Messages in this thread | | | From | Alexander Shishkin <> | Subject | Re: [PATCH] perf/x86/intel/pt: Export cpu frequency ratios needed by PT decoders | Date | Mon, 31 Aug 2015 15:59:08 +0300 |
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Andi Kleen <andi@firstfloor.org> writes:
> Alexander Shishkin <alexander.shishkin@linux.intel.com> writes: >> + return sprintf(page, "%lu\n", val); >> + case 1: >> + cpuid(0x15, &eax, &ebx, &ecx, &edx); > > Surely this needs to be protected by a cpuid level check? > Broadwell for once doesn't have CPUID 0x15.
I couldn't find where this is explicitly said in the SDM. However, the leaf description says that CPUID.0x15.EBX[31:0]==0 means that the ratio is not enumerated. I don't see how to better communicate this to userspace though than to simply have 0 there.
Regards, -- Alex
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