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Subject[tip:perf/core] perf/x86: Add MSR probe interface
Commit-ID:  98253a546a468d88b7e782ab67cdf447d3c7bbe2
Gitweb: https://git.kernel.org/tip/98253a546a468d88b7e782ab67cdf447d3c7bbe2
Author: Jiri Olsa <jolsa@kernel.org>
AuthorDate: Sun, 16 Jun 2019 16:03:51 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 24 Jun 2019 19:28:31 +0200

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>
---
arch/x86/events/Makefile | 2 +-
arch/x86/events/probe.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
arch/x86/events/probe.h | 29 +++++++++++++++++++++++++++++
3 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/Makefile b/arch/x86/events/Makefile
index 9cbfd34042d5..9e07f554333f 100644
--- a/arch/x86/events/Makefile
+++ b/arch/x86/events/Makefile
@@ -1,5 +1,5 @@
# 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/
diff --git a/arch/x86/events/probe.c b/arch/x86/events/probe.c
new file mode 100644
index 000000000000..c2ede2f3b277
--- /dev/null
+++ b/arch/x86/events/probe.c
@@ -0,0 +1,45 @@
+// 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);
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__ */
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