# \[PATCH v6 08/10\] x86/smpwakeup: Add a helper get the address of the wakeup mailbox

- From: Ricardo Neri \<hidden\>
- Date: 2025-10-17 02:48:54 
- List: linux-devicetree
- Page: https://ratatoskr.run/linux-devicetree/2025/10/3255083
- Thread: https://ratatoskr.run/linux-hyperv/2025/10/3255076/t.md

```text
A Hyper-V VTL level 2 guest in 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
to retrieve the address.

Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <redacted>
Suggested-by: Michael Kelley <redacted>
Signed-off-by: Ricardo Neri <redacted>
---
Changes since v5:
 - Added Reviewed-by tag from Dexuan. Thanks!

Changes since v4:
 - None

Changes since v3:
 - Renamed function to acpi_get_mp_wakeup_mailbox_paddr().
 - Added Reviewed-by tag from Michael. Thanks!

Changes since v2:
 - Introduced this patch

Changes since v1:
 - N/A
---
 arch/x86/include/asm/smp.h  | 1 +
 arch/x86/kernel/smpwakeup.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 47ac4381a805..71de1963f984 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -151,6 +151,7 @@ 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()
diff --git a/arch/x86/kernel/smpwakeup.c b/arch/x86/kernel/smpwakeup.c
index 5089bcda615d..f730a66b6fc8 100644
--- a/arch/x86/kernel/smpwakeup.c
+++ b/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;
+}

-- 
2.43.0

```