From c78f94f35cf6486c4057317e8de3ddc4c62e12c7 Mon Sep 17 00:00:00 2001 From: Atish Patra Date: Thu, 20 Jan 2022 01:09:15 -0800 Subject: [PATCH] RISC-V: Use __cpu_up_stack/task_pointer only for spinwait method The __cpu_up_stack/task_pointer array is only used for spinwait method now. The per cpu array based lookup is also fragile for platforms with discontiguous/sparse hartids. The spinwait method is only used for M-mode Linux or older firmwares without SBI HSM extension. For general Linux systems, ordered booting method is preferred anyways to support cpu hotplug and kexec. Make sure that __cpu_up_stack/task_pointer is only used for spinwait method. Take this opportunity to rename it to __cpu_spinwait_stack/task_pointer to emphasize the purpose as well. Reviewed-by: Anup Patel Signed-off-by: Atish Patra Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/cpu_ops.h | 2 -- arch/riscv/kernel/cpu_ops.c | 16 ---------------- arch/riscv/kernel/cpu_ops_spinwait.c | 27 ++++++++++++++++++++++++++- arch/riscv/kernel/head.S | 4 ++-- arch/riscv/kernel/head.h | 4 ++-- 5 files changed, 30 insertions(+), 23 deletions(-) diff --git a/arch/riscv/include/asm/cpu_ops.h b/arch/riscv/include/asm/cpu_ops.h index a8ec3c5c1bd2..134590f1b843 100644 --- a/arch/riscv/include/asm/cpu_ops.h +++ b/arch/riscv/include/asm/cpu_ops.h @@ -40,7 +40,5 @@ struct cpu_operations { extern const struct cpu_operations *cpu_ops[NR_CPUS]; void __init cpu_set_ops(int cpu); -void cpu_update_secondary_bootdata(unsigned int cpuid, - struct task_struct *tidle); #endif /* ifndef __ASM_CPU_OPS_H */ diff --git a/arch/riscv/kernel/cpu_ops.c b/arch/riscv/kernel/cpu_ops.c index 3f5a38b03044..c1e30f403c3b 100644 --- a/arch/riscv/kernel/cpu_ops.c +++ b/arch/riscv/kernel/cpu_ops.c @@ -8,31 +8,15 @@ #include #include #include -#include #include #include #include const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init; -void *__cpu_up_stack_pointer[NR_CPUS] __section(".data"); -void *__cpu_up_task_pointer[NR_CPUS] __section(".data"); - extern const struct cpu_operations cpu_ops_sbi; extern const struct cpu_operations cpu_ops_spinwait; -void cpu_update_secondary_bootdata(unsigned int cpuid, - struct task_struct *tidle) -{ - int hartid = cpuid_to_hartid_map(cpuid); - - /* Make sure tidle is updated */ - smp_mb(); - WRITE_ONCE(__cpu_up_stack_pointer[hartid], - task_stack_page(tidle) + THREAD_SIZE); - WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle); -} - void __init cpu_set_ops(int cpuid) { #if IS_ENABLED(CONFIG_RISCV_SBI) diff --git a/arch/riscv/kernel/cpu_ops_spinwait.c b/arch/riscv/kernel/cpu_ops_spinwait.c index b2c957bb68c1..346847f6c41c 100644 --- a/arch/riscv/kernel/cpu_ops_spinwait.c +++ b/arch/riscv/kernel/cpu_ops_spinwait.c @@ -6,11 +6,36 @@ #include #include #include +#include #include #include #include const struct cpu_operations cpu_ops_spinwait; +void *__cpu_spinwait_stack_pointer[NR_CPUS] __section(".data"); +void *__cpu_spinwait_task_pointer[NR_CPUS] __section(".data"); + +static void cpu_update_secondary_bootdata(unsigned int cpuid, + struct task_struct *tidle) +{ + int hartid = cpuid_to_hartid_map(cpuid); + + /* + * The hartid must be less than NR_CPUS to avoid out-of-bound access + * errors for __cpu_spinwait_stack/task_pointer. That is not always possible + * for platforms with discontiguous hartid numbering scheme. That's why + * spinwait booting is not the recommended approach for any platforms + * booting Linux in S-mode and can be disabled in the future. + */ + if (hartid == INVALID_HARTID || hartid >= NR_CPUS) + return; + + /* Make sure tidle is updated */ + smp_mb(); + WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid], + task_stack_page(tidle) + THREAD_SIZE); + WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle); +} static int spinwait_cpu_prepare(unsigned int cpuid) { @@ -28,7 +53,7 @@ static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle) * selects the first cpu to boot the kernel and causes the remainder * of the cpus to spin in a loop waiting for their stack pointer to be * setup by that main cpu. Writing to bootdata - * (i.e __cpu_up_stack_pointer) signals to the spinning cpus that they + * (i.e __cpu_spinwait_stack_pointer) signals to the spinning cpus that they * can continue the boot process. */ cpu_update_secondary_bootdata(cpuid, tidle); diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index 05ea372e1909..efa9cd499ac6 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -347,9 +347,9 @@ clear_bss_done: csrw CSR_TVEC, a3 slli a3, a0, LGREG - la a1, __cpu_up_stack_pointer + la a1, __cpu_spinwait_stack_pointer XIP_FIXUP_OFFSET a1 - la a2, __cpu_up_task_pointer + la a2, __cpu_spinwait_task_pointer XIP_FIXUP_OFFSET a2 add a1, a3, a1 add a2, a3, a2 diff --git a/arch/riscv/kernel/head.h b/arch/riscv/kernel/head.h index aabbc3ac3e48..5393cca77790 100644 --- a/arch/riscv/kernel/head.h +++ b/arch/riscv/kernel/head.h @@ -16,7 +16,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa); asmlinkage void __init __copy_data(void); #endif -extern void *__cpu_up_stack_pointer[]; -extern void *__cpu_up_task_pointer[]; +extern void *__cpu_spinwait_stack_pointer[]; +extern void *__cpu_spinwait_task_pointer[]; #endif /* __ASM_HEAD_H */ -- 2.25.1