| Message ID | 20200318011144.91532-12-atish.patra@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add support for SBI v0.2 and CPU hotplug | expand |
On Tue, 17 Mar 2020 18:11:44 PDT (-0700), Atish Patra wrote: > This patch enable support for cpu hotplug in RISC-V. It uses SBI HSM > extension to online/offline any hart. As a result, the harts are > returned to firmware once they are offline. If the harts are brought > online afterwards, they re-enter Linux kernel as if a secondary hart > booted for the first time. All booting requirements are honored during > this process. > > Tested both on QEMU and HighFive Unleashed board with. Test result follows. I had to jump through some hoops to apply this one on for-next. It should be f1e58583b9c7 ("RISC-V: Support cpu hotplug") now, LMK if something went wrong. > > --------------------------------------------------- > Offline cpu 2 > --------------------------------------------------- > $ echo 0 > /sys/devices/system/cpu/cpu2/online > [ 32.828684] CPU2: off > $ cat /proc/cpuinfo > processor : 0 > hart : 0 > isa : rv64imafdcsu > mmu : sv48 > > processor : 1 > hart : 1 > isa : rv64imafdcsu > mmu : sv48 > > processor : 3 > hart : 3 > isa : rv64imafdcsu > mmu : sv48 > > processor : 4 > hart : 4 > isa : rv64imafdcsu > mmu : sv48 > > processor : 5 > hart : 5 > isa : rv64imafdcsu > mmu : sv48 > > processor : 6 > hart : 6 > isa : rv64imafdcsu > mmu : sv48 > > processor : 7 > hart : 7 > isa : rv64imafdcsu > mmu : sv48 > > --------------------------------------------------- > online cpu 2 > --------------------------------------------------- > $ echo 1 > /sys/devices/system/cpu/cpu2/online > $ cat /proc/cpuinfo > processor : 0 > hart : 0 > isa : rv64imafdcsu > mmu : sv48 > > processor : 1 > hart : 1 > isa : rv64imafdcsu > mmu : sv48 > > processor : 2 > hart : 2 > isa : rv64imafdcsu > mmu : sv48 > > processor : 3 > hart : 3 > isa : rv64imafdcsu > mmu : sv48 > > processor : 4 > hart : 4 > isa : rv64imafdcsu > mmu : sv48 > > processor : 5 > hart : 5 > isa : rv64imafdcsu > mmu : sv48 > > processor : 6 > hart : 6 > isa : rv64imafdcsu > mmu : sv48 > > processor : 7 > hart : 7 > isa : rv64imafdcsu > mmu : sv48 > > Signed-off-by: Atish Patra <atish.patra@wdc.com> > Reviewed-by: Anup Patel <anup@brainfault.org> > --- > arch/riscv/Kconfig | 12 ++++- > arch/riscv/include/asm/cpu_ops.h | 12 +++++ > arch/riscv/include/asm/smp.h | 17 +++++++ > arch/riscv/kernel/Makefile | 1 + > arch/riscv/kernel/cpu-hotplug.c | 87 ++++++++++++++++++++++++++++++++ > arch/riscv/kernel/cpu_ops_sbi.c | 34 +++++++++++++ > arch/riscv/kernel/setup.c | 19 ++++++- > 7 files changed, 180 insertions(+), 2 deletions(-) > create mode 100644 arch/riscv/kernel/cpu-hotplug.c > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 20c6191399ea..b3daadd116ec 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -20,7 +20,6 @@ config RISCV > select CLONE_BACKWARDS > select COMMON_CLK > select GENERIC_CLOCKEVENTS > - select GENERIC_CPU_DEVICES > select GENERIC_IRQ_SHOW > select GENERIC_PCI_IOMAP > select GENERIC_SCHED_CLOCK > @@ -248,6 +247,17 @@ config NR_CPUS > depends on SMP > default "8" > > +config HOTPLUG_CPU > + bool "Support for hot-pluggable CPUs" > + depends on SMP > + select GENERIC_IRQ_MIGRATION > + help > + > + Say Y here to experiment with turning CPUs off and on. CPUs > + can be controlled through /sys/devices/system/cpu. > + > + Say N if you want to disable CPU hotplug. > + > choice > prompt "CPU Tuning" > default TUNE_GENERIC > diff --git a/arch/riscv/include/asm/cpu_ops.h b/arch/riscv/include/asm/cpu_ops.h > index 5ce81a28e1d9..a8ec3c5c1bd2 100644 > --- a/arch/riscv/include/asm/cpu_ops.h > +++ b/arch/riscv/include/asm/cpu_ops.h > @@ -18,12 +18,24 @@ > * is a mechanism for doing so, tests whether it is > * possible to boot the given HART. > * @cpu_start: Boots a cpu into the kernel. > + * @cpu_disable: Prepares a cpu to die. May fail for some > + * mechanism-specific reason, which will cause the hot > + * unplug to be aborted. Called from the cpu to be killed. > + * @cpu_stop: Makes a cpu leave the kernel. Must not fail. Called from > + * the cpu being stopped. > + * @cpu_is_stopped: Ensures a cpu has left the kernel. Called from another > + * cpu. > */ > struct cpu_operations { > const char *name; > int (*cpu_prepare)(unsigned int cpu); > int (*cpu_start)(unsigned int cpu, > struct task_struct *tidle); > +#ifdef CONFIG_HOTPLUG_CPU > + int (*cpu_disable)(unsigned int cpu); > + void (*cpu_stop)(void); > + int (*cpu_is_stopped)(unsigned int cpu); > +#endif > }; > > extern const struct cpu_operations *cpu_ops[NR_CPUS]; > diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h > index 023f74fb8b3b..f4c7cfda6b7f 100644 > --- a/arch/riscv/include/asm/smp.h > +++ b/arch/riscv/include/asm/smp.h > @@ -43,6 +43,13 @@ void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out); > */ > #define raw_smp_processor_id() (current_thread_info()->cpu) > > +#if defined CONFIG_HOTPLUG_CPU > +int __cpu_disable(void); > +void __cpu_die(unsigned int cpu); > +void cpu_stop(void); > +#else > +#endif /* CONFIG_HOTPLUG_CPU */ > + > #else > > static inline void show_ipi_stats(struct seq_file *p, int prec) > @@ -69,4 +76,14 @@ static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in, > } > > #endif /* CONFIG_SMP */ > + > +#if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP) > +bool cpu_has_hotplug(unsigned int cpu); > +#else > +static inline bool cpu_has_hotplug(unsigned int cpu) > +{ > + return false; > +} > +#endif > + > #endif /* _ASM_RISCV_SMP_H */ > diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile > index a0be34b96846..9601ac907f70 100644 > --- a/arch/riscv/kernel/Makefile > +++ b/arch/riscv/kernel/Makefile > @@ -47,5 +47,6 @@ obj-$(CONFIG_RISCV_SBI) += sbi.o > ifeq ($(CONFIG_RISCV_SBI), y) > obj-$(CONFIG_SMP) += cpu_ops_sbi.o > endif > +obj-$(CONFIG_HOTPLUG_CPU) += cpu-hotplug.o > > clean: > diff --git a/arch/riscv/kernel/cpu-hotplug.c b/arch/riscv/kernel/cpu-hotplug.c > new file mode 100644 > index 000000000000..df84e0c13db1 > --- /dev/null > +++ b/arch/riscv/kernel/cpu-hotplug.c > @@ -0,0 +1,87 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2020 Western Digital Corporation or its affiliates. > + */ > + > +#include <linux/kernel.h> > +#include <linux/mm.h> > +#include <linux/sched.h> > +#include <linux/err.h> > +#include <linux/irq.h> > +#include <linux/cpu.h> > +#include <linux/sched/hotplug.h> > +#include <asm/irq.h> > +#include <asm/cpu_ops.h> > +#include <asm/sbi.h> > + > +void cpu_stop(void); > +void arch_cpu_idle_dead(void) > +{ > + cpu_stop(); > +} > + > +bool cpu_has_hotplug(unsigned int cpu) > +{ > + if (cpu_ops[cpu]->cpu_stop) > + return true; > + > + return false; > +} > + > +/* > + * __cpu_disable runs on the processor to be shutdown. > + */ > +int __cpu_disable(void) > +{ > + int ret = 0; > + unsigned int cpu = smp_processor_id(); > + > + if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_stop) > + return -EOPNOTSUPP; > + > + if (cpu_ops[cpu]->cpu_disable) > + ret = cpu_ops[cpu]->cpu_disable(cpu); > + > + if (ret) > + return ret; > + > + remove_cpu_topology(cpu); > + set_cpu_online(cpu, false); > + irq_migrate_all_off_this_cpu(); > + > + return ret; > +} > + > +/* > + * Called on the thread which is asking for a CPU to be shutdown. > + */ > +void __cpu_die(unsigned int cpu) > +{ > + int ret = 0; > + > + if (!cpu_wait_death(cpu, 5)) { > + pr_err("CPU %u: didn't die\n", cpu); > + return; > + } > + pr_notice("CPU%u: off\n", cpu); > + > + /* Verify from the firmware if the cpu is really stopped*/ > + if (cpu_ops[cpu]->cpu_is_stopped) > + ret = cpu_ops[cpu]->cpu_is_stopped(cpu); > + if (ret) > + pr_warn("CPU%d may not have stopped: %d\n", cpu, ret); > +} > + > +/* > + * Called from the idle thread for the CPU which has been shutdown. > + */ > +void cpu_stop(void) > +{ > + idle_task_exit(); > + > + (void)cpu_report_death(); > + > + cpu_ops[smp_processor_id()]->cpu_stop(); > + /* It should never reach here */ > + BUG(); > +} > diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c > index 66f3cded91f5..685fae72b7f5 100644 > --- a/arch/riscv/kernel/cpu_ops_sbi.c > +++ b/arch/riscv/kernel/cpu_ops_sbi.c > @@ -74,8 +74,42 @@ static int sbi_cpu_prepare(unsigned int cpuid) > return 0; > } > > +#ifdef CONFIG_HOTPLUG_CPU > +static int sbi_cpu_disable(unsigned int cpuid) > +{ > + if (!cpu_ops_sbi.cpu_stop) > + return -EOPNOTSUPP; > + return 0; > +} > + > +static void sbi_cpu_stop(void) > +{ > + int ret; > + > + ret = sbi_hsm_hart_stop(); > + pr_crit("Unable to stop the cpu %u (%d)\n", smp_processor_id(), ret); > +} > + > +static int sbi_cpu_is_stopped(unsigned int cpuid) > +{ > + int rc; > + int hartid = cpuid_to_hartid_map(cpuid); > + > + rc = sbi_hsm_hart_get_status(hartid); > + > + if (rc == SBI_HSM_HART_STATUS_STOPPED) > + return 0; > + return rc; > +} > +#endif > + > const struct cpu_operations cpu_ops_sbi = { > .name = "sbi", > .cpu_prepare = sbi_cpu_prepare, > .cpu_start = sbi_cpu_start, > +#ifdef CONFIG_HOTPLUG_CPU > + .cpu_disable = sbi_cpu_disable, > + .cpu_stop = sbi_cpu_stop, > + .cpu_is_stopped = sbi_cpu_is_stopped, > +#endif > }; > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index 44ac4ddf60ab..1d2f66579b94 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -16,12 +16,13 @@ > #include <linux/of_platform.h> > #include <linux/sched/task.h> > #include <linux/swiotlb.h> > +#include <linux/smp.h> > > #include <asm/clint.h> > +#include <asm/cpu_ops.h> > #include <asm/setup.h> > #include <asm/sections.h> > #include <asm/pgtable.h> > -#include <asm/smp.h> > #include <asm/sbi.h> > #include <asm/tlbflush.h> > #include <asm/thread_info.h> > @@ -43,6 +44,7 @@ struct screen_info screen_info = { > /* The lucky hart to first increment this variable will boot the other cores */ > atomic_t hart_lottery; > unsigned long boot_cpu_hartid; > +static DEFINE_PER_CPU(struct cpu, cpu_devices); > > void __init parse_dtb(void) > { > @@ -90,3 +92,18 @@ void __init setup_arch(char **cmdline_p) > > riscv_fill_hwcap(); > } > + > +static int __init topology_init(void) > +{ > + int i; > + > + for_each_possible_cpu(i) { > + struct cpu *cpu = &per_cpu(cpu_devices, i); > + > + cpu->hotpluggable = cpu_has_hotplug(i); > + register_cpu(cpu, i); > + } > + > + return 0; > +} > +subsys_initcall(topology_init);
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 20c6191399ea..b3daadd116ec 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -20,7 +20,6 @@ config RISCV select CLONE_BACKWARDS select COMMON_CLK select GENERIC_CLOCKEVENTS - select GENERIC_CPU_DEVICES select GENERIC_IRQ_SHOW select GENERIC_PCI_IOMAP select GENERIC_SCHED_CLOCK @@ -248,6 +247,17 @@ config NR_CPUS depends on SMP default "8" +config HOTPLUG_CPU + bool "Support for hot-pluggable CPUs" + depends on SMP + select GENERIC_IRQ_MIGRATION + help + + Say Y here to experiment with turning CPUs off and on. CPUs + can be controlled through /sys/devices/system/cpu. + + Say N if you want to disable CPU hotplug. + choice prompt "CPU Tuning" default TUNE_GENERIC diff --git a/arch/riscv/include/asm/cpu_ops.h b/arch/riscv/include/asm/cpu_ops.h index 5ce81a28e1d9..a8ec3c5c1bd2 100644 --- a/arch/riscv/include/asm/cpu_ops.h +++ b/arch/riscv/include/asm/cpu_ops.h @@ -18,12 +18,24 @@ * is a mechanism for doing so, tests whether it is * possible to boot the given HART. * @cpu_start: Boots a cpu into the kernel. + * @cpu_disable: Prepares a cpu to die. May fail for some + * mechanism-specific reason, which will cause the hot + * unplug to be aborted. Called from the cpu to be killed. + * @cpu_stop: Makes a cpu leave the kernel. Must not fail. Called from + * the cpu being stopped. + * @cpu_is_stopped: Ensures a cpu has left the kernel. Called from another + * cpu. */ struct cpu_operations { const char *name; int (*cpu_prepare)(unsigned int cpu); int (*cpu_start)(unsigned int cpu, struct task_struct *tidle); +#ifdef CONFIG_HOTPLUG_CPU + int (*cpu_disable)(unsigned int cpu); + void (*cpu_stop)(void); + int (*cpu_is_stopped)(unsigned int cpu); +#endif }; extern const struct cpu_operations *cpu_ops[NR_CPUS]; diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h index 023f74fb8b3b..f4c7cfda6b7f 100644 --- a/arch/riscv/include/asm/smp.h +++ b/arch/riscv/include/asm/smp.h @@ -43,6 +43,13 @@ void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out); */ #define raw_smp_processor_id() (current_thread_info()->cpu) +#if defined CONFIG_HOTPLUG_CPU +int __cpu_disable(void); +void __cpu_die(unsigned int cpu); +void cpu_stop(void); +#else +#endif /* CONFIG_HOTPLUG_CPU */ + #else static inline void show_ipi_stats(struct seq_file *p, int prec) @@ -69,4 +76,14 @@ static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in, } #endif /* CONFIG_SMP */ + +#if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP) +bool cpu_has_hotplug(unsigned int cpu); +#else +static inline bool cpu_has_hotplug(unsigned int cpu) +{ + return false; +} +#endif + #endif /* _ASM_RISCV_SMP_H */ diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index a0be34b96846..9601ac907f70 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -47,5 +47,6 @@ obj-$(CONFIG_RISCV_SBI) += sbi.o ifeq ($(CONFIG_RISCV_SBI), y) obj-$(CONFIG_SMP) += cpu_ops_sbi.o endif +obj-$(CONFIG_HOTPLUG_CPU) += cpu-hotplug.o clean: diff --git a/arch/riscv/kernel/cpu-hotplug.c b/arch/riscv/kernel/cpu-hotplug.c new file mode 100644 index 000000000000..df84e0c13db1 --- /dev/null +++ b/arch/riscv/kernel/cpu-hotplug.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2020 Western Digital Corporation or its affiliates. + */ + +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/sched.h> +#include <linux/err.h> +#include <linux/irq.h> +#include <linux/cpu.h> +#include <linux/sched/hotplug.h> +#include <asm/irq.h> +#include <asm/cpu_ops.h> +#include <asm/sbi.h> + +void cpu_stop(void); +void arch_cpu_idle_dead(void) +{ + cpu_stop(); +} + +bool cpu_has_hotplug(unsigned int cpu) +{ + if (cpu_ops[cpu]->cpu_stop) + return true; + + return false; +} + +/* + * __cpu_disable runs on the processor to be shutdown. + */ +int __cpu_disable(void) +{ + int ret = 0; + unsigned int cpu = smp_processor_id(); + + if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_stop) + return -EOPNOTSUPP; + + if (cpu_ops[cpu]->cpu_disable) + ret = cpu_ops[cpu]->cpu_disable(cpu); + + if (ret) + return ret; + + remove_cpu_topology(cpu); + set_cpu_online(cpu, false); + irq_migrate_all_off_this_cpu(); + + return ret; +} + +/* + * Called on the thread which is asking for a CPU to be shutdown. + */ +void __cpu_die(unsigned int cpu) +{ + int ret = 0; + + if (!cpu_wait_death(cpu, 5)) { + pr_err("CPU %u: didn't die\n", cpu); + return; + } + pr_notice("CPU%u: off\n", cpu); + + /* Verify from the firmware if the cpu is really stopped*/ + if (cpu_ops[cpu]->cpu_is_stopped) + ret = cpu_ops[cpu]->cpu_is_stopped(cpu); + if (ret) + pr_warn("CPU%d may not have stopped: %d\n", cpu, ret); +} + +/* + * Called from the idle thread for the CPU which has been shutdown. + */ +void cpu_stop(void) +{ + idle_task_exit(); + + (void)cpu_report_death(); + + cpu_ops[smp_processor_id()]->cpu_stop(); + /* It should never reach here */ + BUG(); +} diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c index 66f3cded91f5..685fae72b7f5 100644 --- a/arch/riscv/kernel/cpu_ops_sbi.c +++ b/arch/riscv/kernel/cpu_ops_sbi.c @@ -74,8 +74,42 @@ static int sbi_cpu_prepare(unsigned int cpuid) return 0; } +#ifdef CONFIG_HOTPLUG_CPU +static int sbi_cpu_disable(unsigned int cpuid) +{ + if (!cpu_ops_sbi.cpu_stop) + return -EOPNOTSUPP; + return 0; +} + +static void sbi_cpu_stop(void) +{ + int ret; + + ret = sbi_hsm_hart_stop(); + pr_crit("Unable to stop the cpu %u (%d)\n", smp_processor_id(), ret); +} + +static int sbi_cpu_is_stopped(unsigned int cpuid) +{ + int rc; + int hartid = cpuid_to_hartid_map(cpuid); + + rc = sbi_hsm_hart_get_status(hartid); + + if (rc == SBI_HSM_HART_STATUS_STOPPED) + return 0; + return rc; +} +#endif + const struct cpu_operations cpu_ops_sbi = { .name = "sbi", .cpu_prepare = sbi_cpu_prepare, .cpu_start = sbi_cpu_start, +#ifdef CONFIG_HOTPLUG_CPU + .cpu_disable = sbi_cpu_disable, + .cpu_stop = sbi_cpu_stop, + .cpu_is_stopped = sbi_cpu_is_stopped, +#endif }; diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c index 44ac4ddf60ab..1d2f66579b94 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -16,12 +16,13 @@ #include <linux/of_platform.h> #include <linux/sched/task.h> #include <linux/swiotlb.h> +#include <linux/smp.h> #include <asm/clint.h> +#include <asm/cpu_ops.h> #include <asm/setup.h> #include <asm/sections.h> #include <asm/pgtable.h> -#include <asm/smp.h> #include <asm/sbi.h> #include <asm/tlbflush.h> #include <asm/thread_info.h> @@ -43,6 +44,7 @@ struct screen_info screen_info = { /* The lucky hart to first increment this variable will boot the other cores */ atomic_t hart_lottery; unsigned long boot_cpu_hartid; +static DEFINE_PER_CPU(struct cpu, cpu_devices); void __init parse_dtb(void) { @@ -90,3 +92,18 @@ void __init setup_arch(char **cmdline_p) riscv_fill_hwcap(); } + +static int __init topology_init(void) +{ + int i; + + for_each_possible_cpu(i) { + struct cpu *cpu = &per_cpu(cpu_devices, i); + + cpu->hotpluggable = cpu_has_hotplug(i); + register_cpu(cpu, i); + } + + return 0; +} +subsys_initcall(topology_init);