linux-kernel - Re: [tip:x86/urgent] x86, AMD: Disable wrongly set X86_FEATURE_LAHF

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Message-ID: <20090825055215.GA22595@liondog.tnic>
Date:	Tue, 25 Aug 2009 07:52:15 +0200
From:	Borislav Petkov <petkovbb@...glemail.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...e.hu>, mingo@...hat.com,
	linux-kernel@...r.kernel.org, kjwinchester@...il.com,
	tglx@...utronix.de, borislav.petkov@....com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86, AMD: Disable wrongly set
 X86_FEATURE_LAHF_LM CPUID bit

On Mon, Aug 24, 2009 at 01:34:07PM -0700, H. Peter Anvin wrote:
> Looks reasonable... although part of me wonders if having a pointer to
> an array containing the entire register file in and out is even better,
> of if I'm just overengineering at this point.

Hmm, let's have necessity determine that. I can only think of %edi being
used as an input reg to rd/wrmsr beside %ecx but it could be very well
that some other x86 hardware uses other regs too. Do we actually need
all regs or a two should suffice?

> Note that the only difference between "rdmsr" and "wrmsr" is the actual
> opcode being executed at this point...

... which means even less code with macro magic.
 
-- 
Regards/Gruss,
    Boris.
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