Commit 98253a54 authored Jun 16, 2019 by Jiri Olsa Committed by Ingo Molnar Jun 24, 2019

perf/x86: Add MSR probe interface



Adding perf_msr_probe function to provide interface for
checking up on MSR register and set the related attribute
group visibility.

User defines following struct for each MSR register:

  struct perf_msr {
       u64                       msr;
       struct attribute_group   *grp;
       bool                    (*test)(int idx, void *data);
       bool                      no_check;
  };

Where:
  msr      - is the MSR address
  attrs    - is attribute groups array to add if the check passed
  test     - is test function pointer
  no_check - is bool that bypass the check and adds the
              attribute without any test

The array of struct perf_msr is passed into:

  perf_msr_probe(struct perf_msr *msr, int cnt, bool zero, void *data)

Together with:
  cnt  - which is the number of struct msr array elements
  data - which is user pointer passed to the test function
  zero - allow counters that returns zero on rdmsr

The perf_msr_probe will executed test code, read the MSR and
check the value is != 0. If all these tests pass, related
attribute group is kept visible.

Also adding PMU_EVENT_GROUP macro helper to define attribute
group for single attribute. It will be used in following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan <kan.liang@linux.intel.com>
Cc: Liang
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lkml.kernel.org/r/20190616140358.27799-2-jolsa@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 9e6e87e6

arch/x86/events/Makefile

+1 −1

Original line number	Diff line number	Diff line
		# SPDX-License-Identifier: GPL-2.0-only
		obj-y += core.o
		obj-y += core.o probe.o
		obj-y += amd/
		obj-$(CONFIG_X86_LOCAL_APIC) += msr.o
		obj-$(CONFIG_CPU_SUP_INTEL) += intel/

arch/x86/events/probe.c

0 → 100644

+45 −0

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0
		#include <linux/export.h>
		#include <linux/types.h>
		#include <linux/bits.h>
		#include "probe.h"

		static umode_t
		not_visible(struct kobject kobj, struct attribute attr, int i)
		{
		return 0;
		}

		unsigned long
		perf_msr_probe(struct perf_msr msr, int cnt, bool zero, void data)
		{
		unsigned long avail = 0;
		unsigned int bit;
		u64 val;

		if (cnt >= BITS_PER_LONG)
		return 0;

		for (bit = 0; bit < cnt; bit++) {
		if (!msr[bit].no_check) {
		struct attribute_group *grp = msr[bit].grp;

		grp->is_visible = not_visible;

		if (msr[bit].test && !msr[bit].test(bit, data))
		continue;
		/* Virt sucks; you cannot tell if a R/O MSR is present :/ */
		if (rdmsrl_safe(msr[bit].msr, &val))
		continue;
		/* Disable zero counters if requested. */
		if (!zero && !val)
		continue;

		grp->is_visible = NULL;
		}
		avail \|= BIT(bit);
		}

		return avail;
		}
		EXPORT_SYMBOL_GPL(perf_msr_probe);

arch/x86/events/probe.h

0 → 100644

+29 −0

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0 */
		#ifndef __ARCH_X86_EVENTS_PROBE_H__
		#define __ARCH_X86_EVENTS_PROBE_H__
		#include <linux/sysfs.h>

		struct perf_msr {
		u64 msr;
		struct attribute_group *grp;
		bool (test)(int idx, void data);
		bool no_check;
		};

		unsigned long
		perf_msr_probe(struct perf_msr msr, int cnt, bool no_zero, void data);

		#define __PMU_EVENT_GROUP(_name) \
		static struct attribute *attrs_##_name[] = { \
		&attr_##_name.attr.attr, \
		NULL, \
		}

		#define PMU_EVENT_GROUP(_grp, _name) \
		__PMU_EVENT_GROUP(_name); \
		static struct attribute_group group_##_name = { \
		.name = #_grp, \
		.attrs = attrs_##_name, \
		}

		#endif /* __ARCH_X86_EVENTS_PROBE_H__ */