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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>
This commit is contained in:
Atish Patra 2022-01-20 01:09:15 -08:00 committed by Palmer Dabbelt
parent 410bb20a69
commit c78f94f35c
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
5 changed files with 30 additions and 23 deletions
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2
arch/riscv/include/asm/cpu_ops.h
View File

@ -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 */

16
arch/riscv/kernel/cpu_ops.c
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@ -8,31 +8,15 @@
#include <linux/of.h>
#include <linux/string.h>
#include <linux/sched.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[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)

27
arch/riscv/kernel/cpu_ops_spinwait.c
View File

@ -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);

4
arch/riscv/kernel/head.S
View File

@ -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

4
arch/riscv/kernel/head.h
View File

@ -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 */