[PATCH v6 0/3] Fix get cpu steer-tag fail on ARM64 platform

[PATCH v6 0/3] Fix get cpu steer-tag fail on ARM64 platform

[Chengwen Feng]

This patchset fixes the failure of CPU steer tag retrieval on ARM64
platforms. The series is structured as follows:

1. First commit: Mechanical rename of the ACPI Processor UID retrieval
   interface (no functional changes) to align naming conventions across
   architectures;
2. Second commit: Implement acpi_get_cpu_uid() for the x86 platform to
   complete the unified ACPI Processor UID interface across all
   ACPI-enabled architectures;
3. Third commit: Implement the core fix for the CPU steer tag retrieval
   logic on ARM64 (the root cause of the retrieval failure).

The renaming and x86 implementation lay the groundwork for the unified
ACPI interface required by the ARM64 steer tag fix, ensuring consistent
CPU UID retrieval across architectures before addressing the functional
bug.

---
Changes in v6:
- Rename existing get_acpi_id_for_cpu() to acpi_get_cpu_uid()
- Split x86's modify as one commit

Changes in v5:
- Refine commit-log of commit 2/2
- Replace cpu_acpi_id() by acpi_get_cpu_acpi_id() on x86

Changes in v4:
- Split the rename into a separate commit.

Changes in v3:
- Rename existing get_acpi_id_for_cpu() to acpi_get_cpu_acpi_id() other
  than add one new API.

Changes in v2:
- Add ECN _DSM reference doc name and its URL.
- Separate implement acpi_get_cpu_acpi_id() in each arch which supports
  ACPI.
- Refine commit-log.

Chengwen Feng (2):
  ACPI: Rename get_acpi_id_for_cpu() to acpi_get_cpu_acpi_id() on
    non-x86
  PCI/TPH: Fix get cpu steer-tag fail on ARM64 platform

Chengwen Feng (3):
  ACPI: Rename get_acpi_id_for_cpu() to acpi_get_cpu_uid() on non-x86
  x86: Implement acpi_get_cpu_uid()
  PCI/TPH: Fix get cpu steer-tag fail on ARM64 platform

 Documentation/PCI/tph.rst          |  4 +--
 arch/arm64/include/asm/acpi.h      | 16 +---------
 arch/arm64/kernel/acpi.c           | 16 ++++++++++
 arch/arm64/kernel/acpi_numa.c      | 15 ++++++++++
 arch/loongarch/include/asm/acpi.h  |  5 ----
 arch/loongarch/kernel/acpi.c       |  9 ++++++
 arch/riscv/include/asm/acpi.h      |  4 ---
 arch/riscv/kernel/acpi.c           | 16 ++++++++++
 arch/riscv/kernel/acpi_numa.c      |  8 +++--
 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 ++--
 drivers/acpi/pptt.c                | 47 +++++++++++++++++++++---------
 drivers/acpi/riscv/rhct.c          |  7 ++++-
 drivers/pci/tph.c                  | 16 ++++++----
 drivers/perf/arm_cspmu/arm_cspmu.c |  6 ++--
 include/linux/acpi.h               | 11 +++++++
 include/linux/pci-tph.h            |  4 +--
 19 files changed, 151 insertions(+), 55 deletions(-)

-- 
2.17.1

[PATCH v6 1/3] ACPI: Rename get_acpi_id_for_cpu() to acpi_get_cpu_uid() on non-x86

[Chengwen Feng]

To unify the CPU ACPI ID retrieval interface across architectures,
rename the existing get_acpi_id_for_cpu() function to
acpi_get_cpu_uid() on arm64/riscv/loongarch platforms.

This is a pure rename with no functional change, preparing for a
consistent ACPI Processor UID retrieval interface across all ACPI-enabled
platforms.

Note: Move the ARM64-specific get_cpu_for_acpi_id() implementation to
      arch/arm64/kernel/acpi_numa.c to fix compilation errors from
      circular header dependencies introduced by the rename.

Cc: stable@vger.kernel.org
Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
---
 arch/arm64/include/asm/acpi.h      | 16 +---------
 arch/arm64/kernel/acpi.c           | 16 ++++++++++
 arch/arm64/kernel/acpi_numa.c      | 15 ++++++++++
 arch/loongarch/include/asm/acpi.h  |  5 ----
 arch/loongarch/kernel/acpi.c       |  9 ++++++
 arch/riscv/include/asm/acpi.h      |  4 ---
 arch/riscv/kernel/acpi.c           | 16 ++++++++++
 arch/riscv/kernel/acpi_numa.c      |  8 +++--
 drivers/acpi/pptt.c                | 47 +++++++++++++++++++++---------
 drivers/acpi/riscv/rhct.c          |  7 ++++-
 drivers/perf/arm_cspmu/arm_cspmu.c |  6 ++--
 include/linux/acpi.h               | 13 +++++++++
 12 files changed, 120 insertions(+), 42 deletions(-)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index c07a58b96329..106a08556cbf 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -114,22 +114,8 @@ static inline bool acpi_has_cpu_in_madt(void)
 }
 
 struct acpi_madt_generic_interrupt *acpi_cpu_get_madt_gicc(int cpu);
-static inline u32 get_acpi_id_for_cpu(unsigned int cpu)
-{
-	return	acpi_cpu_get_madt_gicc(cpu)->uid;
-}
-
-static inline int get_cpu_for_acpi_id(u32 uid)
-{
-	int cpu;
-
-	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
-		if (acpi_cpu_get_madt_gicc(cpu) &&
-		    uid == get_acpi_id_for_cpu(cpu))
-			return cpu;
 
-	return -EINVAL;
-}
+int get_cpu_for_acpi_id(u32 uid);
 
 static inline void arch_fix_phys_package_id(int num, u32 slot) { }
 void __init acpi_init_cpus(void);
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index af90128cfed5..984a11788265 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -458,3 +458,19 @@ int acpi_unmap_cpu(int cpu)
 }
 EXPORT_SYMBOL(acpi_unmap_cpu);
 #endif /* CONFIG_ACPI_HOTPLUG_CPU */
+
+int acpi_get_cpu_uid(unsigned int cpu, u32 *uid)
+{
+	struct acpi_madt_generic_interrupt *gicc;
+
+	if (cpu >= nr_cpu_ids)
+		return -EINVAL;
+
+	gicc = acpi_cpu_get_madt_gicc(cpu);
+	if (gicc == NULL)
+		return -ENODEV;
+
+	*uid = gicc->uid;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_get_cpu_uid);
diff --git a/arch/arm64/kernel/acpi_numa.c b/arch/arm64/kernel/acpi_numa.c
index 2465f291c7e1..56e2e486e49b 100644
--- a/arch/arm64/kernel/acpi_numa.c
+++ b/arch/arm64/kernel/acpi_numa.c
@@ -34,6 +34,21 @@ int __init acpi_numa_get_nid(unsigned int cpu)
 	return acpi_early_node_map[cpu];
 }
 
+int get_cpu_for_acpi_id(u32 uid)
+{
+	u32 cpu_uid;
+	int cpu;
+	int ret;
+
+	for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
+		ret = acpi_get_cpu_uid(cpu, &cpu_uid);
+		if (ret == 0 && uid == cpu_uid)
+			return cpu;
+	}
+
+	return -EINVAL;
+}
+
 static int __init acpi_parse_gicc_pxm(union acpi_subtable_headers *header,
 				      const unsigned long end)
 {
diff --git a/arch/loongarch/include/asm/acpi.h b/arch/loongarch/include/asm/acpi.h
index 7376840fa9f7..eda9d4d0a493 100644
--- a/arch/loongarch/include/asm/acpi.h
+++ b/arch/loongarch/include/asm/acpi.h
@@ -40,11 +40,6 @@ extern struct acpi_madt_core_pic acpi_core_pic[MAX_CORE_PIC];
 
 extern int __init parse_acpi_topology(void);
 
-static inline u32 get_acpi_id_for_cpu(unsigned int cpu)
-{
-	return acpi_core_pic[cpu_logical_map(cpu)].processor_id;
-}
-
 #endif /* !CONFIG_ACPI */
 
 #define ACPI_TABLE_UPGRADE_MAX_PHYS ARCH_LOW_ADDRESS_LIMIT
diff --git a/arch/loongarch/kernel/acpi.c b/arch/loongarch/kernel/acpi.c
index 1367ca759468..058f0dbe8e8f 100644
--- a/arch/loongarch/kernel/acpi.c
+++ b/arch/loongarch/kernel/acpi.c
@@ -385,3 +385,12 @@ int acpi_unmap_cpu(int cpu)
 EXPORT_SYMBOL(acpi_unmap_cpu);
 
 #endif /* CONFIG_ACPI_HOTPLUG_CPU */
+
+int acpi_get_cpu_uid(unsigned int cpu, u32 *uid)
+{
+	if (cpu >= nr_cpu_ids)
+		return -EINVAL;
+	*uid = acpi_core_pic[cpu_logical_map(cpu)].processor_id;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_get_cpu_uid);
diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
index 6e13695120bc..26ab37c171bc 100644
--- a/arch/riscv/include/asm/acpi.h
+++ b/arch/riscv/include/asm/acpi.h
@@ -61,10 +61,6 @@ static inline void arch_fix_phys_package_id(int num, u32 slot) { }
 
 void acpi_init_rintc_map(void);
 struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
-static inline u32 get_acpi_id_for_cpu(int cpu)
-{
-	return acpi_cpu_get_madt_rintc(cpu)->uid;
-}
 
 int acpi_get_riscv_isa(struct acpi_table_header *table,
 		       unsigned int cpu, const char **isa);
diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
index 71698ee11621..bde810d02c4f 100644
--- a/arch/riscv/kernel/acpi.c
+++ b/arch/riscv/kernel/acpi.c
@@ -337,3 +337,19 @@ int raw_pci_write(unsigned int domain, unsigned int bus,
 }
 
 #endif	/* CONFIG_PCI */
+
+int acpi_get_cpu_uid(unsigned int cpu, u32 *uid)
+{
+	struct acpi_madt_rintc *rintc;
+
+	if (cpu >= nr_cpu_ids)
+		return -EINVAL;
+
+	rintc = acpi_cpu_get_madt_rintc(cpu);
+	if (rintc == NULL)
+		return -ENODEV;
+
+	*uid = rintc->uid;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_get_cpu_uid);
diff --git a/arch/riscv/kernel/acpi_numa.c b/arch/riscv/kernel/acpi_numa.c
index 130769e3a99c..cd8adc9857e3 100644
--- a/arch/riscv/kernel/acpi_numa.c
+++ b/arch/riscv/kernel/acpi_numa.c
@@ -37,11 +37,15 @@ static int __init acpi_numa_get_nid(unsigned int cpu)
 
 static inline int get_cpu_for_acpi_id(u32 uid)
 {
+	u32 cpu_uid;
 	int cpu;
+	int ret;
 
-	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
-		if (uid == get_acpi_id_for_cpu(cpu))
+	for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
+		ret = acpi_get_cpu_uid(cpu, &cpu_uid);
+		if (ret == 0 && uid == cpu_uid)
 			return cpu;
+	}
 
 	return -EINVAL;
 }
diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index de5f8c018333..d034a217e85b 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -459,11 +459,14 @@ static void cache_setup_acpi_cpu(struct acpi_table_header *table,
 {
 	struct acpi_pptt_cache *found_cache;
 	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
-	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	u32 acpi_cpu_id;
 	struct cacheinfo *this_leaf;
 	unsigned int index = 0;
 	struct acpi_pptt_processor *cpu_node = NULL;
 
+	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
+		return;
+
 	while (index < get_cpu_cacheinfo(cpu)->num_leaves) {
 		this_leaf = this_cpu_ci->info_list + index;
 		found_cache = acpi_find_cache_node(table, acpi_cpu_id,
@@ -546,7 +549,10 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table,
 				     unsigned int cpu, int level, int flag)
 {
 	struct acpi_pptt_processor *cpu_node;
-	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	u32 acpi_cpu_id;
+
+	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
+		return -ENOENT;
 
 	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
 	if (cpu_node) {
@@ -614,18 +620,22 @@ static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
  *
  * Check the node representing a CPU for a given flag.
  *
- * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be found or
- *	   the table revision isn't new enough.
+ * Return: -ENOENT if can't get CPU's ACPI Processor UID, the PPTT doesn't
+ *	   exist, the CPU cannot be found or the table revision isn't new
+ *	   enough.
  *	   1, any passed flag set
  *	   0, flag unset
  */
 static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
 {
 	struct acpi_table_header *table;
-	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	u32 acpi_cpu_id;
 	struct acpi_pptt_processor *cpu_node = NULL;
 	int ret = -ENOENT;
 
+	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
+		return -ENOENT;
+
 	table = acpi_get_pptt();
 	if (!table)
 		return -ENOENT;
@@ -651,7 +661,8 @@ static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
  * in the PPTT. Errors caused by lack of a PPTT table, or otherwise, return 0
  * indicating we didn't find any cache levels.
  *
- * Return: -ENOENT if no PPTT table or no PPTT processor struct found.
+ * Return: -ENOENT if no PPTT table, can't get CPU's ACPI Process UID or no PPTT
+ *	   processor struct found.
  *	   0 on success.
  */
 int acpi_get_cache_info(unsigned int cpu, unsigned int *levels,
@@ -671,7 +682,8 @@ int acpi_get_cache_info(unsigned int cpu, unsigned int *levels,
 
 	pr_debug("Cache Setup: find cache levels for CPU=%d\n", cpu);
 
-	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id))
+		return -ENOENT;
 	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
 	if (!cpu_node)
 		return -ENOENT;
@@ -780,8 +792,9 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
  * It may not exist in single CPU systems. In simple multi-CPU systems,
  * it may be equal to the package topology level.
  *
- * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be found
- * or there is no toplogy level above the CPU..
+ * Return: -ENOENT if the PPTT doesn't exist, can't get CPU's ACPI
+ * Processor UID, the CPU cannot be found or there is no toplogy level
+ * above the CPU.
  * Otherwise returns a value which represents the package for this CPU.
  */
 
@@ -797,7 +810,8 @@ int find_acpi_cpu_topology_cluster(unsigned int cpu)
 	if (!table)
 		return -ENOENT;
 
-	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
+		return -ENOENT;
 	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
 	if (!cpu_node || !cpu_node->parent)
 		return -ENOENT;
@@ -872,7 +886,8 @@ static void acpi_pptt_get_child_cpus(struct acpi_table_header *table_hdr,
 	cpumask_clear(cpus);
 
 	for_each_possible_cpu(cpu) {
-		acpi_id = get_acpi_id_for_cpu(cpu);
+		if (acpi_get_cpu_uid(cpu, &acpi_id) != 0)
+			continue;
 		cpu_node = acpi_find_processor_node(table_hdr, acpi_id);
 
 		while (cpu_node) {
@@ -966,10 +981,13 @@ int find_acpi_cache_level_from_id(u32 cache_id)
 	for_each_possible_cpu(cpu) {
 		bool empty;
 		int level = 1;
-		u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+		u32 acpi_cpu_id;
 		struct acpi_pptt_cache *cache;
 		struct acpi_pptt_processor *cpu_node;
 
+		if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
+			continue;
+
 		cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
 		if (!cpu_node)
 			continue;
@@ -1030,10 +1048,13 @@ int acpi_pptt_get_cpumask_from_cache_id(u32 cache_id, cpumask_t *cpus)
 	for_each_possible_cpu(cpu) {
 		bool empty;
 		int level = 1;
-		u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+		u32 acpi_cpu_id;
 		struct acpi_pptt_cache *cache;
 		struct acpi_pptt_processor *cpu_node;
 
+		if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
+			continue;
+
 		cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
 		if (!cpu_node)
 			continue;
diff --git a/drivers/acpi/riscv/rhct.c b/drivers/acpi/riscv/rhct.c
index caa2c16e1697..8f3f38c64a88 100644
--- a/drivers/acpi/riscv/rhct.c
+++ b/drivers/acpi/riscv/rhct.c
@@ -44,10 +44,15 @@ int acpi_get_riscv_isa(struct acpi_table_header *table, unsigned int cpu, const
 	struct acpi_rhct_isa_string *isa_node;
 	struct acpi_table_rhct *rhct;
 	u32 *hart_info_node_offset;
-	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	u32 acpi_cpu_id;
+	int ret;
 
 	BUG_ON(acpi_disabled);
 
+	ret = acpi_get_cpu_uid(cpu, &acpi_cpu_id);
+	if (ret != 0)
+		return ret;
+
 	if (!table) {
 		rhct = acpi_get_rhct();
 		if (!rhct)
diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c
index 34430b68f602..ed72c3d1f796 100644
--- a/drivers/perf/arm_cspmu/arm_cspmu.c
+++ b/drivers/perf/arm_cspmu/arm_cspmu.c
@@ -1107,15 +1107,17 @@ static int arm_cspmu_acpi_get_cpus(struct arm_cspmu *cspmu)
 {
 	struct acpi_apmt_node *apmt_node;
 	int affinity_flag;
+	u32 cpu_uid;
 	int cpu;
+	int ret;
 
 	apmt_node = arm_cspmu_apmt_node(cspmu->dev);
 	affinity_flag = apmt_node->flags & ACPI_APMT_FLAGS_AFFINITY;
 
 	if (affinity_flag == ACPI_APMT_FLAGS_AFFINITY_PROC) {
 		for_each_possible_cpu(cpu) {
-			if (apmt_node->proc_affinity ==
-			    get_acpi_id_for_cpu(cpu)) {
+			ret = acpi_get_cpu_uid(cpu, &cpu_uid);
+			if (ret == 0 && apmt_node->proc_affinity == cpu_uid) {
 				cpumask_set_cpu(cpu, &cspmu->associated_cpus);
 				break;
 			}
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 4d2f0bed7a06..035094a55f18 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -324,6 +324,19 @@ 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)
+ * @uid: Pointer to store the ACPI Processor UID (valid only on successful return)
+ *
+ * Return: 0 on successful retrieval (the ACPI Processor ID is stored in *uid);
+ *         -EINVAL if the CPU number is invalid or out of range;
+ *         -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);
 #endif
-- 
2.17.1

Re: [PATCH v6 1/3] ACPI: Rename get_acpi_id_for_cpu() to acpi_get_cpu_uid() on non-x86

[Jonathan Cameron]

On Thu, 12 Mar 2026 15:23:14 +0800
Chengwen Feng <fengchengwen@huawei.com> wrote:

> To unify the CPU ACPI ID retrieval interface across architectures,
> rename the existing get_acpi_id_for_cpu() function to
> acpi_get_cpu_uid() on arm64/riscv/loongarch platforms.
> 
> This is a pure rename with no functional change, preparing for a

It's not just a rename.  This should mention that the addition of error
checks and hence the resulting signature change.

> consistent ACPI Processor UID retrieval interface across all ACPI-enabled
> platforms.
> 
> Note: Move the ARM64-specific get_cpu_for_acpi_id() implementation to
>       arch/arm64/kernel/acpi_numa.c to fix compilation errors from
>       circular header dependencies introduced by the rename.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
From a reread, a few minor style consistency things inline.

> ---
>  arch/arm64/include/asm/acpi.h      | 16 +---------
>  arch/arm64/kernel/acpi.c           | 16 ++++++++++
>  arch/arm64/kernel/acpi_numa.c      | 15 ++++++++++
>  arch/loongarch/include/asm/acpi.h  |  5 ----
>  arch/loongarch/kernel/acpi.c       |  9 ++++++
>  arch/riscv/include/asm/acpi.h      |  4 ---
>  arch/riscv/kernel/acpi.c           | 16 ++++++++++
>  arch/riscv/kernel/acpi_numa.c      |  8 +++--
>  drivers/acpi/pptt.c                | 47 +++++++++++++++++++++---------
>  drivers/acpi/riscv/rhct.c          |  7 ++++-
>  drivers/perf/arm_cspmu/arm_cspmu.c |  6 ++--
>  include/linux/acpi.h               | 13 +++++++++
>  12 files changed, 120 insertions(+), 42 deletions(-)

> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index af90128cfed5..984a11788265 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -458,3 +458,19 @@ int acpi_unmap_cpu(int cpu)
>  }
>  EXPORT_SYMBOL(acpi_unmap_cpu);
>  #endif /* CONFIG_ACPI_HOTPLUG_CPU */
> +
> +int acpi_get_cpu_uid(unsigned int cpu, u32 *uid)
> +{
> +	struct acpi_madt_generic_interrupt *gicc;
> +
> +	if (cpu >= nr_cpu_ids)
> +		return -EINVAL;
> +
> +	gicc = acpi_cpu_get_madt_gicc(cpu);
> +	if (gicc == NULL)

Seems local style for null pointer checks is
	if (!gicc)
Just for consistency we should follow that.

> +		return -ENODEV;
> +
> +	*uid = gicc->uid;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(acpi_get_cpu_uid);
> diff --git a/arch/arm64/kernel/acpi_numa.c b/arch/arm64/kernel/acpi_numa.c
> index 2465f291c7e1..56e2e486e49b 100644
> --- a/arch/arm64/kernel/acpi_numa.c
> +++ b/arch/arm64/kernel/acpi_numa.c
> @@ -34,6 +34,21 @@ int __init acpi_numa_get_nid(unsigned int cpu)
>  	return acpi_early_node_map[cpu];
>  }
>  
> +int get_cpu_for_acpi_id(u32 uid)
> +{
> +	u32 cpu_uid;
> +	int cpu;
> +	int ret;
> +
> +	for (cpu = 0; cpu < nr_cpu_ids; cpu++) {

Given more recent acceptance of the following perhaps it is neater here.

	for (int cpu = 0; cpu < nr_cpu_ids; cpu++) {

Amazingly there aren't any for loops in this file so we can do what we
like from a consistency point of view.


> +		ret = acpi_get_cpu_uid(cpu, &cpu_uid);
> +		if (ret == 0 && uid == cpu_uid)
> +			return cpu;
> +	}
> +
> +	return -EINVAL;
> +}
> +
>  static int __init acpi_parse_gicc_pxm(union acpi_subtable_headers *header,
>  				      const unsigned long end)
>  {


> diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
> index 71698ee11621..bde810d02c4f 100644
> --- a/arch/riscv/kernel/acpi.c
> +++ b/arch/riscv/kernel/acpi.c
> @@ -337,3 +337,19 @@ int raw_pci_write(unsigned int domain, unsigned int bus,
>  }
>  
>  #endif	/* CONFIG_PCI */
> +
> +int acpi_get_cpu_uid(unsigned int cpu, u32 *uid)
> +{
> +	struct acpi_madt_rintc *rintc;
> +
> +	if (cpu >= nr_cpu_ids)
> +		return -EINVAL;
> +
> +	rintc = acpi_cpu_get_madt_rintc(cpu);
> +	if (rintc == NULL)

Similar to above. Local style for NULL checks is
	if (!rintc)
so this should follow that.
> +		return -ENODEV;
> +
> +	*uid = rintc->uid;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(acpi_get_cpu_uid);
> diff --git a/arch/riscv/kernel/acpi_numa.c b/arch/riscv/kernel/acpi_numa.c
> index 130769e3a99c..cd8adc9857e3 100644
> --- a/arch/riscv/kernel/acpi_numa.c
> +++ b/arch/riscv/kernel/acpi_numa.c
> @@ -37,11 +37,15 @@ static int __init acpi_numa_get_nid(unsigned int cpu)
>  
>  static inline int get_cpu_for_acpi_id(u32 uid)
>  {
> +	u32 cpu_uid;
>  	int cpu;
> +	int ret;
>  
> -	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
> -		if (uid == get_acpi_id_for_cpu(cpu))
> +	for (cpu = 0; cpu < nr_cpu_ids; cpu++) {

Can pull the int into the loop her as well.

> +		ret = acpi_get_cpu_uid(cpu, &cpu_uid);
> +		if (ret == 0 && uid == cpu_uid)
>  			return cpu;
> +	}
>  
>  	return -EINVAL;
>  }
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index de5f8c018333..d034a217e85b 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c

>  static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
>  {
>  	struct acpi_table_header *table;
> -	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> +	u32 acpi_cpu_id;
>  	struct acpi_pptt_processor *cpu_node = NULL;
>  	int ret = -ENOENT;
>  
> +	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
> +		return -ENOENT;
> +
>  	table = acpi_get_pptt();
>  	if (!table)
>  		return -ENOENT;
> @@ -651,7 +661,8 @@ static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
>   * in the PPTT. Errors caused by lack of a PPTT table, or otherwise, return 0
>   * indicating we didn't find any cache levels.
>   *
> - * Return: -ENOENT if no PPTT table or no PPTT processor struct found.
> + * Return: -ENOENT if no PPTT table, can't get CPU's ACPI Process UID or no PPTT
> + *	   processor struct found.
>   *	   0 on success.
>   */
>  int acpi_get_cache_info(unsigned int cpu, unsigned int *levels,
> @@ -671,7 +682,8 @@ int acpi_get_cache_info(unsigned int cpu, unsigned int *levels,
>  
>  	pr_debug("Cache Setup: find cache levels for CPU=%d\n", cpu);
>  
> -	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> +	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id))
> +		return -ENOENT;
I'd put a blank line here (similar to the code you added just above).
>  	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
>  	if (!cpu_node)
>  		return -ENOENT;
> @@ -780,8 +792,9 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
>   * It may not exist in single CPU systems. In simple multi-CPU systems,
>   * it may be equal to the package topology level.
>   *
> - * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be found
> - * or there is no toplogy level above the CPU..
> + * Return: -ENOENT if the PPTT doesn't exist, can't get CPU's ACPI
> + * Processor UID, the CPU cannot be found or there is no toplogy level
> + * above the CPU.
>   * Otherwise returns a value which represents the package for this CPU.
>   */
>  
> @@ -797,7 +810,8 @@ int find_acpi_cpu_topology_cluster(unsigned int cpu)
>  	if (!table)
>  		return -ENOENT;
>  
> -	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> +	if (acpi_get_cpu_uid(cpu, &acpi_cpu_id) != 0)
> +		return -ENOENT;
Again, I'd put a blank line here.

>  	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
>  	if (!cpu_node || !cpu_node->parent)
>  		return -ENOENT;
> @@ -872,7 +886,8 @@ static void acpi_pptt_get_child_cpus(struct acpi_table_header *table_hdr,
>  	cpumask_clear(cpus);
>  
>  	for_each_possible_cpu(cpu) {
> -		acpi_id = get_acpi_id_for_cpu(cpu);
> +		if (acpi_get_cpu_uid(cpu, &acpi_id) != 0)
> +			continue;
and here.
>  		cpu_node = acpi_find_processor_node(table_hdr, acpi_id);
>  
>  		while (cpu_node) {

Re: [PATCH v6 1/3] ACPI: Rename get_acpi_id_for_cpu() to acpi_get_cpu_uid() on non-x86

[fengchengwen]

On 3/12/2026 7:07 PM, Jonathan Cameron wrote:
> On Thu, 12 Mar 2026 15:23:14 +0800
> Chengwen Feng <fengchengwen@huawei.com> wrote:
> 
>> To unify the CPU ACPI ID retrieval interface across architectures,
>> rename the existing get_acpi_id_for_cpu() function to
>> acpi_get_cpu_uid() on arm64/riscv/loongarch platforms.
>>
>> This is a pure rename with no functional change, preparing for a
> 
> It's not just a rename.  This should mention that the addition of error
> checks and hence the resulting signature change.

Sorry for overlooking this, it has already been fixed in v7.
And v7 also fix below review comments.

Thanks

> 
>> consistent ACPI Processor UID retrieval interface across all ACPI-enabled
>> platforms.
>>
>> Note: Move the ARM64-specific get_cpu_for_acpi_id() implementation to
>>       arch/arm64/kernel/acpi_numa.c to fix compilation errors from
>>       circular header dependencies introduced by the rename.
>>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
>> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> From a reread, a few minor style consistency things inline.
> 

...

> 

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

[Chengwen Feng]

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

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

[Jonathan Cameron]

On Thu, 12 Mar 2026 15:23:15 +0800
Chengwen Feng <fengchengwen@huawei.com> 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>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

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

[Peter Zijlstra]

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.

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

[fengchengwen]

On 3/12/2026 7:02 PM, Peter Zijlstra wrote:
> 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.

This is indeed an issue, it has been fixed in v7 (by treating CPU_ACPIID_INVALID as an error).

Thanks

> 
> 

[PATCH v6 3/3] PCI/TPH: Fix get cpu steer-tag fail on ARM64 platform

[Chengwen Feng]

pcie_tph_get_cpu_st() is broken on ARM64:
1. pcie_tph_get_cpu_st() passes cpu_uid to the PCI ACPI DSM method.
   cpu_uid should be the ACPI Processor UID [1].
2. In BNXT, pcie_tph_get_cpu_st() is passed a cpu_uid obtained via
   cpumask_first(irq->cpu_mask) - the logical CPU ID of a CPU core,
   generated and managed by kernel (e.g., [0,255] for a system  with 256
   logical CPU cores).
3. On ARM64 platforms, ACPI assigns Processor UID to cores listed in the
   MADT table, and this UID may not match the kernel's logical CPU ID.
   When this occurs, the mismatch results in the wrong CPU steer-tag.
4. On AMD x86 the logical CPU ID is identical to the ACPI Processor UID
   so the mismatch is not seen.

Resolution:
1. Use acpi_get_cpu_uid() in pcie_tph_get_cpu_st() to translate from
   logical CPU ID to ACPI Processor UID needed for the DSM call.
2. Rename pcie_tpu_get_cpu_st() parameter from cpu_uid to cpu to
   reflect that it is a logical CPU_ID.

[1] According to ECN_TPH-ST_Revision_20200924
    (https://members.pcisig.com/wg/PCI-SIG/document/15470), the input
    is defined as: "If the target is a processor, then this field
    represents the ACPI Processor UID of the processor as specified in
    the MADT. If the target is a processor container, then this field
    represents the ACPI Processor UID of the processor container as
    specified in the PPTT."

Fixes: d2e8a34876ce ("PCI/TPH: Add Steering Tag support")
Cc: stable@vger.kernel.org
Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
---
 Documentation/PCI/tph.rst |  4 ++--
 drivers/pci/tph.c         | 16 +++++++++++-----
 include/linux/pci-tph.h   |  4 ++--
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/Documentation/PCI/tph.rst b/Documentation/PCI/tph.rst
index e8993be64fd6..b6cf22b9bd90 100644
--- a/Documentation/PCI/tph.rst
+++ b/Documentation/PCI/tph.rst
@@ -79,10 +79,10 @@ To retrieve a Steering Tag for a target memory associated with a specific
 CPU, use the following function::
 
   int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type type,
-                          unsigned int cpu_uid, u16 *tag);
+                          unsigned int cpu, u16 *tag);
 
 The `type` argument is used to specify the memory type, either volatile
-or persistent, of the target memory. The `cpu_uid` argument specifies the
+or persistent, of the target memory. The `cpu` argument specifies the
 CPU where the memory is associated to.
 
 After the ST value is retrieved, the device driver can use the following
diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
index ca4f97be7538..b67c9ad14bda 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -236,21 +236,27 @@ static int write_tag_to_st_table(struct pci_dev *pdev, int index, u16 tag)
  * with a specific CPU
  * @pdev: PCI device
  * @mem_type: target memory type (volatile or persistent RAM)
- * @cpu_uid: associated CPU id
+ * @cpu: associated CPU id
  * @tag: Steering Tag to be returned
  *
  * Return the Steering Tag for a target memory that is associated with a
- * specific CPU as indicated by cpu_uid.
+ * specific CPU as indicated by cpu.
  *
  * Return: 0 if success, otherwise negative value (-errno)
  */
 int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type mem_type,
-			unsigned int cpu_uid, u16 *tag)
+			unsigned int cpu, u16 *tag)
 {
 #ifdef CONFIG_ACPI
 	struct pci_dev *rp;
 	acpi_handle rp_acpi_handle;
 	union st_info info;
+	u32 cpu_uid;
+	int ret;
+
+	ret = acpi_get_cpu_uid(cpu, &cpu_uid);
+	if (ret != 0)
+		return ret;
 
 	rp = pcie_find_root_port(pdev);
 	if (!rp || !rp->bus || !rp->bus->bridge)
@@ -265,9 +271,9 @@ int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type mem_type,
 
 	*tag = tph_extract_tag(mem_type, pdev->tph_req_type, &info);
 
-	pci_dbg(pdev, "get steering tag: mem_type=%s, cpu_uid=%d, tag=%#04x\n",
+	pci_dbg(pdev, "get steering tag: mem_type=%s, cpu=%d, tag=%#04x\n",
 		(mem_type == TPH_MEM_TYPE_VM) ? "volatile" : "persistent",
-		cpu_uid, *tag);
+		cpu, *tag);
 
 	return 0;
 #else
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
index ba28140ce670..be68cd17f2f8 100644
--- a/include/linux/pci-tph.h
+++ b/include/linux/pci-tph.h
@@ -25,7 +25,7 @@ int pcie_tph_set_st_entry(struct pci_dev *pdev,
 			  unsigned int index, u16 tag);
 int pcie_tph_get_cpu_st(struct pci_dev *dev,
 			enum tph_mem_type mem_type,
-			unsigned int cpu_uid, u16 *tag);
+			unsigned int cpu, u16 *tag);
 void pcie_disable_tph(struct pci_dev *pdev);
 int pcie_enable_tph(struct pci_dev *pdev, int mode);
 u16 pcie_tph_get_st_table_size(struct pci_dev *pdev);
@@ -36,7 +36,7 @@ static inline int pcie_tph_set_st_entry(struct pci_dev *pdev,
 { return -EINVAL; }
 static inline int pcie_tph_get_cpu_st(struct pci_dev *dev,
 				      enum tph_mem_type mem_type,
-				      unsigned int cpu_uid, u16 *tag)
+				      unsigned int cpu, u16 *tag)
 { return -EINVAL; }
 static inline void pcie_disable_tph(struct pci_dev *pdev) { }
 static inline int pcie_enable_tph(struct pci_dev *pdev, int mode)
-- 
2.17.1