[PATCH v3 01/13] x86/acpi: Add a helper function to setup the wakeup mailbox

Ricardo Neri
2025-05-03T19:10:11Z

In preparation to move the functionality to wake secondary CPUs up out of
the ACPI code, add a helper function that stores the physical address of
the mailbox and updates the wakeup_secondary_cpu_64() APIC callback.

There is a slight change in behavior: now the APIC callback is updated
before configuring CPU hotplug offline behavior. This is fine as the APIC
callback continues to be updated unconditionally, regardless of the
restriction on CPU offlining.

The wakeup mailbox is only supported for CONFIG_X86_64 and needed only with
CONFIG_SMP=y.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
Changes since v2:
- Introduced this patch.

Changes since v1:
- N/A
---
arch/x86/include/asm/smp.h | 4 ++++
arch/x86/kernel/acpi/madt_wakeup.c | 10 +++++++---
2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 0c1c68039d6f..3622951d2ee0 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -146,6 +146,10 @@ static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
return per_cpu(cpu_l2c_shared_map, cpu);
}

+#ifdef CONFIG_X86_64
+void setup_mp_wakeup_mailbox(u64 addr);
+#endif
+
#else /* !CONFIG_SMP */
#define wbinvd_on_cpu(cpu) wbinvd()
static inline int wbinvd_on_all_cpus(void)
diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index f36f28405dcc..04de3db307de 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -227,7 +227,7 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,

acpi_table_print_madt_entry(&header->common);

- acpi_mp_wake_mailbox_paddr = mp_wake->mailbox_address;
+ setup_mp_wakeup_mailbox(mp_wake->mailbox_address);

if (mp_wake->version >= ACPI_MADT_MP_WAKEUP_VERSION_V1 &&
mp_wake->header.length >= ACPI_MADT_MP_WAKEUP_SIZE_V1) {
@@ -243,7 +243,11 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
acpi_mp_disable_offlining(mp_wake);
}

- apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
-
return 0;
}
+
+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);
+}
--
2.43.0