On Wed, 2024-01-24 at 14:55 +0200, Kirill A. Shutemov wrote:
> If the helper is defined, it is called instead of halt() to stop the CPU
> at the end of stop_this_cpu() and on crash CPU shutdown.
>
> ACPI MADT will use it to hand over the CPU to BIOS in order to be able
> to wake it up again after kexec.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Kai Huang <kai.huang@xxxxxxxxx>
> ---
> arch/x86/include/asm/smp.h | 1 +
> arch/x86/kernel/process.c | 7 +++++++
> arch/x86/kernel/reboot.c | 6 ++++++
> 3 files changed, 14 insertions(+)
>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 4fab2ed454f3..390d53fd34f9 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -38,6 +38,7 @@ struct smp_ops {
> int (*cpu_disable)(void);
> void (*cpu_die)(unsigned int cpu);
> void (*play_dead)(void);
> + void (*stop_this_cpu)(void);
>
> void (*send_call_func_ipi)(const struct cpumask *mask);
> void (*send_call_func_single_ipi)(int cpu);
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index ab49ade31b0d..00c1b957476d 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -835,6 +835,13 @@ void __noreturn stop_this_cpu(void *dummy)
> */
> cpumask_clear_cpu(cpu, &cpus_stop_mask);
>
> +#ifdef CONFIG_SMP
> + if (smp_ops.stop_this_cpu) {
> + smp_ops.stop_this_cpu();
> + unreachable();
> + }
> +#endif
> +
> for (;;) {
> /*
> * Use native_halt() so that memory contents don't change
> diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
> index 0574d4ad6b41..0a75efe579c0 100644
> --- a/arch/x86/kernel/reboot.c
> +++ b/arch/x86/kernel/reboot.c
> @@ -880,6 +880,12 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
> cpu_emergency_disable_virtualization();
>
> atomic_dec(&waiting_for_crash_ipi);
> +
> + if (smp_ops.stop_this_cpu) {
> + smp_ops.stop_this_cpu();
> + unreachable();
> + }
> +
> /* Assume hlt works */
> halt();
> for (;;)
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