On Wed, 13 Dec 2023 12:50:59 +0000 Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> wrote: > From: James Morse <james.morse@xxxxxxx> > > 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@xxxxxxx> > Tested-by: Miguel Luis <miguel.luis@xxxxxxxxxx> > Tested-by: Vishnu Pajjuri <vishnu@xxxxxxxxxxxxxxxxxxxxxx> > Tested-by: Jianyong Wu <jianyong.wu@xxxxxxx> > --- Needs docs Documentation/ABI/testing/sysfs-devices-system-cpu seems to have the rest of the similar entries. > Outstanding comment: > https://lore.kernel.org/r/20230914175443.000038f6@xxxxxxxxxx Very fussy reviewer. I'd ignore him on this :) Code is fine. Thanks for taking this forwards. Maybe the end of this saga is close! Jonathan > --- > drivers/base/cpu.c | 10 ++++++++++ > include/linux/cpumask.h | 25 +++++++++++++++++++++++++ > kernel/cpu.c | 3 +++ > 3 files changed, 38 insertions(+) > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c > index 13d052bf13f4..a6e96a0a92b7 100644 > --- a/drivers/base/cpu.c > +++ b/drivers/base/cpu.c > @@ -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, > diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h > index cfb545841a2c..cc72a0887f04 100644 > --- a/include/linux/cpumask.h > +++ b/include/linux/cpumask.h > @@ -92,6 +92,7 @@ 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 > * > @@ -124,11 +125,13 @@ 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) > @@ -993,6 +996,7 @@ 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 > > @@ -1015,6 +1019,15 @@ 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) > { > @@ -1096,6 +1109,7 @@ 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) > > @@ -1104,6 +1118,11 @@ 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); > @@ -1128,6 +1147,7 @@ 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 > > @@ -1141,6 +1161,11 @@ 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; > diff --git a/kernel/cpu.c b/kernel/cpu.c > index a86972a91991..fe0a5189f8ae 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -3122,6 +3122,9 @@ 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); >
