On 06/20/2014 10:43 AM, Borislav Petkov wrote:
> On Fri, Jun 20, 2014 at 09:37:57AM -0700, H. Peter Anvin wrote:
>> We probably should just the cpu_has_mp macro entirely. All it is used
>> for is printing a warning in amd_k7_smp_check().
>>
>> Andi, Borislav -- as far as I can tell, we have *never* enforced this on
>> the 64-bit kernel, although we have enforced it on 64-bit processors
>> running the 32-bit kernel. We should either enforce it on both or just
>> drop it. What is your opinion?
>
> Well, my AMD CPUID guide says CPUID Fn8000_0001_EDX[19] is reserved,
> i.e. that X86_FEATURE_MP bit will be probably cleared.
>
> And so it is, on my F15h AMD it is not set:
>
> eax in: 0x80000001, eax = 00600f20 ebx = 10000000 ecx = 01ebbfff edx =
> 2fd3fbff
> ^
> ----------|
>
> So I don't think we should enforce it on 64-bit.
>
> I guess we can leave the check in amd_k7_smp_check() though but remove that
> nasty cpu_has_mp macro and do static_cpu_has() instead.
>
> My 2ยข only.
>
This is run before static_cpu_has().
The point, though, was that we "enforce" (taint) on 32 bits but not on
64 bits, which is clearly wrong.
My inclination is to completely kill amd_k7_smp_check() entirely, since
noone seems to know when it actually matters and it is clearly historic.
-hpa
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