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

[Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>]

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.

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();
 	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;
+}
-- 
2.43.0