perf, x86: Provide means for disabling userspace RDPMC
Allow the disabling of RDPMC via a pmu specific attribute:
echo 0 > /sys/bus/event_source/devices/cpu/rdpmc
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Arun Sharma <asharma@fb.com>
Link: http://lkml.kernel.org/n/tip-pqeog465zo5hsimtkfz73f27@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 53b5699..116b040 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -24,6 +24,7 @@
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/bitops.h>
+#include <linux/device.h>
#include <asm/apic.h>
#include <asm/stacktrace.h>
@@ -1210,7 +1211,8 @@
break;
case CPU_STARTING:
- set_in_cr4(X86_CR4_PCE);
+ if (x86_pmu.attr_rdpmc)
+ set_in_cr4(X86_CR4_PCE);
if (x86_pmu.cpu_starting)
x86_pmu.cpu_starting(cpu);
break;
@@ -1320,6 +1322,8 @@
}
}
+ x86_pmu.attr_rdpmc = 1; /* enable userspace RDPMC usage by default */
+
pr_info("... version: %d\n", x86_pmu.version);
pr_info("... bit width: %d\n", x86_pmu.cntval_bits);
pr_info("... generic registers: %d\n", x86_pmu.num_counters);
@@ -1555,10 +1559,59 @@
return idx + 1;
}
+static ssize_t get_attr_rdpmc(struct device *cdev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ return snprintf(buf, 40, "%d\n", x86_pmu.attr_rdpmc);
+}
+
+static void change_rdpmc(void *info)
+{
+ bool enable = !!(unsigned long)info;
+
+ if (enable)
+ set_in_cr4(X86_CR4_PCE);
+ else
+ clear_in_cr4(X86_CR4_PCE);
+}
+
+static ssize_t set_attr_rdpmc(struct device *cdev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long val = simple_strtoul(buf, NULL, 0);
+
+ if (!!val != !!x86_pmu.attr_rdpmc) {
+ x86_pmu.attr_rdpmc = !!val;
+ smp_call_function(change_rdpmc, (void *)val, 1);
+ }
+
+ return count;
+}
+
+static DEVICE_ATTR(rdpmc, S_IRUSR | S_IWUSR, get_attr_rdpmc, set_attr_rdpmc);
+
+static struct attribute *x86_pmu_attrs[] = {
+ &dev_attr_rdpmc.attr,
+ NULL,
+};
+
+static struct attribute_group x86_pmu_attr_group = {
+ .attrs = x86_pmu_attrs,
+};
+
+static const struct attribute_group *x86_pmu_attr_groups[] = {
+ &x86_pmu_attr_group,
+ NULL,
+};
+
static struct pmu pmu = {
.pmu_enable = x86_pmu_enable,
.pmu_disable = x86_pmu_disable,
+ .attr_groups = x86_pmu_attr_groups,
+
.event_init = x86_pmu_event_init,
.add = x86_pmu_add,
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index 8944062..513d617 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -307,6 +307,14 @@
struct x86_pmu_quirk *quirks;
int perfctr_second_write;
+ /*
+ * sysfs attrs
+ */
+ int attr_rdpmc;
+
+ /*
+ * CPU Hotplug hooks
+ */
int (*cpu_prepare)(int cpu);
void (*cpu_starting)(int cpu);
void (*cpu_dying)(int cpu);
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 02545e6..5311b79 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -615,6 +615,7 @@
struct list_head entry;
struct device *dev;
+ const struct attribute_group **attr_groups;
char *name;
int type;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 05affc3..dcd4049e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5505,6 +5505,7 @@
if (!pmu->dev)
goto out;
+ pmu->dev->groups = pmu->attr_groups;
device_initialize(pmu->dev);
ret = dev_set_name(pmu->dev, "%s", pmu->name);
if (ret)
