Messages in this thread | | | Date | Tue, 4 Nov 2014 16:57:34 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v5 12/20] x86: perf: intel_pt: Intel PT PMU driver |
| |
On Fri, Oct 31, 2014 at 03:13:35PM +0200, Alexander Shishkin wrote: > >> + if (test_cpu_cap(&boot_cpu_data, X86_FEATURE_INTEL_PT)) { > >> + for (i = 0; i < PT_CPUID_LEAVES; i++) > >> + cpuid_count(20, i, > >> + &pt_pmu.caps[CR_EAX + i * 4], > >> + &pt_pmu.caps[CR_EBX + i * 4], > >> + &pt_pmu.caps[CR_ECX + i * 4], > >> + &pt_pmu.caps[CR_EDX + i * 4]); > >> + } else > >> + return -ENODEV; > > > > I would really rather you use bitfield unions for cpuid stuff, have a > > look at union cpuid10_e[abd]x as used in > > perf_event_intel.c:intel_pmu_init(). > > It looks like it would only work for the first cpuid leaf, but we'll > need more than that. And the array makes it easier to allocate > attributes for sysfs en masse. > > I guess it doesn't really matter if we use unions unless these bits need > to be exported to other parts of the kernel? But *that* is hardly a good > idea. What do you think?
Ah yes, the generation. C is lacking there isn't it :/
Now I'm not sure we want to export all the bits you're using though. Like the topa_multiple_entires, that appears an implementation detail userspace should not really care about either way.
| |