linux_dsm_epyc7002/arch/riscv/kernel/cpu_ops.c
Zong Li d6d5161280
riscv: force __cpu_up_ variables to put in data section
Put __cpu_up_stack_pointer and __cpu_up_task_pointer in data section.
Currently, these two variables are put in bss section, there is a
potential risk that secondary harts get the uninitialized value before
main hart finishing the bss clearing. In this case, all secondary
harts would pass the waiting loop and enable the MMU before main hart
set up the page table.

This issue happens on random booting of multiple harts, which means
it will manifest for BBL and OpenSBI v0.6 (or older version). In OpenSBI
v0.7 (or higher version), we have HSM extension so all the secondary harts
are brought-up by Linux kernel in an orderly fashion. This means we don't
need this change for OpenSBI v0.7 (or higher version).

Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
2020-05-04 15:03:25 -07:00

47 lines
1.2 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2020 Western Digital Corporation or its affiliates.
*/
#include <linux/errno.h>
#include <linux/mm.h>
#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)
if (sbi_probe_extension(SBI_EXT_HSM) > 0) {
if (!cpuid)
pr_info("SBI v0.2 HSM extension detected\n");
cpu_ops[cpuid] = &cpu_ops_sbi;
} else
#endif
cpu_ops[cpuid] = &cpu_ops_spinwait;
}