[PATCH v3 0/6] x86/hygon: Add Family 0x18 DF node enumeration and SMN access

[Lin Wang]

Hygon Family 0x18 systems expose Data Fabric (DF) devices in a layout
that cannot be handled by the AMD fixed-slot node model.

AMD node enumeration relies on DF nodes being visible at fixed PCI
slots 00:18.x through 00:1f.x.  Hygon Family 0x18 instead enumerates
DF instances by PCI device ID at platform-assigned slots.  The node
identity is provided by DF registers, not by the PCI slot number:

  - F1x200 provides socket identity and SocketPresent.
  - F5x180 provides the real DFID on models which need it.
  - CPUID 0x8000001E reports sparse phys_node_id values across sockets.
  - SMN root devices are shared per socket rather than per DF node.

This series adds a Hygon-specific node implementation in
arch/x86/kernel/hygon_node.c.  The Hygon code owns DF enumeration,
node identity, CPU-to-DF-node translation, DF F3/F4 lookup, SMN access,
and the optional SMN debugfs interface.

The AMD-side changes are limited to vendor gating and access-path
hardening:

  - amd_nb.c no longer runs AMD NB framework initialization for Hygon.
  - amd_node.c no longer reserves Hygon SMN root devices from the AMD
    SMN init path.
  - __amd_smn_rw() checks smn_exclusive before indexing amd_roots[],
    so callers that reach the AMD SMN path before initialization get
    -ENODEV rather than dereferencing a NULL root array.

amd_get_mmconfig_range() is intentionally unchanged because it reads
the shared MSR_FAM10H_MMIO_CONF_BASE path used by x86 PCI/PnP code.

No intended behavioral change for AMD systems: the vendor-gating changes
only remove Hygon from AMD-only init paths, and the AMD CPU paths they
now exclusively gate are otherwise unchanged.  The patch 3 SMN access
hardening does not affect AMD SMN access after successful initialization.

The Hygon node cache is built once from fs_initcall:

  1. Enumerate DF misc (F3) devices by Hygon PCI ID.
  2. Read node identity from DF registers.
  3. Validate the enumerated socket set against SocketPresent.
  4. Sort nodes into a dense software order:
       CDD nodes first, sorted by socket and DFID;
       IOD nodes afterwards, sorted by socket and DFID.
  5. Enable CPU-to-DF translation when CPUID NodesPerProcessor matches
     the enumerated CDD count per socket.
  6. Set up Hygon SMN roots and optional debugfs.

The public API is provided by <asm/hygon/node.h>.  It exposes validated
topology and lookup helpers, not model-range helpers.  Model matching is
kept private to the Hygon node implementation through the internal DF
identity table.  Consumers that need their own per-model behavior should
use standard x86_cpu_id matching with driver_data.

When CONFIG_HYGON_NODE=n, the header provides static-inline stubs
returning 0, NULL, or -ENODEV, so consumers do not need local #ifdefs.

SMN access uses the same index/data PCI config-space transaction model
as amd_smn_read/write(), serialized by a Hygon-local mutex.  The
Hygon-specific part is the binding from dense DF node id to the correct
socket-local SMN root.

Patch layout:

  [1/6] pci_ids:      Add Hygon Family 0x18 DF F3/F4 device IDs.
  [2/6] x86/amd_nb:   Restrict AMD NB framework init to AMD vendor.
  [3/6] x86/amd_node: Restrict AMD SMN root enumeration to AMD vendor
                      and harden AMD SMN access before root indexing.
  [4/6] x86/hygon:    Add Hygon DF node enumeration, node cache, lookup
                      API, and CPU-to-DF translation.
  [5/6] x86/hygon:    Add Hygon SMN read/write support.
  [6/6] x86/hygon:    Add optional Hygon SMN debugfs support.

Patch 5 depends on patch 3 at runtime: without the AMD SMN vendor gate,
amd_smn_init() can reserve Hygon root config space before the Hygon SMN
setup runs.  Patch 6 is optional debugfs support and can be reverted
independently.

Tested on:

  - Hygon Family 0x18 Model 0x04, 4 sockets, 16 CDD + 4 IOD
  - Hygon Family 0x18 Model 0x04, 2 sockets, 8 CDD + 2 IOD
  - Hygon Family 0x18 Model 0x07, 2 sockets, 12 CDD + 4 IOD

Verified:

  - Boot and initcall ordering.
  - DF identity register reads.
  - SocketPresent validation against enumerated sockets.
  - CPU-to-DF-node translation.
  - CPU-to-DF-node translation with maxcpus=4 on Model 0x04.
  - SMN read/write on representative addresses.
  - AMD-only and Hygon-enabled build configurations.
  - x86_64 defconfig and allyesconfig sanity builds.

Changes since RFC v2:

  - Drop the vendor-neutral registration interfaces from amd_nb.c and
    amd_node.c.
  - Move Hygon DF enumeration, node identity, CPU-to-DF translation,
    SMN access, and debugfs into Hygon-specific code.
  - Restrict AMD NB and AMD SMN initialization paths to AMD vendor.
  - Harden the AMD SMN access path before indexing amd_roots[].
  - Replace the online-CPU-derived nid map with CPUID NodeId based
    CPU-to-DF translation.
  - Keep supported-model matching private to the Hygon node module.
  - Limit this series to Hygon Family 0x18 models 0x04-0x08.
  - Validate DF enumeration completeness against SocketPresent.
  - Add Hygon SMN debugfs topology output.

Sashiko review follow-up:

  RFC v2 also received a Sashiko automated review.  The changes listed
  above cover its main design findings; patch 3 additionally reorders
  __amd_smn_rw() to check smn_exclusive before indexing amd_roots[].
  The remaining low-level SMN index/data and selector-style debugfs
  behavior stays aligned with the existing AMD SMN model, while
  Hygon-specific discovery and topology binding live in hygon_node.c.

  Patch-level nits are handled in the individual commit messages; patch
  1 keeps the DF F3/F4 IDs as Hygon-prefixed pci_ids.h entries because
  future Hygon DF consumers may share them.

Links:

  RFC v1:
    https://lore.kernel.org/all/20260402111515.1155505-1-wanglin@xxxxxxxxxxxxxx/

  RFC v2:
    https://lore.kernel.org/all/20260423060420.1785357-1-wanglin@xxxxxxxxxxxxxx/

  Sashiko review of RFC v2:
    https://sashiko.dev/#/patchset/20260423060420.1785357-1-wanglin@xxxxxxxxxxxxxx/

Lin Wang (6):
  pci_ids: Add Hygon Family 0x18 DF F3/F4 device IDs
  x86/amd_nb: Restrict NB framework init to AMD vendor
  x86/amd_node: Restrict SMN root enumeration to AMD vendor
  x86/hygon: Add Family 0x18 DF node enumeration
  x86/hygon: Add Family 0x18 SMN access
  x86/hygon: Add SMN debugfs interface

 .../admin-guide/kernel-parameters.txt         |    8 +
 MAINTAINERS                                   |    3 +
 arch/x86/Kconfig                              |    4 +
 arch/x86/include/asm/hygon/node.h             |  205 +++
 arch/x86/kernel/Makefile                      |    1 +
 arch/x86/kernel/amd_nb.c                      |    6 +-
 arch/x86/kernel/amd_node.c                    |   23 +-
 arch/x86/kernel/hygon_node.c                  | 1340 +++++++++++++++++
 include/linux/pci_ids.h                       |    6 +
 9 files changed, 1584 insertions(+), 12 deletions(-)
 create mode 100644 arch/x86/include/asm/hygon/node.h
 create mode 100644 arch/x86/kernel/hygon_node.c

base-commit: 0e35b9b6ec0ffcc5e23cbdec09f5c622ad532b53
--
2.43.0