Re: [PATCH v3] x86: clear incorrectly forced X86_FEATURE_LAHF_LM flag

Borislav Petkov
2009-08-11T15:51:16Z

On Tue, Aug 11, 2009 at 04:37:56PM +0200, Mikael Pettersson wrote:
> Since the BIOS apparently wrote some MSR to get LAHF_LM incorrectly
> reported by CPUID, would it be possible to also correct that MSR so
> that applications that execute CPUID get the correct feature flags?

That's a good catch, actually. We have to turn off that bit in the cpuid
leaf too if the CPU doesn't support the instructions so that cpuid info
is consistent. LAHF/SAHF support in 64bit mode has to be cpuid-checked
prior to using them so that info has to be correct.

@Kevin: willing to try a patch or two?

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Regards/Gruss,
Boris.

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