[PATCH v6 2/3] x86: Implement acpi_get_cpu_uid()

Chengwen Feng
2026-03-12T07:23:59Z

Add acpi_get_cpu_uid() implementation for x86, replacing the existing
cpu_acpi_id() function. This completes the unified ACPI Processor UID
retrieval interface across all ACPI-enabled architectures.

Cc: stable@vger.kernel.org
Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
---
arch/x86/include/asm/cpu.h | 1 -
arch/x86/include/asm/smp.h | 1 -
arch/x86/kernel/cpu/common.c | 15 +++++++++++++++
arch/x86/xen/enlighten_hvm.c | 5 +++--
include/linux/acpi.h | 2 --
5 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index ad235dda1ded..57a0786dfd75 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -11,7 +11,6 @@

#ifndef CONFIG_SMP
#define cpu_physical_id(cpu) boot_cpu_physical_apicid
-#define cpu_acpi_id(cpu) 0
#endif /* CONFIG_SMP */

#ifdef CONFIG_HOTPLUG_CPU
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 84951572ab81..05d1d479b4cf 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -130,7 +130,6 @@ __visible void smp_call_function_interrupt(struct pt_regs *regs);
__visible void smp_call_function_single_interrupt(struct pt_regs *r);

#define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu)
-#define cpu_acpi_id(cpu) per_cpu(x86_cpu_to_acpiid, cpu)

/*
* This function is needed by all SMP systems. It must _always_ be valid
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 1c3261cae40c..3081557542c7 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -28,6 +28,7 @@
#include <linux/stackprotector.h>
#include <linux/utsname.h>
#include <linux/efi.h>
+#include <linux/acpi.h>

#include <asm/alternative.h>
#include <asm/cmdline.h>
@@ -57,6 +58,7 @@
#include <asm/asm.h>
#include <asm/bugs.h>
#include <asm/cpu.h>
+#include <asm/smp.h>
#include <asm/mce.h>
#include <asm/msr.h>
#include <asm/cacheinfo.h>
@@ -2643,3 +2645,16 @@ void __init arch_cpu_finalize_init(void)
*/
mem_encrypt_init();
}
+
+int acpi_get_cpu_uid(unsigned int cpu, u32 *uid)
+{
+ if (cpu >= nr_cpu_ids)
+ return -EINVAL;
+#ifndef CONFIG_SMP
+ *uid = 0;
+#else
+ *uid = per_cpu(x86_cpu_to_acpiid, cpu);
+#endif
+ return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_get_cpu_uid);
diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index fe57ff85d004..2f9fa27e5a3c 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -151,6 +151,7 @@ static void xen_hvm_crash_shutdown(struct pt_regs *regs)

static int xen_cpu_up_prepare_hvm(unsigned int cpu)
{
+ u32 cpu_uid;
int rc = 0;

/*
@@ -161,8 +162,8 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu)
*/
xen_uninit_lock_cpu(cpu);

- if (cpu_acpi_id(cpu) != CPU_ACPIID_INVALID)
- per_cpu(xen_vcpu_id, cpu) = cpu_acpi_id(cpu);
+ if (acpi_get_cpu_uid(cpu, &cpu_uid) == 0)
+ per_cpu(xen_vcpu_id, cpu) = cpu_uid;
else
per_cpu(xen_vcpu_id, cpu) = cpu;
xen_vcpu_setup(cpu);
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 035094a55f18..90a1fdcb7eb9 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -324,7 +324,6 @@ int acpi_unmap_cpu(int cpu);

acpi_handle acpi_get_processor_handle(int cpu);

-#ifndef CONFIG_X86
/*
* acpi_get_cpu_uid() - Get ACPI Processor UID of a specified CPU from MADT table
* @cpu: Logical CPU number (0-based)
@@ -335,7 +334,6 @@ acpi_handle acpi_get_processor_handle(int cpu);
* -ENODEV if the ACPI Processor UID for the specified CPU is not found.
*/
int acpi_get_cpu_uid(unsigned int cpu, u32 *uid);
-#endif

#ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
int acpi_get_ioapic_id(acpi_handle handle, u32 gsi_base, u64 *phys_addr);
--
2.17.1