Tested both on QEMU and HighFive Unleashed board with
4 cpus. Test result follows.
$ echo 0 > /sys/devices/system/cpu/cpu2/online
[ 31.828562] CPU2: shutdown
$ cat /proc/cpuinfo
hart : 0
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
hart : 1
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
hart : 3
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
$ echo 0 > /sys/devices/system/cpu/cpu3/online
[ 52.968495] CPU3: shutdown
$ cat /proc/cpuinfo
hart : 0
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
hart : 2
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
$ echo 1 > /sys/devices/system/cpu/cpu3/online
[ 64.298250] CPU3: online
$ cat /proc/cpuinfo
hart : 0
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
hart : 1
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
hart : 3
isa : rv64imafdc
mmu : sv39
uarch : sifive,rocket0
Signed-off-by: Atish Patra <atish.pa...@wdc.com>
---
arch/riscv/Kconfig | 12 ++++++-
arch/riscv/include/asm/irq.h | 1 +
arch/riscv/include/asm/smp.h | 28 ++++++++++++++++
arch/riscv/kernel/Makefile | 1 +
arch/riscv/kernel/cpu-hotplug.c | 72 +++++++++++++++++++++++++++++++++++++++++
arch/riscv/kernel/head.S | 13 ++++++++
arch/riscv/kernel/irq.c | 24 ++++++++++++++
arch/riscv/kernel/setup.c | 17 +++++++++-
arch/riscv/kernel/smp.c | 8 +----
arch/riscv/kernel/smpboot.c | 7 ++--
arch/riscv/kernel/traps.c | 6 ++--
11 files changed, 175 insertions(+), 14 deletions(-)
create mode 100644 arch/riscv/kernel/cpu-hotplug.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a3449802..ea2e617e 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -21,7 +21,6 @@ config RISCV
select COMMON_CLK
select DMA_DIRECT_OPS
select GENERIC_CLOCKEVENTS
- select GENERIC_CPU_DEVICES
select GENERIC_IRQ_SHOW
select GENERIC_PCI_IOMAP
select GENERIC_STRNCPY_FROM_USER
@@ -167,6 +166,17 @@ config SMP
If you don't know what to do here, say N.
+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.
+
config NR_CPUS
int "Maximum number of CPUs (2-32)"
range 2 32
diff --git a/arch/riscv/include/asm/irq.h b/arch/riscv/include/asm/irq.h
index 996b6fbe..a873a72d 100644
--- a/arch/riscv/include/asm/irq.h
+++ b/arch/riscv/include/asm/irq.h
@@ -19,6 +19,7 @@
void riscv_timer_interrupt(void);
void riscv_software_interrupt(void);
+void wait_for_software_interrupt(void);
#include <asm-generic/irq.h>
diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index fce312ce..8145b865 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -25,8 +25,29 @@
extern unsigned long __cpuid_to_hardid_map[NR_CPUS];
#define cpuid_to_hardid_map(cpu) __cpuid_to_hardid_map[cpu]
+#if defined CONFIG_SMP && defined CONFIG_HOTPLUG_CPU
+void arch_send_call_wakeup_ipi(int cpu);
+bool can_hotplug_cpu(void);
+#else
+static inline bool can_hotplug_cpu(void)
+{
+ return 0;
+}
+static inline void arch_send_call_wakeup_ipi(int cpu) { }
+#endif
+
#ifdef CONFIG_SMP
+enum ipi_message_type {
+ IPI_RESCHEDULE,
+ IPI_CALL_FUNC,
+ IPI_CALL_WAKEUP,
+ IPI_MAX
+};
+
+void send_ipi_message(const struct cpumask *to_whom,
+ enum ipi_message_type operation);
+
/* SMP initialization hook for setup_arch */
void __init setup_smp(void);
@@ -45,6 +66,13 @@ void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out);
*/
#define raw_smp_processor_id() (current_thread_info()->cpu)
+#ifdef CONFIG_HOTPLUG_CPU
+int __cpu_disable(void);
+void __cpu_die(unsigned int cpu);
+void cpu_play_dead(void);
+void boot_sec_cpu(void);
+#endif /* CONFIG_HOTPLUG_CPU */
+
#else
static inline int riscv_hartid_to_cpuid(int hartid)
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index e1274fc0..62043204 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_SMP) += smpboot.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_MODULE_SECTIONS) += module-sections.o
+obj-$(CONFIG_HOTPLUG_CPU) += cpu-hotplug.o
obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
obj-$(CONFIG_DYNAMIC_FTRACE) += mcount-dyn.o
diff --git a/arch/riscv/kernel/cpu-hotplug.c b/arch/riscv/kernel/cpu-hotplug.c
new file mode 100644
index 00000000..7a152972
--- /dev/null
+++ b/arch/riscv/kernel/cpu-hotplug.c
@@ -0,0 +1,72 @@
+// 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/sbi.h>
+
+bool can_hotplug_cpu(void)
+{
+ return true;
+}
+
+void arch_cpu_idle_dead(void)
+{
+ cpu_play_dead();
+}
+
+/*
+ * __cpu_disable runs on the processor to be shutdown.
+ */
+int __cpu_disable(void)
+{
+ int ret = 0;
+ unsigned int cpu = smp_processor_id();
+
+ 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 -
+ * waits until shutdown has completed, or it is timed out.
+ */
+void __cpu_die(unsigned int cpu)
+{
+ if (!cpu_wait_death(cpu, 5)) {
+ pr_err("CPU %u: didn't die\n", cpu);
+ return;
+ }
+ pr_notice("CPU%u: shutdown\n", cpu);
+ /*TODO: Do we need to verify is cpu is really dead */
+}
+
+/*
+ * Called from the idle thread for the CPU which has been shutdown.
+ *
+ */
+void cpu_play_dead(void)
+{
+ idle_task_exit();
+
+ (void)cpu_report_death();
+
+ /* Do not disable software interrupt to restart cpu after WFI */
+ csr_clear(sie, SIE_STIE | SIE_SEIE);
+ wait_for_software_interrupt();
+ boot_sec_cpu();
+}
+
+void arch_send_call_wakeup_ipi(int cpu)
+{
+ send_ipi_message(cpumask_of(cpu), IPI_CALL_WAKEUP);
+}
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 711190d4..07d9fb38 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -153,6 +153,19 @@ relocate:
j .Lsecondary_park
END(_start)
+#ifdef CONFIG_SMP
+.section .text
+.global boot_sec_cpu
+
+boot_sec_cpu:
+ /* clear all pending flags */
+ csrw sip, zero
+ /* Mask all interrupts */
+ csrw sie, zero
+ fence
+
+ tail smp_callin
+#endif
__PAGE_ALIGNED_BSS
/* Empty zero page */
.balign PAGE_SIZE
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 0cfac48a..7e14b0d9 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -53,6 +53,30 @@ asmlinkage void __irq_entry do_IRQ(struct pt_regs *regs,
unsigned long cause)
set_irq_regs(old_regs);
}
+/*
+ * This function doesn't return until a software interrupt is sent via IPI.
+ * Obviously, all the interrupts except software interrupt should be disabled
+ * before this function is called.
+ */
+void wait_for_software_interrupt(void)
+{
+ unsigned long sipval, sieval, scauseval;
+
+ /* clear all pending flags */
+ csr_write(sip, 0);
+ /* clear any previous scause data */
+ csr_write(scause, 0);
+
+ do {
+ wait_for_interrupt();
+ sipval = csr_read(sip);
+ sieval = csr_read(sie);
+ scauseval = csr_read(scause) & ~INTERRUPT_CAUSE_FLAG;
+ /* only break if wfi returns for an enabled interrupt */
+ } while ((sipval & sieval) == 0 &&
+ scauseval != INTERRUPT_CAUSE_SOFTWARE);
+}
+
void __init init_IRQ(void)
{
irqchip_init();
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index a5fac1b7..612f0c21 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -30,11 +30,11 @@
#include <linux/of_platform.h>
#include <linux/sched/task.h>
#include <linux/swiotlb.h>
+#include <linux/smp.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>
@@ -82,6 +82,7 @@ EXPORT_SYMBOL(empty_zero_page);
/* 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);
unsigned long __cpuid_to_hardid_map[NR_CPUS] = {
[0 ... NR_CPUS-1] = INVALID_HARTID
@@ -257,3 +258,17 @@ 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 = can_hotplug_cpu();
+ register_cpu(cpu, i);
+ }
+
+ return 0;
+}
+subsys_initcall(topology_init);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 89d95866..629456bb 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -32,12 +32,6 @@ static struct {
unsigned long bits ____cacheline_aligned;
} ipi_data[NR_CPUS] __cacheline_aligned;
-enum ipi_message_type {
- IPI_RESCHEDULE,
- IPI_CALL_FUNC,
- IPI_MAX
-};
-
int riscv_hartid_to_cpuid(int hartid)
{
int i = -1;
@@ -94,7 +88,7 @@ void riscv_software_interrupt(void)
}
}
-static void
+void
send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type
operation)
{
int cpuid, hartid;
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index f44ae780..a9138431 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -92,9 +92,12 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
task_stack_page(tidle) + THREAD_SIZE);
WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
+ arch_send_call_wakeup_ipi(cpu);
while (!cpu_online(cpu))
cpu_relax();
+ pr_notice("CPU%u: online\n", cpu);
+
return 0;
}
@@ -105,7 +108,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
/*
* C entry point for a secondary processor.
*/
-asmlinkage void __init smp_callin(void)
+asmlinkage void smp_callin(void)
{
struct mm_struct *mm = &init_mm;
@@ -115,7 +118,7 @@ asmlinkage void __init smp_callin(void)
trap_init();
notify_cpu_starting(smp_processor_id());
- set_cpu_online(smp_processor_id(), 1);
+ set_cpu_online(smp_processor_id(), true);
/*
* Remote TLB flushes are ignored while the CPU is offline, so emit
* a local TLB flush right now just in case.
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 24a9333d..8b331619 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -153,7 +153,7 @@ int is_valid_bugaddr(unsigned long pc)
}
#endif /* CONFIG_GENERIC_BUG */
-void __init trap_init(void)
+void trap_init(void)
{
/*
* Set sup0 scratch register to 0, indicating to exception vector
@@ -162,6 +162,6 @@ void __init trap_init(void)
csr_write(sscratch, 0);
/* Set the exception vector address */
csr_write(stvec, &handle_exception);
- /* Enable all interrupts */
- csr_write(sie, -1);
+ /* Enable all interrupts but timer interrupt*/
+ csr_set(sie, SIE_SSIE | SIE_SEIE);
}
--
2.7.4