Re: [PATCH v3 02/13] x86/acpi: Add a helper function to get a pointer to the wakeup mailbox

[Rafael J. Wysocki]

On Sat, May 3, 2025 at 9:10 PM Ricardo Neri
<ricardo.neri-calderon@xxxxxxxxxxxxxxx> wrote:
>
> In preparation to move the functionality to wake secondary CPUs up out
> of the ACPI code, add a helper function to get a pointer to the mailbox.
>
> Use this helper function only in the portions of the code for which the
> variable acpi_mp_wake_mailbox will be out of scope once it is relocated
> out of the ACPI directory.
>
> The wakeup mailbox is only supported for CONFIG_X86_64 and needed only
> with CONFIG_SMP.
>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
> ---
> Changes since v2:
>  - Introduced this patch.

Have you considered merging it with the previous patch?  They both do
analogous things.

> Changes since v1:
>  - N/A
> ---
>  arch/x86/include/asm/smp.h         |  1 +
>  arch/x86/kernel/acpi/madt_wakeup.c | 12 +++++++++---
>  2 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 3622951d2ee0..97bfbd0d24d4 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -148,6 +148,7 @@ static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
>
>  #ifdef CONFIG_X86_64
>  void setup_mp_wakeup_mailbox(u64 addr);
> +struct acpi_madt_multiproc_wakeup_mailbox *get_mp_wakeup_mailbox(void);
>  #endif
>
>  #else /* !CONFIG_SMP */
> diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
> index 04de3db307de..6b9e41a24574 100644
> --- a/arch/x86/kernel/acpi/madt_wakeup.c
> +++ b/arch/x86/kernel/acpi/madt_wakeup.c
> @@ -37,6 +37,7 @@ static void acpi_mp_play_dead(void)
>
>  static void acpi_mp_cpu_die(unsigned int cpu)
>  {
> +       struct acpi_madt_multiproc_wakeup_mailbox *mailbox = get_mp_wakeup_mailbox();

I'd prefer acpi_get_mp_wakeup_mailbox().

>         u32 apicid = per_cpu(x86_cpu_to_apicid, cpu);
>         unsigned long timeout;
>
> @@ -46,13 +47,13 @@ static void acpi_mp_cpu_die(unsigned int cpu)
>          *
>          * BIOS has to clear 'command' field of the mailbox.
>          */
> -       acpi_mp_wake_mailbox->apic_id = apicid;
> -       smp_store_release(&acpi_mp_wake_mailbox->command,
> +       mailbox->apic_id = apicid;
> +       smp_store_release(&mailbox->command,
>                           ACPI_MP_WAKE_COMMAND_TEST);
>
>         /* Don't wait longer than a second. */
>         timeout = USEC_PER_SEC;
> -       while (READ_ONCE(acpi_mp_wake_mailbox->command) && --timeout)
> +       while (READ_ONCE(mailbox->command) && --timeout)
>                 udelay(1);
>
>         if (!timeout)
> @@ -251,3 +252,8 @@ void __init setup_mp_wakeup_mailbox(u64 mailbox_paddr)
>         acpi_mp_wake_mailbox_paddr = mailbox_paddr;
>         apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
>  }
> +
> +struct acpi_madt_multiproc_wakeup_mailbox *get_mp_wakeup_mailbox(void)
> +{
> +       return acpi_mp_wake_mailbox;
> +}
> --