diff options
| author | Atish Patra <atishp@rivosinc.com> | 2022-01-20 01:09:15 -0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2022-01-20 09:27:08 -0800 |
| commit | c78f94f35cf6486c4057317e8de3ddc4c62e12c7 (patch) | |
| tree | da587266b5f6184ea6d71dad6b86588e5a904259 /arch/riscv/kernel/cpu_ops_spinwait.c | |
| parent | 410bb20a698d4c95c63e7f2b6f6f7d8da43795f5 (diff) | |
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 <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/kernel/cpu_ops_spinwait.c')
| -rw-r--r-- | arch/riscv/kernel/cpu_ops_spinwait.c | 27 |
1 files changed, 26 insertions, 1 deletions
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 <linux/errno.h> #include <linux/of.h> #include <linux/string.h> +#include <linux/sched/task_stack.h> #include <asm/cpu_ops.h> #include <asm/sbi.h> #include <asm/smp.h> 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); |