[PATCH AUTOSEL 3.18 43/98] perf/rapl: Fix sysfs_show() initialization for RAPL PMU

Sasha Levin
2018-10-25T14:17:58Z

From: Stephane Eranian <eranian@google.com>

[ Upstream commit 433678bdc6ed39f053c55da96b51de5bf0aeebb1 ]

This patch fixes a problem with the initialization of the
sysfs_show() routine for the RAPL PMU.

The current code was wrongly relying on the EVENT_ATTR_STR()
macro which uses the events_sysfs_show() function in the x86
PMU code. That function itself was relying on the x86_pmu data
structure. Yet RAPL and the core PMU (x86_pmu) have nothing to
do with each other. They should therefore not interact with
each other.

The x86_pmu structure is initialized at boot time based on
the host CPU model. When the host CPU is not supported, the
x86_pmu remains uninitialized and some of the callbacks it
contains are NULL.

The false dependency with x86_pmu could potentially cause crashes
in case the x86_pmu is not initialized while the RAPL PMU is. This
may, for instance, be the case in virtualized environments.

This patch fixes the problem by using a private sysfs_show()
routine for exporting the RAPL PMU events.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150113225953.GA21525@thinkpad
Cc: vincent.weaver@maine.edu
Cc: jolsa@redhat.com
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/cpu/perf_event_intel_rapl.c | 44 +++++++++++++++------
1 file changed, 32 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 611d821eac1a..040915c87cb6 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -103,6 +103,13 @@ static struct kobj_attribute format_attr_##_var = \

#define RAPL_CNTR_WIDTH 32 /* 32-bit rapl counters */

+#define RAPL_EVENT_ATTR_STR(_name, v, str) \
+static struct perf_pmu_events_attr event_attr_##v = { \
+ .attr = __ATTR(_name, 0444, rapl_sysfs_show, NULL), \
+ .id = 0, \
+ .event_str = str, \
+};
+
struct rapl_pmu {
spinlock_t lock;
int hw_unit; /* 1/2^hw_unit Joule */
@@ -383,23 +390,36 @@ static struct attribute_group rapl_pmu_attr_group = {
.attrs = rapl_pmu_attrs,
};

-EVENT_ATTR_STR(energy-cores, rapl_cores, "event=0x01");
-EVENT_ATTR_STR(energy-pkg , rapl_pkg, "event=0x02");
-EVENT_ATTR_STR(energy-ram , rapl_ram, "event=0x03");
-EVENT_ATTR_STR(energy-gpu , rapl_gpu, "event=0x04");
+static ssize_t rapl_sysfs_show(struct device *dev,
+ struct device_attribute *attr,
+ char *page)
+{
+ struct perf_pmu_events_attr *pmu_attr = \
+ container_of(attr, struct perf_pmu_events_attr, attr);
+
+ if (pmu_attr->event_str)
+ return sprintf(page, "%s", pmu_attr->event_str);
+
+ return 0;
+}
+
+RAPL_EVENT_ATTR_STR(energy-cores, rapl_cores, "event=0x01");
+RAPL_EVENT_ATTR_STR(energy-pkg , rapl_pkg, "event=0x02");
+RAPL_EVENT_ATTR_STR(energy-ram , rapl_ram, "event=0x03");
+RAPL_EVENT_ATTR_STR(energy-gpu , rapl_gpu, "event=0x04");

-EVENT_ATTR_STR(energy-cores.unit, rapl_cores_unit, "Joules");
-EVENT_ATTR_STR(energy-pkg.unit , rapl_pkg_unit, "Joules");
-EVENT_ATTR_STR(energy-ram.unit , rapl_ram_unit, "Joules");
-EVENT_ATTR_STR(energy-gpu.unit , rapl_gpu_unit, "Joules");
+RAPL_EVENT_ATTR_STR(energy-cores.unit, rapl_cores_unit, "Joules");
+RAPL_EVENT_ATTR_STR(energy-pkg.unit , rapl_pkg_unit, "Joules");
+RAPL_EVENT_ATTR_STR(energy-ram.unit , rapl_ram_unit, "Joules");
+RAPL_EVENT_ATTR_STR(energy-gpu.unit , rapl_gpu_unit, "Joules");

/*
* we compute in 0.23 nJ increments regardless of MSR
*/
-EVENT_ATTR_STR(energy-cores.scale, rapl_cores_scale, "2.3283064365386962890625e-10");
-EVENT_ATTR_STR(energy-pkg.scale, rapl_pkg_scale, "2.3283064365386962890625e-10");
-EVENT_ATTR_STR(energy-ram.scale, rapl_ram_scale, "2.3283064365386962890625e-10");
-EVENT_ATTR_STR(energy-gpu.scale, rapl_gpu_scale, "2.3283064365386962890625e-10");
+RAPL_EVENT_ATTR_STR(energy-cores.scale, rapl_cores_scale, "2.3283064365386962890625e-10");
+RAPL_EVENT_ATTR_STR(energy-pkg.scale, rapl_pkg_scale, "2.3283064365386962890625e-10");
+RAPL_EVENT_ATTR_STR(energy-ram.scale, rapl_ram_scale, "2.3283064365386962890625e-10");
+RAPL_EVENT_ATTR_STR(energy-gpu.scale, rapl_gpu_scale, "2.3283064365386962890625e-10");

static struct attribute *rapl_events_srv_attr[] = {
EVENT_PTR(rapl_cores),
--
2.17.1