linux-kernel - Re: [PATCH 3/3] x86, AMD: Disable wrongly set X86_FEATURE_LAHF

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Message-ID: <20090830193039.GB22234@liondog.tnic>
Date:	Sun, 30 Aug 2009 21:30:39 +0200
From:	Borislav Petkov <petkovbb@...glemail.com>
To:	"H. Peter Anvin" <hpa@...or.com>, #@...ndog.tnic
Cc:	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: [PATCH 3/3] x86, AMD: Disable wrongly set X86_FEATURE_LAHF_LM
 CPUID bit

On Sun, Aug 30, 2009 at 12:22:34PM -0700, H. Peter Anvin wrote:
> On 08/30/2009 04:50 AM, Borislav Petkov wrote:
> >  			clear_cpu_cap(c, X86_FEATURE_LAHF_LM);
> > +			if (!rdmsrl_amd_safe(0xc001100d, &val)) {
> > +				val &= ~(1ULL << 32);
> > +				wrmsr_amd_safe(0xc001100d, (u32) val,
> > +							   (u32)(val >> 32));
> > +			}
> > +		}
> 
> We presumably want/need wrmsrl_amd_safe() here!

Actually, it is wrmsr_amd_safe() because we need the magic value in
%edi. wrmsr_amd_safe() calls the _regs variant with the array argument.
And we don't have a wrmsrl_amd_safe-one which gets a 64bit msr value as
an argument similar to the rdmsrl one.

-- 
Regards/Gruss,
    Boris.
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