Commit 8b70c743 authored Mar 18, 2025 by Sohil Mehta Committed by Ingo Molnar Mar 19, 2025

perf/x86/intel, x86/cpu: Simplify Intel PMU initialization



Architectural Perfmon was introduced on the Family 6 "Core" processors
starting with Yonah. Processors before Yonah need their own customized
PMU initialization.

p6_pmu_init() is expected to provide that initialization for early
Family 6 processors. But, currently, it could get called for any Family
6 processor if the architectural perfmon feature is disabled on that
processor. To simplify, restrict the P6 PMU initialization to early
Family 6 processors that do not have architectural perfmon support and
truly need the special handling.

As a result, the "unsupported" console print becomes practically
unreachable because all the released P6 processors are covered by the
switch cases. Move the console print to a common location where it can
cover all modern processors (including Family >15) that may not have
architectural perfmon support enumerated.

Also, use this opportunity to get rid of the unnecessary switch cases in
P6 initialization. Only the Pentium Pro processor needs a quirk, and the
rest of the processors do not need any special handling. The gaps in the
case numbers are only due to no processor with those model numbers being
released.

Use decimal numbers to represent Intel Family numbers. Also, convert one
of the last few Intel x86_model comparisons to a VFM-based one.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250318223828.2945651-2-sohil.mehta@intel.com

parent 24a295e4

arch/x86/events/intel/core.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -6541,15 +6541,21 @@ __init int intel_pmu_init(void)
		char *name;
		struct x86_hybrid_pmu *pmu;

		/* Architectural Perfmon was introduced starting with Core "Yonah" */
		if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
		switch (boot_cpu_data.x86) {
		case 0x6:
		case 6:
		if (boot_cpu_data.x86_vfm < INTEL_CORE_YONAH)
		return p6_pmu_init();
		case 0xb:
		break;
		case 11:
		return knc_pmu_init();
		case 0xf:
		case 15:
		return p4_pmu_init();
		}

		pr_cont("unsupported CPU family %d model %d ",
		boot_cpu_data.x86, boot_cpu_data.x86_model);
		return -ENODEV;
		}

arch/x86/events/intel/p6.c

+3 −23

Original line number	Diff line number	Diff line
		@@ -2,6 +2,8 @@
		#include <linux/perf_event.h>
		#include <linux/types.h>

		#include <asm/cpu_device_id.h>

		#include "../perf_event.h"

		/*
		@@ -248,30 +250,8 @@ __init int p6_pmu_init(void)
		{
		x86_pmu = p6_pmu;

		switch (boot_cpu_data.x86_model) {
		case 1: /* Pentium Pro */
		if (boot_cpu_data.x86_vfm == INTEL_PENTIUM_PRO)
		x86_add_quirk(p6_pmu_rdpmc_quirk);
		break;

		case 3: /* Pentium II - Klamath */
		case 5: /* Pentium II - Deschutes */
		case 6: /* Pentium II - Mendocino */
		break;

		case 7: /* Pentium III - Katmai */
		case 8: /* Pentium III - Coppermine */
		case 10: /* Pentium III Xeon */
		case 11: /* Pentium III - Tualatin */
		break;

		case 9: /* Pentium M - Banias */
		case 13: /* Pentium M - Dothan */
		break;

		default:
		pr_cont("unsupported p6 CPU model %d ", boot_cpu_data.x86_model);
		return -ENODEV;
		}

		memcpy(hw_cache_event_ids, p6_hw_cache_event_ids,
		sizeof(hw_cache_event_ids));