On 3/6/2026 6:01 PM, Jonathan Cameron wrote:

On Fri, 6 Mar 2026 10:19:17 +0800
Chengwen Feng [off-list ref] wrote:

quoted

Currently the pcie_tph_get_cpu_st() has an issue on ARM64 platform:
1. The pcie_tph_get_cpu_st() function directly uses cpu_uid as the input
   parameter to call the PCI ACPI DSM method. According to the DSM
   definition, the input value should be the ACPI Processor UID (see [1]
   for details).
2. In the Broadcom driver implementation [2] (which invokes
   pcie_tph_get_cpu_st()), cpu_uid is obtained via
   cpumask_first(irq->cpu_mask) - this is 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.
   As a result, the current implementation fails to retrieve the correct
   CPU steer-tag in such cases.
4. The function works on AMD x86 platforms only because the logical CPU
   ID is identical to the ACPI Processor UID on those systems.

This commit fixes it by:
1. For ACPI-enabled platforms, unify the CPU ACPI ID retrieval
   interface:
   - On arm64/riscv/loongarch: Rename existing get_acpi_id_for_cpu() to
     acpi_get_cpu_acpi_id().
   - On x86: Add new acpi_get_cpu_acpi_id() implementation that wraps
     cpu_acpi_id().
2. Update pcie_tph_get_cpu_st() to use acpi_get_cpu_acpi_id(cpu) to get
   valid ACPI Processor UID for DSM calls.
3. Renaming pcie_tph_get_cpu_st()'s input parameter cpu_uid to cpu for
   clarity, as the parameter now represents a logical CPU ID (not a
   UID).

[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."
[2] commit c214410c47d6e ("bnxt_en: Add TPH support in BNXT driver")

Fixes: d2e8a34876ce ("PCI/TPH: Add Steering Tag support")
Cc: stable@vger.kernel.org
Signed-off-by: Chengwen Feng <redacted>

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

Ah. I wasn't clear around that rename suggestion.  Split this into two patches.
1) Rename
2) The new stuff plus x86 implementation.

Hi Jonathan,

All fixes are applied in v4. Please review.

Thanks.

quoted

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.

---
 Documentation/PCI/tph.rst          |  4 ++--
 arch/arm64/include/asm/acpi.h      |  4 ++--
 arch/loongarch/include/asm/acpi.h  |  2 +-
 arch/riscv/include/asm/acpi.h      |  2 +-
 arch/riscv/kernel/acpi_numa.c      |  2 +-
 arch/x86/include/asm/acpi.h        |  2 ++
 arch/x86/kernel/cpu/common.c       |  8 ++++++++
 drivers/acpi/pptt.c                | 16 ++++++++--------
 drivers/acpi/riscv/rhct.c          |  2 +-
 drivers/pci/tph.c                  | 11 ++++++-----
 drivers/perf/arm_cspmu/arm_cspmu.c |  2 +-
 include/linux/pci-tph.h            |  4 ++--
 12 files changed, 35 insertions(+), 24 deletions(-)