From f1e58583b9c7ceae7f11646e9edf2561d67f29c9 Mon Sep 17 00:00:00 2001 From: Atish Patra Date: Tue, 17 Mar 2020 18:11:44 -0700 Subject: RISC-V: Support cpu hotplug 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 Reviewed-by: Anup Patel --- 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 ++++++++- 4 files changed, 140 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/kernel/cpu-hotplug.c (limited to 'arch/riscv/kernel') diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index 674a23cc4223..c121cc491eb8 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -49,5 +49,6 @@ 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include + +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 07f4e7503223..145128a7e560 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -16,12 +16,13 @@ #include #include #include +#include #include +#include #include #include #include -#include #include #include #include @@ -47,6 +48,7 @@ struct screen_info screen_info = { */ atomic_t hart_lottery __section(.sdata); unsigned long boot_cpu_hartid; +static DEFINE_PER_CPU(struct cpu, cpu_devices); void __init parse_dtb(void) { @@ -94,3 +96,18 @@ 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); -- cgit v1.2.3