a638b0461b
Top of the kernel thread stack should be reserved for pt_regs. However this is not the case for the idle threads of the secondary boot harts. Their stacks overlap with their pt_regs, so both may get corrupted. Similar issue has been fixed for the primary hart, seec7cdd96eca("riscv: prevent stack corruption by reserving task_pt_regs(p) early"). However that fix was not propagated to the secondary harts. The problem has been noticed in some CPU hotplug tests with V enabled. The function smp_callin stored several registers on stack, corrupting top of pt_regs structure including status field. As a result, kernel attempted to save or restore inexistent V context. Fixes:9a2451f186("RISC-V: Avoid using per cpu array for ordered booting") Fixes:2875fe0561("RISC-V: Add cpu_ops and modify default booting method") Signed-off-by: Sergey Matyukevich <sergey.matyukevich@syntacore.com> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com> Link: https://lore.kernel.org/r/20240523084327.2013211-1-geomatsi@gmail.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
58 lines
1.8 KiB
C
58 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2020 Western Digital Corporation or its affiliates.
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*/
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#include <linux/errno.h>
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#include <linux/of.h>
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#include <linux/string.h>
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#include <linux/sched/task_stack.h>
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#include <asm/cpu_ops.h>
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#include <asm/sbi.h>
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#include <asm/smp.h>
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#include "head.h"
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const struct cpu_operations cpu_ops_spinwait;
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void *__cpu_spinwait_stack_pointer[NR_CPUS] __section(".data");
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void *__cpu_spinwait_task_pointer[NR_CPUS] __section(".data");
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static void cpu_update_secondary_bootdata(unsigned int cpuid,
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struct task_struct *tidle)
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{
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unsigned long hartid = cpuid_to_hartid_map(cpuid);
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/*
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* The hartid must be less than NR_CPUS to avoid out-of-bound access
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* errors for __cpu_spinwait_stack/task_pointer. That is not always possible
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* for platforms with discontiguous hartid numbering scheme. That's why
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* spinwait booting is not the recommended approach for any platforms
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* booting Linux in S-mode and can be disabled in the future.
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*/
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if (hartid == INVALID_HARTID || hartid >= (unsigned long) NR_CPUS)
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return;
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/* Make sure tidle is updated */
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smp_mb();
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WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid], task_pt_regs(tidle));
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WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);
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}
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static int spinwait_cpu_start(unsigned int cpuid, struct task_struct *tidle)
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{
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/*
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* In this protocol, all cpus boot on their own accord. _start
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* selects the first cpu to boot the kernel and causes the remainder
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* of the cpus to spin in a loop waiting for their stack pointer to be
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* setup by that main cpu. Writing to bootdata
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* (i.e __cpu_spinwait_stack_pointer) signals to the spinning cpus that they
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* can continue the boot process.
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*/
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cpu_update_secondary_bootdata(cpuid, tidle);
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return 0;
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}
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const struct cpu_operations cpu_ops_spinwait = {
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.cpu_start = spinwait_cpu_start,
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};
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