x86/smpwakeup: Add a helper get the address of the wakeup mailbox

A Hyper-V VTL level 2 guest on a TDX environment needs to map the
physical page of the ACPI Multiprocessor Wakeup Structure as private
(encrypted). It needs to know the physical address of this structure.
Add a helper function.

Reviewed-by: Michael Kelley <[email protected]>
Suggested-by: Michael Kelley <[email protected]>
Signed-off-by: Ricardo Neri <[email protected]>

Author: ricardon

arch/x86/include/asm/smp.h

@@ -154,6 +154,7 @@ static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
 
 void acpi_setup_mp_wakeup_mailbox(u64 addr);
 struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
+u64 acpi_get_mp_wakeup_mailbox_paddr(void);
 
 #else /* !CONFIG_SMP */
 #define wbinvd_on_cpu(cpu)     wbinvd()

arch/x86/kernel/smpwakeup.c

@@ -81,3 +81,8 @@ struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
 {
 	return acpi_mp_wake_mailbox;
 }
+
+u64 acpi_get_mp_wakeup_mailbox_paddr(void)
+{
+	return acpi_mp_wake_mailbox_paddr;
+}