B3.8010207@zytor.com>
Date:	Sun, 13 Jul 2008 13:16:51 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Andy Lutomirski <luto@...ealbox.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>,
	public-kernel-testers-u79uwXL29TY76Z2rM5mHXA@...gmane.org,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Pavel Machek <pavel@....cz>
Subject: Re: [RFT] x86 acpi: normalize segment descriptor register on resume

Andi Kleen wrote:
> 
> Hmm, but the change was not supposed to break the s3 bios. Something
> fishy is going on. It sounds like the s3 bios relies on some earlier
> segment register setup.
> 
> If true this means the segment register reset would need to be moved
> later after S3 bios ran. Saving/restoring is unfortunately not possible
> because we cannot save/restore the hidden state loaded from the GDT earlier.
> 

That really doesn't make sense, though.  The VESA BIOS has to be entered 
in clean real mode; it's designed to be entered from reset, after all. 
There is definitely something fishy going on, but I don't think this 
particular aspect is it.

What's *really* odd is that this was required with the old code but 
doesn't work at all with the new code.  The former is understandable, 
the latter is not.

	-hpa
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