Commit 4e1a7df4 authored by James Morse's avatar James Morse Committed by Catalin Marinas
Browse files

cpumask: Add enabled cpumask for present CPUs that can be brought online 



The 'offline' file in sysfs shows all offline CPUs, including those
that aren't present. User-space is expected to remove not-present CPUs
from this list to learn which CPUs could be brought online.

CPUs can be present but not-enabled. These CPUs can't be brought online
until the firmware policy changes, which comes with an ACPI notification
that will register the CPUs.

With only the offline and present files, user-space is unable to
determine which CPUs it can try to bring online. Add a new CPU mask
that shows this based on all the registered CPUs.

Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Tested-by: default avatarMiguel Luis <miguel.luis@oracle.com>
Tested-by: default avatarVishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: default avatarJianyong Wu <jianyong.wu@arm.com>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: default avatarGavin Shan <gshan@redhat.com>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240529133446.28446-20-Jonathan.Cameron@huawei.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 828ce929

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

+6 −0
Original line number Diff line number Diff line
@@ -694,3 +694,9 @@ Description: 
		(RO) indicates whether or not the kernel directly supports

		modifying the crash elfcorehdr for CPU hot un/plug and/or

		on/offline changes.



What:		/sys/devices/system/cpu/enabled

Date:		Nov 2022

Contact:	Linux kernel mailing list <linux-kernel@vger.kernel.org>

Description:

		(RO) the list of CPUs that can be brought online.

drivers/base/cpu.c

+10 −0
Original line number Diff line number Diff line
@@ -95,6 +95,7 @@ void unregister_cpu(struct cpu *cpu) 
{

	int logical_cpu = cpu->dev.id;



	set_cpu_enabled(logical_cpu, false);

	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));



	device_unregister(&cpu->dev);
@@ -273,6 +274,13 @@ static ssize_t print_cpus_offline(struct device *dev, 
}

static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);



static ssize_t print_cpus_enabled(struct device *dev,

				  struct device_attribute *attr, char *buf)

{

	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(cpu_enabled_mask));

}

static DEVICE_ATTR(enabled, 0444, print_cpus_enabled, NULL);



static ssize_t print_cpus_isolated(struct device *dev,

				  struct device_attribute *attr, char *buf)

{
@@ -413,6 +421,7 @@ int register_cpu(struct cpu *cpu, int num) 
	register_cpu_under_node(num, cpu_to_node(num));

	dev_pm_qos_expose_latency_limit(&cpu->dev,

					PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);

	set_cpu_enabled(num, true);



	return 0;

}
@@ -494,6 +503,7 @@ static struct attribute *cpu_root_attrs[] = { 
	&cpu_attrs[2].attr.attr,

	&dev_attr_kernel_max.attr,

	&dev_attr_offline.attr,

	&dev_attr_enabled.attr,

	&dev_attr_isolated.attr,

#ifdef CONFIG_NO_HZ_FULL

	&dev_attr_nohz_full.attr,

include/linux/cpumask.h

+25 −0
Original line number Diff line number Diff line
@@ -93,6 +93,7 @@ static inline void set_nr_cpu_ids(unsigned int nr) 
 *

 *     cpu_possible_mask- has bit 'cpu' set iff cpu is populatable

 *     cpu_present_mask - has bit 'cpu' set iff cpu is populated

 *     cpu_enabled_mask  - has bit 'cpu' set iff cpu can be brought online

 *     cpu_online_mask  - has bit 'cpu' set iff cpu available to scheduler

 *     cpu_active_mask  - has bit 'cpu' set iff cpu available to migration

 *
@@ -125,11 +126,13 @@ static inline void set_nr_cpu_ids(unsigned int nr) 


extern struct cpumask __cpu_possible_mask;

extern struct cpumask __cpu_online_mask;

extern struct cpumask __cpu_enabled_mask;

extern struct cpumask __cpu_present_mask;

extern struct cpumask __cpu_active_mask;

extern struct cpumask __cpu_dying_mask;

#define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask)

#define cpu_online_mask   ((const struct cpumask *)&__cpu_online_mask)

#define cpu_enabled_mask   ((const struct cpumask *)&__cpu_enabled_mask)

#define cpu_present_mask  ((const struct cpumask *)&__cpu_present_mask)

#define cpu_active_mask   ((const struct cpumask *)&__cpu_active_mask)

#define cpu_dying_mask    ((const struct cpumask *)&__cpu_dying_mask)
@@ -1075,6 +1078,7 @@ extern const DECLARE_BITMAP(cpu_all_bits, NR_CPUS); 
#else

#define for_each_possible_cpu(cpu) for_each_cpu((cpu), cpu_possible_mask)

#define for_each_online_cpu(cpu)   for_each_cpu((cpu), cpu_online_mask)

#define for_each_enabled_cpu(cpu)   for_each_cpu((cpu), cpu_enabled_mask)

#define for_each_present_cpu(cpu)  for_each_cpu((cpu), cpu_present_mask)

#endif
@@ -1092,6 +1096,15 @@ set_cpu_possible(unsigned int cpu, bool possible) 
		cpumask_clear_cpu(cpu, &__cpu_possible_mask);

}



static inline void

set_cpu_enabled(unsigned int cpu, bool can_be_onlined)

{

	if (can_be_onlined)

		cpumask_set_cpu(cpu, &__cpu_enabled_mask);

	else

		cpumask_clear_cpu(cpu, &__cpu_enabled_mask);

}



static inline void

set_cpu_present(unsigned int cpu, bool present)

{
@@ -1173,6 +1186,7 @@ static __always_inline unsigned int num_online_cpus(void) 
	return raw_atomic_read(&__num_online_cpus);

}

#define num_possible_cpus()	cpumask_weight(cpu_possible_mask)

#define num_enabled_cpus()	cpumask_weight(cpu_enabled_mask)

#define num_present_cpus()	cpumask_weight(cpu_present_mask)

#define num_active_cpus()	cpumask_weight(cpu_active_mask)
@@ -1181,6 +1195,11 @@ static inline bool cpu_online(unsigned int cpu) 
	return cpumask_test_cpu(cpu, cpu_online_mask);

}



static inline bool cpu_enabled(unsigned int cpu)

{

	return cpumask_test_cpu(cpu, cpu_enabled_mask);

}



static inline bool cpu_possible(unsigned int cpu)

{

	return cpumask_test_cpu(cpu, cpu_possible_mask);
@@ -1205,6 +1224,7 @@ static inline bool cpu_dying(unsigned int cpu) 


#define num_online_cpus()	1U

#define num_possible_cpus()	1U

#define num_enabled_cpus()	1U

#define num_present_cpus()	1U

#define num_active_cpus()	1U
@@ -1218,6 +1238,11 @@ static inline bool cpu_possible(unsigned int cpu) 
	return cpu == 0;

}



static inline bool cpu_enabled(unsigned int cpu)

{

	return cpu == 0;

}



static inline bool cpu_present(unsigned int cpu)

{

	return cpu == 0;

kernel/cpu.c

+3 −0
Original line number Diff line number Diff line
@@ -3069,6 +3069,9 @@ EXPORT_SYMBOL(__cpu_possible_mask); 
struct cpumask __cpu_online_mask __read_mostly;

EXPORT_SYMBOL(__cpu_online_mask);



struct cpumask __cpu_enabled_mask __read_mostly;

EXPORT_SYMBOL(__cpu_enabled_mask);



struct cpumask __cpu_present_mask __read_mostly;

EXPORT_SYMBOL(__cpu_present_mask);