Messages in this thread | | | Date | Thu, 27 Nov 2008 13:42:58 -0800 | From | "H. Peter Anvin" <> | Subject | Re: oops/warning report for the week of November 26, 2008 |
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Arjan van de Ven wrote: > > diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c > index 1159e26..0044e61 100644 > --- a/arch/x86/kernel/cpu/mtrr/main.c > +++ b/arch/x86/kernel/cpu/mtrr/main.c > @@ -1567,6 +1567,8 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn) > * Make sure we only trim uncachable memory on machines that > * support the Intel MTRR architecture: > */ > + if (!cpu_has_mtrr) > + return 0; > if (!is_cpu(INTEL) || disable_mtrr_trim) > return 0; > rdmsr(MTRRdefType_MSR, def, dummy);
Okay... is_cpu() here is defined as:
#define is_cpu(vnd) (mtrr_if && mtrr_if->vendor == X86_VENDOR_##vnd)
... so an MTRR interface has been identified. Therefore testing cpu_has_mtrr is redundant.
As far as use_intel() versus is_cpu(INTEL), it looks to me as though the two are identical in the current code -- mtrr_if->vendor is never set in the generic code, and so defaults to 0 - meaning X86_VENDOR_INTEL.
All in all, it looks like the vendor ID stuff is a bad case of "works by accident" in the MTRR code, however, *given the current code* I conclude that is_cpu(INTEL) == use_intel() and that neither can be true without MTRRs enabled.
-hpa
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