On Thu, Aug 16, 2018 at 5:26 AM, Atish Patra <atish.pa...@wdc.com> wrote: > Defining cpu_operations now helps adding cpu hotplug > support in proper manner. Moreover, it provides flexibility > in supporting other cpu enable/boot methods can be > supported in future. This patch has been largely inspired from > ARM64. However, a default boot method is defined for RISC-V unlike > ARM64. > > Signed-off-by: Atish Patra <atish.pa...@wdc.com> > --- > arch/riscv/include/asm/smp.h | 10 ++++++++++ > arch/riscv/kernel/smp.c | 8 ++++++++ > arch/riscv/kernel/smpboot.c | 34 ++++++++++++++++++++++++++++------ > 3 files changed, 46 insertions(+), 6 deletions(-) > > diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h > index 0763337b..2bb6e6c2 100644 > --- a/arch/riscv/include/asm/smp.h > +++ b/arch/riscv/include/asm/smp.h > @@ -28,6 +28,15 @@ > extern u64 __cpu_logical_map[NR_CPUS]; > #define cpu_logical_map(cpu) __cpu_logical_map[cpu] > > +struct cpu_operations { > + const char *name; > + int (*cpu_init)(unsigned int); > + int (*cpu_prepare)(unsigned int); > + int (*cpu_boot)(unsigned int, struct task_struct *); > +}; > +extern struct cpu_operations cpu_ops; > +void smp_set_cpu_ops(const struct cpu_operations *cpu_ops); > + > #ifdef CONFIG_SMP > > /* SMP initialization hook for setup_arch */ > @@ -57,5 +66,6 @@ static inline void cpuid_to_hartid_mask(const struct > cpumask *in, > cpumask_set_cpu(cpu_logical_map(0), out); > } > > + > #endif /* CONFIG_SMP */ > #endif /* _ASM_RISCV_SMP_H */ > diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c > index 4ab70480..5de58ced 100644 > --- a/arch/riscv/kernel/smp.c > +++ b/arch/riscv/kernel/smp.c > @@ -58,6 +58,14 @@ void cpuid_to_hartid_mask(const struct cpumask *in, struct > cpumask *out) > for_each_cpu(cpu, in) > cpumask_set_cpu(cpu_logical_map(cpu), out); > } > +struct cpu_operations cpu_ops __ro_after_init; > + > +void smp_set_cpu_ops(const struct cpu_operations *ops) > +{ > + if (ops) > + cpu_ops = *ops; > +} > +
Move both cpu_ops and smp_set_cpu_ops() to smpboot.c. This way you will not require to make cpu_ops as global. Further, I think cpu_ops should be a pointer and initial value should be &default_ops. Something like this: struct cpu_operations *cpu_ops __ro_after_init = &default_ops; > /* Unsupported */ > int setup_profiling_timer(unsigned int multiplier) > { > diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c > index 6ab2bb1b..045a1a45 100644 > --- a/arch/riscv/kernel/smpboot.c > +++ b/arch/riscv/kernel/smpboot.c > @@ -30,6 +30,7 @@ > #include <linux/irq.h> > #include <linux/of.h> > #include <linux/sched/task_stack.h> > +#include <linux/smp.h> > #include <asm/irq.h> > #include <asm/mmu_context.h> > #include <asm/tlbflush.h> > @@ -38,6 +39,7 @@ > > void *__cpu_up_stack_pointer[NR_CPUS]; > void *__cpu_up_task_pointer[NR_CPUS]; > +struct cpu_operations default_ops; > > void __init smp_prepare_boot_cpu(void) > { > @@ -53,6 +55,7 @@ void __init setup_smp(void) > int hart, found_boot_cpu = 0; > int cpuid = 1; > > + smp_set_cpu_ops(&default_ops); > while ((dn = of_find_node_by_type(dn, "cpu"))) { > hart = riscv_of_processor_hart(dn); > > @@ -73,10 +76,8 @@ void __init setup_smp(void) > BUG_ON(!found_boot_cpu); > } > > -int __cpu_up(unsigned int cpu, struct task_struct *tidle) > +int default_cpu_boot(unsigned int hartid, struct task_struct *tidle) > { > - int hartid = cpu_logical_map(cpu); > - tidle->thread_info.cpu = cpu; > /* > * On RISC-V systems, all harts boot on their own accord. Our _start > * selects the first hart to boot the kernel and causes the remainder > @@ -84,13 +85,28 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle) > * setup by that main hart. Writing __cpu_up_stack_pointer signals to > * the spinning harts that they can continue the boot process. > */ > - smp_mb(); > + > __cpu_up_stack_pointer[hartid] = task_stack_page(tidle) + THREAD_SIZE; > __cpu_up_task_pointer[hartid] = tidle; > + return 0; > +} > + > +int __cpu_up(unsigned int cpu, struct task_struct *tidle) > +{ > + int err = -1; > + int hartid = cpu_logical_map(cpu); > > - while (!cpu_online(cpu)) > - cpu_relax(); > + tidle->thread_info.cpu = cpu; > + smp_mb(); > > + if (cpu_ops.cpu_boot) > + err = cpu_ops.cpu_boot(hartid, tidle); > + if (!err) { > + while (!cpu_online(cpu)) > + cpu_relax(); > + } else { > + pr_err("CPU %d [hartid %d]failed to boot\n", cpu, hartid); > + } > return 0; > } > > @@ -117,3 +133,9 @@ asmlinkage void __init smp_callin(void) > preempt_disable(); > cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); > } > + > + > +struct cpu_operations default_ops = { > + .name = "default", > + .cpu_boot = default_cpu_boot, > +}; I think having dedicated source file for default_ops makes more sense so that we have a clear/simple reference implementation of cpu_operations. Eventually, we might have one source file for each type of SMP enable method. Try to keep smpboot.c generic and independent of any cpu_operations. What say? Regards, Anup