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

Ingo Molnar
2009-08-08T15:43:13Z

* Borislav Petkov <petkovbb@googlemail.com> wrote:

> > +
> > + /*
> > + * Some BIOSes incorrectly set this feature, but only
> > + * Revision E (with Extended Model = 2) actually supports
> > + * it.
> > + */
> > + if (!(level & 0x00020000))
> > + clear_cpu_cap(c, X86_FEATURE_LAHF_LM);
>
> let me check this internally next week because it seems that
> according to the Fam 0xf RevGuide
> (http://support.amd.com/us/Processor_TechDocs/25759.pdf) erratum
> 110 applies to atleast 3 CPU revisions with extended model 0x1
> too.

Ok, mind resending the patch (or dropping it) if you figured that
out? We need to be careful about restoring CPU erratum workarounds
that BIOSen install ... these things are very hard to test and easy
to get wrong.

Ingo