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

Peter Zijlstra
2026-03-12T11:02:25Z

On Thu, Mar 12, 2026 at 03:23:15PM +0800, Chengwen Feng wrote:
> 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);

This doesn't look right, it will now set CPU_ACPIID_INVALID, while
previously it would not.