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Commit 0c9d42ed authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPeter 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: default avatarIngo Molnar <mingo@elte.hu>
parent fe4a3308

arch/x86/kernel/cpu/perf_event.c

+54 −1
Original line number Diff line number Diff line
@@ -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>
@@ -1210,6 +1211,7 @@ x86_pmu_notifier(struct notifier_block *self, unsigned long action, void *hcpu) 
		break;



	case CPU_STARTING:

		if (x86_pmu.attr_rdpmc)

			set_in_cr4(X86_CR4_PCE);

		if (x86_pmu.cpu_starting)

			x86_pmu.cpu_starting(cpu);
@@ -1320,6 +1322,8 @@ static int __init init_hw_perf_events(void) 
		}

	}



	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 @@ static int x86_pmu_event_idx(struct perf_event *event) 
	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,

arch/x86/kernel/cpu/perf_event.h

+8 −0
Original line number Diff line number Diff line
@@ -307,6 +307,14 @@ struct x86_pmu { 
	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);

include/linux/perf_event.h

+1 −0
Original line number Diff line number Diff line
@@ -615,6 +615,7 @@ struct pmu { 
	struct list_head		entry;



	struct device			*dev;

	const struct attribute_group	**attr_groups;

	char				*name;

	int				type;

kernel/events/core.c

+1 −0
Original line number Diff line number Diff line
@@ -5505,6 +5505,7 @@ static int pmu_dev_alloc(struct pmu *pmu) 
	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)