Commit de7b77e5 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Thomas Gleixner
Browse files

cpu/hotplug: Create SMT sysfs interface for all arches 



Make the /sys/devices/system/cpu/smt/* files available on all arches, so
user space has a consistent way to detect whether SMT is enabled.

The 'control' file now shows 'notimplemented' for architectures which
don't yet have CONFIG_HOTPLUG_SMT.

[ tglx: Make notimplemented a real state ]

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jikos@kernel.org>
Link: https://lkml.kernel.org/r/469c2b98055f2c41e75748e06447d592a64080c9.1553635520.git.jpoimboe@redhat.com
parent 79a3aaa7

Documentation/ABI/testing/sysfs-devices-system-cpu

+6 −4
Original line number Diff line number Diff line
@@ -515,6 +515,8 @@ Description: Control Symetric Multi Threading (SMT) 
			 "off"		  SMT is disabled

			 "forceoff"	  SMT is force disabled. Cannot be changed.

			 "notsupported"   SMT is not supported by the CPU

			 "notimplemented" SMT runtime toggling is not

					  implemented for the architecture



			 If control status is "forceoff" or "notsupported" writes

			 are rejected.

include/linux/cpu.h

+2 −1
Original line number Diff line number Diff line
@@ -175,6 +175,7 @@ enum cpuhp_smt_control { 
	CPU_SMT_DISABLED,

	CPU_SMT_FORCE_DISABLED,

	CPU_SMT_NOT_SUPPORTED,

	CPU_SMT_NOT_IMPLEMENTED,

};



#if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT)
@@ -182,7 +183,7 @@ extern enum cpuhp_smt_control cpu_smt_control; 
extern void cpu_smt_disable(bool force);

extern void cpu_smt_check_topology(void);

#else

# define cpu_smt_control		(CPU_SMT_ENABLED)

# define cpu_smt_control		(CPU_SMT_NOT_IMPLEMENTED)

static inline void cpu_smt_disable(bool force) { }

static inline void cpu_smt_check_topology(void) { }

#endif

kernel/cpu.c

+39 −25
Original line number Diff line number Diff line
@@ -2033,19 +2033,6 @@ static const struct attribute_group cpuhp_cpu_root_attr_group = { 


#ifdef CONFIG_HOTPLUG_SMT



static const char *smt_states[] = {

	[CPU_SMT_ENABLED]		= "on",

	[CPU_SMT_DISABLED]		= "off",

	[CPU_SMT_FORCE_DISABLED]	= "forceoff",

	[CPU_SMT_NOT_SUPPORTED]		= "notsupported",

};



static ssize_t

show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)

{

	return snprintf(buf, PAGE_SIZE - 2, "%s\n", smt_states[cpu_smt_control]);

}



static void cpuhp_offline_cpu_device(unsigned int cpu)

{

	struct device *dev = get_cpu_device(cpu);
@@ -2116,8 +2103,9 @@ static int cpuhp_smt_enable(void) 
	return ret;

}





static ssize_t

store_smt_control(struct device *dev, struct device_attribute *attr,

__store_smt_control(struct device *dev, struct device_attribute *attr,

		    const char *buf, size_t count)

{

	int ctrlval, ret;
@@ -2156,14 +2144,44 @@ store_smt_control(struct device *dev, struct device_attribute *attr, 
	unlock_device_hotplug();

	return ret ? ret : count;

}



#else /* !CONFIG_HOTPLUG_SMT */

static ssize_t

__store_smt_control(struct device *dev, struct device_attribute *attr,

		    const char *buf, size_t count)

{

	return -ENODEV;

}

#endif /* CONFIG_HOTPLUG_SMT */



static const char *smt_states[] = {

	[CPU_SMT_ENABLED]		= "on",

	[CPU_SMT_DISABLED]		= "off",

	[CPU_SMT_FORCE_DISABLED]	= "forceoff",

	[CPU_SMT_NOT_SUPPORTED]		= "notsupported",

	[CPU_SMT_NOT_IMPLEMENTED]	= "notimplemented",

};



static ssize_t

show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)

{

	const char *state = smt_states[cpu_smt_control];



	return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);

}



static ssize_t

store_smt_control(struct device *dev, struct device_attribute *attr,

		  const char *buf, size_t count)

{

	return __store_smt_control(dev, attr, buf, count);

}

static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);



static ssize_t

show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)

{

	bool active = topology_max_smt_threads() > 1;



	return snprintf(buf, PAGE_SIZE - 2, "%d\n", active);

	return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());

}

static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
@@ -2179,21 +2197,17 @@ static const struct attribute_group cpuhp_smt_attr_group = { 
	NULL

};



static int __init cpu_smt_state_init(void)

static int __init cpu_smt_sysfs_init(void)

{

	return sysfs_create_group(&cpu_subsys.dev_root->kobj,

				  &cpuhp_smt_attr_group);

}



#else

static inline int cpu_smt_state_init(void) { return 0; }

#endif



static int __init cpuhp_sysfs_init(void)

{

	int cpu, ret;



	ret = cpu_smt_state_init();

	ret = cpu_smt_sysfs_init();

	if (ret)

		return ret;
@@ -2214,7 +2228,7 @@ static int __init cpuhp_sysfs_init(void) 
	return 0;

}

device_initcall(cpuhp_sysfs_init);

#endif

#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */



/*

 * cpu_bit_bitmap[] is a special, "compressed" data structure that

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