Messages in this thread | | | Date | Fri, 20 Jun 2014 19:43:45 +0200 | From | Borislav Petkov <> | Subject | Re: [RFC][PATCH 3/3] x86: make MP a required-feature on 64-bit |
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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 2¢ only.
-- Regards/Gruss, Boris.
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