[PATCH v7 6/7] x86/amd_node: Restrict SMN setup to AMD CPUs

[Lin Wang]

amd_smn_init() also runs on Hygon because Hygon sets X86_FEATURE_ZEN.
It reserves config space on the matching host-bridge roots and groups
them by the CPU-derived node count. Hygon DF nodes are enumerated by
PCI ID, CPU NodeIds are sparse, and the nodes in a socket share one SMN
ingress, so the resulting root map is wrong on Hygon. These reservations
also prevent the Hygon node layer from claiming roots for its own
node-to-root mapping.

The preceding patches remove the Hygon matches from amd64_edac and ATL.
This change also requires "hwmon: (k10temp) Stop matching Hygon devices".
The remaining users match AMD PCI IDs or check for an AMD CPU.
With these changes in place, no in-tree Hygon driver uses the AMD
SMN accessors.

Restrict SMN setup and root discovery to AMD CPUs.

Signed-off-by: Lin Wang <wanglin@xxxxxxxxxxxxxx>
---

Notes (hygon-node-deps):
    Depends on commit 08e6615c909b ("hwmon: (k10temp) Stop matching Hygon
    devices") in hwmon-next, which is not in mainline yet. It must be merged
    before this patch.

 arch/x86/kernel/amd_node.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c
index b7926ba3610a..c36b410d04a4 100644
--- a/arch/x86/kernel/amd_node.c
+++ b/arch/x86/kernel/amd_node.c
@@ -229,8 +229,7 @@ static struct pci_dev *get_next_root(struct pci_dev *root)
 		if (root->devfn)
 			continue;
 
-		if (root->vendor != PCI_VENDOR_ID_AMD &&
-		    root->vendor != PCI_VENDOR_ID_HYGON)
+		if (root->vendor != PCI_VENDOR_ID_AMD)
 			continue;
 
 		break;
@@ -253,6 +252,9 @@ static int __init amd_smn_init(void)
 	u16 count, num_roots, roots_per_node, node, num_nodes;
 	struct pci_dev *root __free(pci_dev_put) = NULL;
 
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
+		return 0;
+
 	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
 		return 0;
 
-- 
2.43.0