| Message ID | 20200128022737.15371-11-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, Jan 28, 2020 at 7:58 AM Atish Patra <atish.patra@wdc.com> 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. > > --------------------------------------------------- > 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> > --- > arch/riscv/Kconfig | 12 ++++- > arch/riscv/include/asm/cpu_ops.h | 5 ++ > arch/riscv/include/asm/smp.h | 7 +++ > arch/riscv/kernel/Makefile | 1 + > arch/riscv/kernel/cpu-hotplug.c | 84 ++++++++++++++++++++++++++++++++ > arch/riscv/kernel/cpu_ops.c | 34 +++++++++++++ > arch/riscv/kernel/setup.c | 26 ++++++++++ > 7 files changed, 168 insertions(+), 1 deletion(-) > create mode 100644 arch/riscv/kernel/cpu-hotplug.c > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 518da42be545..99fb481dc805 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -22,7 +22,6 @@ 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 > @@ -247,6 +246,17 @@ 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 27e9dfee5460..d53d7086f627 100644 > --- a/arch/riscv/include/asm/cpu_ops.h > +++ b/arch/riscv/include/asm/cpu_ops.h > @@ -23,6 +23,11 @@ struct cpu_operations { > 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..8d9c50c0f91c 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) > diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile > index d77def5b4e87..6fe35a719de1 100644 > --- a/arch/riscv/kernel/Makefile > +++ b/arch/riscv/kernel/Makefile > @@ -43,5 +43,6 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.o > obj-$(CONFIG_PERF_EVENTS) += perf_callchain.o > obj-$(CONFIG_HAVE_PERF_REGS) += perf_regs.o > obj-$(CONFIG_RISCV_SBI) += sbi.o > +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..835b0747803e > --- /dev/null > +++ b/arch/riscv/kernel/cpu-hotplug.c > @@ -0,0 +1,84 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2018 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); > +bool can_hotplug_cpu(void) > +{ > + return true; > +} > + > +void arch_cpu_idle_dead(void) > +{ > + cpu_stop(); > +} > + > +/* > + * __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.c b/arch/riscv/kernel/cpu_ops.c > index 454df032066f..9b315137b945 100644 > --- a/arch/riscv/kernel/cpu_ops.c > +++ b/arch/riscv/kernel/cpu_ops.c > @@ -59,6 +59,34 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle) > return rc; > } > > +#ifdef CONFIG_HOTPLUG_CPU > +static int sbi_cpu_disable(unsigned int cpuid) > +{ > + if (!cpu_sbi_ops.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 == RISCV_HART_FIRMWARE_STOPPED) > + return 0; > + return rc; > +} > +#endif > static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle) > { > int hartid = cpuid_to_hartid_map(cpuid); > @@ -82,6 +110,11 @@ const struct cpu_operations cpu_sbi_ops = { > .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 > }; > > const struct cpu_operations cpu_spinwait_ops = { > @@ -90,6 +123,7 @@ const struct cpu_operations cpu_spinwait_ops = { > .cpu_start = spinwait_cpu_start, > }; > > + > int __init cpu_set_ops(int cpuid) > { > if (sbi_hsm_is_available()) > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index 8208d1109ddb..dfab3bd40f2a 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -43,6 +43,7 @@ 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 +91,28 @@ void __init setup_arch(char **cmdline_p) > > riscv_fill_hwcap(); > } > + > +static inline bool can_hotplug_cpu(unsigned int cpu) > +{ > +#ifdef CONFIG_HOTPLUG_CPU > + if (cpu_ops[cpu]->cpu_stop) > + return true; > +#endif > + return false; > +} > + > +static int __init topology_init(void) > +{ > + int i; > + > + pr_err("%s: In\n", __func__); Remove this pr_err() > + for_each_possible_cpu(i) { > + struct cpu *cpu = &per_cpu(cpu_devices, i); > + > + cpu->hotpluggable = can_hotplug_cpu(i); > + register_cpu(cpu, i); > + } > + > + return 0; > +} > +subsys_initcall(topology_init); > -- > 2.24.0 > Regards, Anup
On Mon, Jan 27, 2020 at 9:01 PM Anup Patel <anup@brainfault.org> wrote: > > On Tue, Jan 28, 2020 at 7:58 AM Atish Patra <atish.patra@wdc.com> 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. > > > > --------------------------------------------------- > > 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> > > --- > > arch/riscv/Kconfig | 12 ++++- > > arch/riscv/include/asm/cpu_ops.h | 5 ++ > > arch/riscv/include/asm/smp.h | 7 +++ > > arch/riscv/kernel/Makefile | 1 + > > arch/riscv/kernel/cpu-hotplug.c | 84 ++++++++++++++++++++++++++++++++ > > arch/riscv/kernel/cpu_ops.c | 34 +++++++++++++ > > arch/riscv/kernel/setup.c | 26 ++++++++++ > > 7 files changed, 168 insertions(+), 1 deletion(-) > > create mode 100644 arch/riscv/kernel/cpu-hotplug.c > > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > index 518da42be545..99fb481dc805 100644 > > --- a/arch/riscv/Kconfig > > +++ b/arch/riscv/Kconfig > > @@ -22,7 +22,6 @@ 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 > > @@ -247,6 +246,17 @@ 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 27e9dfee5460..d53d7086f627 100644 > > --- a/arch/riscv/include/asm/cpu_ops.h > > +++ b/arch/riscv/include/asm/cpu_ops.h > > @@ -23,6 +23,11 @@ struct cpu_operations { > > 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..8d9c50c0f91c 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) > > diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile > > index d77def5b4e87..6fe35a719de1 100644 > > --- a/arch/riscv/kernel/Makefile > > +++ b/arch/riscv/kernel/Makefile > > @@ -43,5 +43,6 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.o > > obj-$(CONFIG_PERF_EVENTS) += perf_callchain.o > > obj-$(CONFIG_HAVE_PERF_REGS) += perf_regs.o > > obj-$(CONFIG_RISCV_SBI) += sbi.o > > +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..835b0747803e > > --- /dev/null > > +++ b/arch/riscv/kernel/cpu-hotplug.c > > @@ -0,0 +1,84 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * Copyright (C) 2018 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); > > +bool can_hotplug_cpu(void) > > +{ > > + return true; > > +} > > + > > +void arch_cpu_idle_dead(void) > > +{ > > + cpu_stop(); > > +} > > + > > +/* > > + * __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.c b/arch/riscv/kernel/cpu_ops.c > > index 454df032066f..9b315137b945 100644 > > --- a/arch/riscv/kernel/cpu_ops.c > > +++ b/arch/riscv/kernel/cpu_ops.c > > @@ -59,6 +59,34 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle) > > return rc; > > } > > > > +#ifdef CONFIG_HOTPLUG_CPU > > +static int sbi_cpu_disable(unsigned int cpuid) > > +{ > > + if (!cpu_sbi_ops.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 == RISCV_HART_FIRMWARE_STOPPED) > > + return 0; > > + return rc; > > +} > > +#endif > > static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle) > > { > > int hartid = cpuid_to_hartid_map(cpuid); > > @@ -82,6 +110,11 @@ const struct cpu_operations cpu_sbi_ops = { > > .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 > > }; > > > > const struct cpu_operations cpu_spinwait_ops = { > > @@ -90,6 +123,7 @@ const struct cpu_operations cpu_spinwait_ops = { > > .cpu_start = spinwait_cpu_start, > > }; > > > > + > > int __init cpu_set_ops(int cpuid) > > { > > if (sbi_hsm_is_available()) > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > > index 8208d1109ddb..dfab3bd40f2a 100644 > > --- a/arch/riscv/kernel/setup.c > > +++ b/arch/riscv/kernel/setup.c > > @@ -43,6 +43,7 @@ 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 +91,28 @@ void __init setup_arch(char **cmdline_p) > > > > riscv_fill_hwcap(); > > } > > + > > +static inline bool can_hotplug_cpu(unsigned int cpu) > > +{ > > +#ifdef CONFIG_HOTPLUG_CPU > > + if (cpu_ops[cpu]->cpu_stop) > > + return true; > > +#endif > > + return false; > > +} > > + > > +static int __init topology_init(void) > > +{ > > + int i; > > + > > + pr_err("%s: In\n", __func__); > > Remove this pr_err() > Oops. My bad. I forgot to remove this. > > + for_each_possible_cpu(i) { > > + struct cpu *cpu = &per_cpu(cpu_devices, i); > > + > > + cpu->hotpluggable = can_hotplug_cpu(i); > > + register_cpu(cpu, i); > > + } > > + > > + return 0; > > +} > > +subsys_initcall(topology_init); > > -- > > 2.24.0 > > > > Regards, > Anup >
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 518da42be545..99fb481dc805 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -22,7 +22,6 @@ 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 @@ -247,6 +246,17 @@ 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 27e9dfee5460..d53d7086f627 100644 --- a/arch/riscv/include/asm/cpu_ops.h +++ b/arch/riscv/include/asm/cpu_ops.h @@ -23,6 +23,11 @@ struct cpu_operations { 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..8d9c50c0f91c 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) diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index d77def5b4e87..6fe35a719de1 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -43,5 +43,6 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.o obj-$(CONFIG_PERF_EVENTS) += perf_callchain.o obj-$(CONFIG_HAVE_PERF_REGS) += perf_regs.o obj-$(CONFIG_RISCV_SBI) += sbi.o +obj-$(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..835b0747803e --- /dev/null +++ b/arch/riscv/kernel/cpu-hotplug.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2018 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); +bool can_hotplug_cpu(void) +{ + return true; +} + +void arch_cpu_idle_dead(void) +{ + cpu_stop(); +} + +/* + * __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.c b/arch/riscv/kernel/cpu_ops.c index 454df032066f..9b315137b945 100644 --- a/arch/riscv/kernel/cpu_ops.c +++ b/arch/riscv/kernel/cpu_ops.c @@ -59,6 +59,34 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle) return rc; } +#ifdef CONFIG_HOTPLUG_CPU +static int sbi_cpu_disable(unsigned int cpuid) +{ + if (!cpu_sbi_ops.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 == RISCV_HART_FIRMWARE_STOPPED) + return 0; + return rc; +} +#endif static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle) { int hartid = cpuid_to_hartid_map(cpuid); @@ -82,6 +110,11 @@ const struct cpu_operations cpu_sbi_ops = { .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 }; const struct cpu_operations cpu_spinwait_ops = { @@ -90,6 +123,7 @@ const struct cpu_operations cpu_spinwait_ops = { .cpu_start = spinwait_cpu_start, }; + int __init cpu_set_ops(int cpuid) { if (sbi_hsm_is_available()) diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c index 8208d1109ddb..dfab3bd40f2a 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -43,6 +43,7 @@ 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 +91,28 @@ void __init setup_arch(char **cmdline_p) riscv_fill_hwcap(); } + +static inline bool can_hotplug_cpu(unsigned int cpu) +{ +#ifdef CONFIG_HOTPLUG_CPU + if (cpu_ops[cpu]->cpu_stop) + return true; +#endif + return false; +} + +static int __init topology_init(void) +{ + int i; + + pr_err("%s: In\n", __func__); + for_each_possible_cpu(i) { + struct cpu *cpu = &per_cpu(cpu_devices, i); + + cpu->hotpluggable = can_hotplug_cpu(i); + register_cpu(cpu, i); + } + + return 0; +} +subsys_initcall(topology_init);
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. --------------------------------------------------- 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> --- arch/riscv/Kconfig | 12 ++++- arch/riscv/include/asm/cpu_ops.h | 5 ++ arch/riscv/include/asm/smp.h | 7 +++ arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/cpu-hotplug.c | 84 ++++++++++++++++++++++++++++++++ arch/riscv/kernel/cpu_ops.c | 34 +++++++++++++ arch/riscv/kernel/setup.c | 26 ++++++++++ 7 files changed, 168 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/kernel/cpu-hotplug.c