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

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Message-ID: <4A8EDC02.8000508@zytor.com>
Date:	Fri, 21 Aug 2009 10:40:18 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <petkovbb@...glemail.com>,
	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 08/16/2009 02:49 PM, Borislav Petkov wrote:
> On Sun, Aug 16, 2009 at 08:41:32AM +0200, Ingo Molnar wrote:
>> -tip testing found this build bug caused by this patch:
>>
>> arch/x86/kernel/cpu/amd.c: In function ‘init_amd’:
>> arch/x86/kernel/cpu/amd.c:417: error: implicit declaration of function ‘wrmsr_amd_safe’
> 
> Oops, forgot paravirt. Here's a fixed version:
> 

One thing that really bothers me about these is that they're horribly
non-generic.  It wouldn't be so bad -- if we need something more generic
we can create them -- if it wasn't for that perennial horror called
paravirt_crap, which of course just ends up incorporating whatever
internal interfaces we have.

If we're going to modify the paravirt_crap for yet another MSR
operation, then let's at least make it something like "write_msr_edi"
and have it take a parameter for the EDI value.  Perhaps we should let
it set EBX and ESI as well (and the same for the read operation, even
though it already exists.)

	-hpa
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