On Mon, Aug 31, 2015 at 03:59:08PM +0300, Alexander Shishkin wrote: > Andi Kleen <a...@firstfloor.org> writes: > > > Alexander Shishkin <alexander.shish...@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.
What I meant is -- the kernel may crash on a older CPU that does not support CPUID 0x15. For example Broadwell doesn't have it. For CPUID you always need to check the level. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
