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

Rafael J. Wysocki
2025-05-05T09:55:18Z

On Sat, May 3, 2025 at 9:10 PM Ricardo Neri
<ricardo.neri-calderon@linux.intel.com> 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@linux.intel.com>
> ---
> 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;
> +}
> --