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>

1 files changed, 29 insertions, 0 deletions

diff --git a/arch/x86/events/probe.h b/arch/x86/events/probe.h
new file mode 100644
index 000000000000..4c8e0afc5fb5
--- /dev/null
+++ b/arch/x86/events/probe.h
@@ -0,0 +1,29 @@
+/* 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__ */