[PATCH v2] x86/topology: Unify srat_detect_node among amd and hygon
From: Nikola Z. Ivanov
Date: Fri May 15 2026 - 12:34:55 EST
Since the amd and hygon srat_detect_node implementation
is practically identical the code can be shared.
Move the implementation to common.c
and expose it in arch/x86/kernel/cpu/cpu.h for code
in arch/x86/kernel/cpu/ to use.
For intel the separate implementation is kept to
stay consistent with its behavior.
Signed-off-by: Nikola Z. Ivanov <zlatistiv@xxxxxxxxx>
---
Changes since v1:
- Abandon the idea for using the same function for intel,
also move the function to another file and limit its scope to x86
https://lore.kernel.org/all/dcfd7282-f722-46ea-b35c-2ab1333ca0d8@xxxxxxxxx/
arch/x86/kernel/cpu/amd.c | 74 ------------------------------------
arch/x86/kernel/cpu/common.c | 73 +++++++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/cpu.h | 1 +
arch/x86/kernel/cpu/hygon.c | 73 -----------------------------------
arch/x86/kernel/cpu/intel.c | 4 +-
5 files changed, 76 insertions(+), 149 deletions(-)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 2f8e8ff2d000..f317c6bdcf5d 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -277,80 +277,6 @@ static void init_amd_k7(struct cpuinfo_x86 *c)
#endif
}
-#ifdef CONFIG_NUMA
-/*
- * To workaround broken NUMA config. Read the comment in
- * srat_detect_node().
- */
-static int nearby_node(int apicid)
-{
- int i, node;
-
- for (i = apicid - 1; i >= 0; i--) {
- node = __apicid_to_node[i];
- if (node != NUMA_NO_NODE && node_online(node))
- return node;
- }
- for (i = apicid + 1; i < MAX_LOCAL_APIC; i++) {
- node = __apicid_to_node[i];
- if (node != NUMA_NO_NODE && node_online(node))
- return node;
- }
- return first_node(node_online_map); /* Shouldn't happen */
-}
-#endif
-
-static void srat_detect_node(struct cpuinfo_x86 *c)
-{
-#ifdef CONFIG_NUMA
- int cpu = smp_processor_id();
- int node;
- unsigned apicid = c->topo.apicid;
-
- node = numa_cpu_node(cpu);
- if (node == NUMA_NO_NODE)
- node = per_cpu_llc_id(cpu);
-
- /*
- * On multi-fabric platform (e.g. Numascale NumaChip) a
- * platform-specific handler needs to be called to fixup some
- * IDs of the CPU.
- */
- if (x86_cpuinit.fixup_cpu_id)
- x86_cpuinit.fixup_cpu_id(c, node);
-
- if (!node_online(node)) {
- /*
- * Two possibilities here:
- *
- * - The CPU is missing memory and no node was created. In
- * that case try picking one from a nearby CPU.
- *
- * - The APIC IDs differ from the HyperTransport node IDs
- * which the K8 northbridge parsing fills in. Assume
- * they are all increased by a constant offset, but in
- * the same order as the HT nodeids. If that doesn't
- * result in a usable node fall back to the path for the
- * previous case.
- *
- * This workaround operates directly on the mapping between
- * APIC ID and NUMA node, assuming certain relationship
- * between APIC ID, HT node ID and NUMA topology. As going
- * through CPU mapping may alter the outcome, directly
- * access __apicid_to_node[].
- */
- int ht_nodeid = c->topo.initial_apicid;
-
- if (__apicid_to_node[ht_nodeid] != NUMA_NO_NODE)
- node = __apicid_to_node[ht_nodeid];
- /* Pick a nearby node */
- if (!node_online(node))
- node = nearby_node(apicid);
- }
- numa_set_node(cpu, node);
-#endif
-}
-
static void bsp_determine_snp(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_ARCH_HAS_CC_PLATFORM
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a4268c47f2bc..a0d7c7c47153 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2518,6 +2518,79 @@ void cpu_init(void)
load_fixmap_gdt(cpu);
}
+#ifdef CONFIG_NUMA
+/*
+ * To workaround broken NUMA config. Read the comment in
+ * srat_detect_node().
+ */
+static int nearby_node(int apicid)
+{
+ int i, node;
+
+ for (i = apicid - 1; i >= 0; i--) {
+ node = __apicid_to_node[i];
+ if (node != NUMA_NO_NODE && node_online(node))
+ return node;
+ }
+ for (i = apicid + 1; i < MAX_LOCAL_APIC; i++) {
+ node = __apicid_to_node[i];
+ if (node != NUMA_NO_NODE && node_online(node))
+ return node;
+ }
+ return first_node(node_online_map); /* Shouldn't happen */
+}
+#endif
+
+void srat_detect_node(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_NUMA
+ int cpu = smp_processor_id();
+ int node;
+ unsigned int apicid = c->topo.apicid;
+
+ node = numa_cpu_node(cpu);
+ if (node == NUMA_NO_NODE)
+ node = c->topo.llc_id;
+
+ /*
+ * On multi-fabric platform (e.g. Numascale NumaChip) a
+ * platform-specific handler needs to be called to fixup some
+ * IDs of the CPU.
+ */
+ if (x86_cpuinit.fixup_cpu_id)
+ x86_cpuinit.fixup_cpu_id(c, node);
+
+ if (!node_online(node)) {
+ /*
+ * Two possibilities here:
+ *
+ * - The CPU is missing memory and no node was created. In
+ * that case try picking one from a nearby CPU.
+ *
+ * - The APIC IDs differ from the HyperTransport node IDs.
+ * Assume they are all increased by a constant offset, but
+ * in the same order as the HT nodeids. If that doesn't
+ * result in a usable node fall back to the path for the
+ * previous case.
+ *
+ * This workaround operates directly on the mapping between
+ * APIC ID and NUMA node, assuming certain relationship
+ * between APIC ID, HT node ID and NUMA topology. As going
+ * through CPU mapping may alter the outcome, directly
+ * access __apicid_to_node[].
+ */
+ int ht_nodeid = c->topo.initial_apicid;
+
+ if (__apicid_to_node[ht_nodeid] != NUMA_NO_NODE)
+ node = __apicid_to_node[ht_nodeid];
+ /* Pick a nearby node */
+ if (!node_online(node))
+ node = nearby_node(apicid);
+ }
+ numa_set_node(cpu, node);
+#endif
+}
+
#ifdef CONFIG_MICROCODE_LATE_LOADING
/**
* store_cpu_caps() - Store a snapshot of CPU capabilities
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index 5c7a3a71191a..04e73ff9a153 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -65,6 +65,7 @@ extern void check_null_seg_clears_base(struct cpuinfo_x86 *c);
void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, u16 die_id);
void cacheinfo_hygon_init_llc_id(struct cpuinfo_x86 *c);
+void srat_detect_node(struct cpuinfo_x86 *c);
#if defined(CONFIG_AMD_NB) && defined(CONFIG_SYSFS)
struct amd_northbridge *amd_init_l3_cache(int index);
diff --git a/arch/x86/kernel/cpu/hygon.c b/arch/x86/kernel/cpu/hygon.c
index 7f95a74e4c65..a33735094843 100644
--- a/arch/x86/kernel/cpu/hygon.c
+++ b/arch/x86/kernel/cpu/hygon.c
@@ -20,79 +20,6 @@
#include "cpu.h"
-#ifdef CONFIG_NUMA
-/*
- * To workaround broken NUMA config. Read the comment in
- * srat_detect_node().
- */
-static int nearby_node(int apicid)
-{
- int i, node;
-
- for (i = apicid - 1; i >= 0; i--) {
- node = __apicid_to_node[i];
- if (node != NUMA_NO_NODE && node_online(node))
- return node;
- }
- for (i = apicid + 1; i < MAX_LOCAL_APIC; i++) {
- node = __apicid_to_node[i];
- if (node != NUMA_NO_NODE && node_online(node))
- return node;
- }
- return first_node(node_online_map); /* Shouldn't happen */
-}
-#endif
-
-static void srat_detect_node(struct cpuinfo_x86 *c)
-{
-#ifdef CONFIG_NUMA
- int cpu = smp_processor_id();
- int node;
- unsigned int apicid = c->topo.apicid;
-
- node = numa_cpu_node(cpu);
- if (node == NUMA_NO_NODE)
- node = c->topo.llc_id;
-
- /*
- * On multi-fabric platform (e.g. Numascale NumaChip) a
- * platform-specific handler needs to be called to fixup some
- * IDs of the CPU.
- */
- if (x86_cpuinit.fixup_cpu_id)
- x86_cpuinit.fixup_cpu_id(c, node);
-
- if (!node_online(node)) {
- /*
- * Two possibilities here:
- *
- * - The CPU is missing memory and no node was created. In
- * that case try picking one from a nearby CPU.
- *
- * - The APIC IDs differ from the HyperTransport node IDs.
- * Assume they are all increased by a constant offset, but
- * in the same order as the HT nodeids. If that doesn't
- * result in a usable node fall back to the path for the
- * previous case.
- *
- * This workaround operates directly on the mapping between
- * APIC ID and NUMA node, assuming certain relationship
- * between APIC ID, HT node ID and NUMA topology. As going
- * through CPU mapping may alter the outcome, directly
- * access __apicid_to_node[].
- */
- int ht_nodeid = c->topo.initial_apicid;
-
- if (__apicid_to_node[ht_nodeid] != NUMA_NO_NODE)
- node = __apicid_to_node[ht_nodeid];
- /* Pick a nearby node */
- if (!node_online(node))
- node = nearby_node(apicid);
- }
- numa_set_node(cpu, node);
-#endif
-}
-
static void bsp_init_hygon(struct cpuinfo_x86 *c)
{
if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) {
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index f28c0efb7c8f..0c34ec32baec 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -468,7 +468,7 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
}
#endif
-static void srat_detect_node(struct cpuinfo_x86 *c)
+static void srat_detect_node_intel(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_NUMA
unsigned node;
@@ -614,7 +614,7 @@ static void init_intel(struct cpuinfo_x86 *c)
set_cpu_cap(c, X86_FEATURE_PREFER_YMM);
/* Work around errata */
- srat_detect_node(c);
+ srat_detect_node_intel(c);
init_ia32_feat_ctl(c);
--
2.53.0