Commit abdd2a86 authored by Chengwen Feng's avatar Chengwen Feng Committed by Rafael J. Wysocki
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PCI/TPH: Pass ACPI Processor UID to Cache Locality _DSM 

pcie_tph_get_cpu_st() uses the Query Cache Locality Features _DSM [1]
to retrieve the TPH Steering Tag for memory associated with the CPU
identified by its "cpu_uid" parameter, a Linux logical CPU ID.

The _DSM requires an ACPI Processor UID, which pcie_tph_get_cpu_st()
previously assumed was the same as the Linux logical CPU ID. This is
true on x86 but not on arm64, so pcie_tph_get_cpu_st() returned the
wrong Steering Tag, resulting in incorrect TPH functionality on arm64.

Convert the Linux logical CPU ID to the ACPI Processor UID with
acpi_get_cpu_uid() before passing it to the _DSM. Additionally, rename
the pcie_tph_get_cpu_st() parameter from "cpu_uid" to "cpu" to reflect
that it represents a logical CPU ID (not an ACPI Processor 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."

Fixes: d2e8a348 ("PCI/TPH: Add Steering Tag support")
Signed-off-by: default avatarChengwen Feng <fengchengwen@huawei.com>
Reviewed-by: default avatarJonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20260401081640.26875-9-fengchengwen@huawei.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent a7034e9e

Documentation/PCI/tph.rst

+2 −2
Original line number Diff line number Diff line
@@ -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

drivers/pci/tph.c

+11 −5
Original line number Diff line number Diff line
@@ -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

include/linux/pci-tph.h

+2 −2
Original line number Diff line number Diff line
@@ -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)