Messages in this thread | | | Date | Fri, 20 Jun 2014 10:47:22 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [RFC][PATCH 3/3] x86: make MP a required-feature on 64-bit |
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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 2¢ 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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