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

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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: James Morse <james.morse@arm.com>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240529133446.28446-20-Jonathan.Cameron@huawei.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
James Morse 2024-05-29 14:34:46 +01:00 committed by Catalin Marinas
parent 828ce929d1
commit 4e1a7df454
4 changed files with 44 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

6
Documentation/ABI/testing/sysfs-devices-system-cpu
View file

@ -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.

10
drivers/base/cpu.c
View file

@ -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,

25
include/linux/cpumask.h
View file

@ -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;

3
kernel/cpu.c
View file

@ -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);