[PATCH v2 0/3] powerpc/numa: Enable coregroup support on PowerNV

[PATCH v2 0/3] powerpc/numa: Enable coregroup support on PowerNV

[Srikar Dronamraju]

This series prepares cpu_to_coregroup_id() for broader use and enables
coregroup support on PowerNV when firmware exposes the required
associativity information.

The first patch cleans up find_primary_domain_index(). The second makes
cpu_to_coregroup_id() available outside PPC_SPLPAR while preserving the
existing fallback behavior. The final patch detects coregroup support
from the associativity hierarchy and uses it on PowerNV systems.

Changelog from v1: https://lkml.kernel.org/r/20260524010017.140408-1-srikar@linux.ibm.com
- Split into 3 patches
- Handle comments from Christophe Leroy

Srikar Dronamraju (3):
  powerpc/numa: Simplify find_primary_domain_index
  powerpc/numa: Allow cpu_to_coregroup_id without PPC_SPLPAR
  powerpc/numa: Support coregroup on PowerNV

 arch/powerpc/include/asm/topology.h | 15 +++--
 arch/powerpc/mm/numa.c              | 85 ++++++++++++++++++++++-------
 2 files changed, 71 insertions(+), 29 deletions(-)

-- 
2.43.0

[PATCH v2 1/3] powerpc/numa: Simplify find_primary_domain_index

[Srikar Dronamraju]

Initialize the return value once and use a single exit path in
find_primary_domain_index().

This is a small cleanup that keeps the existing behavior unchanged while
making the control flow easier to follow.

Signed-off-by: Srikar Dronamraju <srikar@linux.ibm.com>
---
Changelog from v1:
- Handle comments from Christophe Leroy

 arch/powerpc/mm/numa.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index f4cf3ae036de..c44a80d8fc11 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -432,7 +432,7 @@ static void __init initialize_form2_numa_distance_lookup_table(void)
 
 static int __init find_primary_domain_index(void)
 {
-	int index;
+	int index = -1;
 	struct device_node *root;
 
 	/*
@@ -502,12 +502,9 @@ static int __init find_primary_domain_index(void)
 		distance_ref_points_depth = MAX_DISTANCE_REF_POINTS;
 	}
 
-	of_node_put(root);
-	return index;
-
 err:
 	of_node_put(root);
-	return -1;
+	return index;
 }
 
 static void __init get_n_mem_cells(int *n_addr_cells, int *n_size_cells)
-- 
2.43.0

[PATCH v2 2/3] powerpc/numa: Allow cpu_to_coregroup_id without PPC_SPLPAR

[Srikar Dronamraju]

Make cpu_to_coregroup_id() available outside PPC_SPLPAR so it can be
used by platforms that do not rely on the SPLPAR-specific VPHN path.

Keep the existing fallback behavior by returning the core ID when
coregroup information is unavailable.

Signed-off-by: Srikar Dronamraju <srikar@linux.ibm.com>
---
Changelog from v1:
- Handle comments from Christophe Leroy; Remove extern key word in
  declaration

 arch/powerpc/include/asm/topology.h | 15 +++++++--------
 arch/powerpc/mm/numa.c              | 22 ++++++++++++++++------
 2 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
index 66ed5fe1b718..385715f1ad56 100644
--- a/arch/powerpc/include/asm/topology.h
+++ b/arch/powerpc/include/asm/topology.h
@@ -71,6 +71,7 @@ extern void map_cpu_to_node(int cpu, int node);
 extern void unmap_cpu_from_node(unsigned long cpu);
 #endif /* CONFIG_HOTPLUG_CPU */
 
+int cpu_to_coregroup_id(int cpu);
 #else
 
 static inline int early_cpu_to_node(int cpu) { return 0; }
@@ -107,14 +108,6 @@ static inline void map_cpu_to_node(int cpu, int node) {}
 static inline void unmap_cpu_from_node(unsigned long cpu) {}
 #endif /* CONFIG_HOTPLUG_CPU */
 #endif /* CONFIG_SMP */
-
-#endif /* CONFIG_NUMA */
-
-#if defined(CONFIG_NUMA) && defined(CONFIG_PPC_SPLPAR)
-void find_and_update_cpu_nid(int cpu);
-extern int cpu_to_coregroup_id(int cpu);
-#else
-static inline void find_and_update_cpu_nid(int cpu) {}
 static inline int cpu_to_coregroup_id(int cpu)
 {
 #ifdef CONFIG_SMP
@@ -124,6 +117,12 @@ static inline int cpu_to_coregroup_id(int cpu)
 #endif
 }
 
+#endif /* CONFIG_NUMA */
+
+#if defined(CONFIG_NUMA) && defined(CONFIG_PPC_SPLPAR)
+void find_and_update_cpu_nid(int cpu);
+#else
+static inline void find_and_update_cpu_nid(int cpu) {}
 #endif /* CONFIG_NUMA && CONFIG_PPC_SPLPAR */
 
 #include <asm-generic/topology.h>
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index c44a80d8fc11..9aa71eb7e96b 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1428,6 +1428,21 @@ void find_and_update_cpu_nid(int cpu)
 	pr_debug("%s:%d cpu %d nid %d\n", __func__, __LINE__, cpu, new_nid);
 }
 
+static int topology_update_init(void)
+{
+	topology_inited = 1;
+	return 0;
+}
+device_initcall(topology_update_init);
+
+#else
+static long vphn_get_associativity(unsigned long cpu,
+					__be32 *associativity)
+{
+	return -1;
+}
+#endif /* CONFIG_PPC_SPLPAR */
+
 int cpu_to_coregroup_id(int cpu)
 {
 	__be32 associativity[VPHN_ASSOC_BUFSIZE] = {0};
@@ -1453,10 +1468,5 @@ int cpu_to_coregroup_id(int cpu)
 	return cpu_to_core_id(cpu);
 }
 
-static int topology_update_init(void)
-{
-	topology_inited = 1;
-	return 0;
+	return coregroup_id;
 }
-device_initcall(topology_update_init);
-#endif /* CONFIG_PPC_SPLPAR */
-- 
2.43.0

[PATCH v2 3/3] powerpc/numa: Support coregroup on PowerNV

[Srikar Dronamraju]

Coregroup support on powerpc has so far been limited to PowerVM LPARs.
However, PowerNV can also support coregroups when firmware exposes the
required coregroup information through the associativity hierarchy.

Detect coregroup support by checking whether primary_domain_index is the
penultimate domain in the CPU node's ibm,associativity property. On
PowerNV, a non-penultimate primary_domain_index indicates that firmware
provides an additional level for coregroup information.

This keeps the logic compatible with PowerVM systems, where
primary_domain_index is likewise not the penultimate associativity
domain.

Signed-off-by: Srikar Dronamraju <srikar@linux.ibm.com>
---
Changelog from v1: https://lkml.kernel.org/r/20260524010017.140408-1-srikar@linux.ibm.com
- Handle comments from Christophe Leroy; make code more flat

 arch/powerpc/mm/numa.c | 56 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 46 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 9aa71eb7e96b..e97b624203ea 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -889,12 +889,32 @@ static int __init numa_setup_drmem_lmb(struct drmem_lmb *lmb,
 	return 0;
 }
 
+/*
+ * If hierarchy extends beyond primary_domain_index + 1, then next
+ * level corresponds to coregroup.
+ */
+static int detect_and_enable_coregroup(const __be32 *associativity, int index)
+{
+	if (!associativity || index == -1)
+		goto out;
+
+	index = of_read_number(associativity, 1);
+
+	if (index > primary_domain_index + 1) {
+		coregroup_enabled = 1;
+		return index;
+	}
+out:
+	coregroup_enabled = 0;
+	return -1;
+}
+
 static int __init parse_numa_properties(void)
 {
 	struct device_node *memory, *pci;
-	int default_nid = 0;
-	unsigned long i;
+	int default_nid = 0, index = 0;
 	const __be32 *associativity;
+	unsigned long i;
 
 	if (numa_enabled == 0) {
 		pr_warn("disabled by user\n");
@@ -927,7 +947,6 @@ static int __init parse_numa_properties(void)
 	 */
 	for_each_present_cpu(i) {
 		__be32 vphn_assoc[VPHN_ASSOC_BUFSIZE];
-		struct device_node *cpu;
 		int nid = NUMA_NO_NODE;
 
 		memset(vphn_assoc, 0, VPHN_ASSOC_BUFSIZE * sizeof(__be32));
@@ -935,7 +954,9 @@ static int __init parse_numa_properties(void)
 		if (__vphn_get_associativity(i, vphn_assoc) == 0) {
 			nid = associativity_to_nid(vphn_assoc);
 			initialize_form1_numa_distance(vphn_assoc);
+			index = detect_and_enable_coregroup(vphn_assoc, index);
 		} else {
+			struct device_node *cpu;
 
 			/*
 			 * Don't fall back to default_nid yet -- we will plug
@@ -948,6 +969,7 @@ static int __init parse_numa_properties(void)
 			associativity = of_get_associativity(cpu);
 			if (associativity) {
 				nid = associativity_to_nid(associativity);
+				index = detect_and_enable_coregroup(associativity, index);
 				initialize_form1_numa_distance(associativity);
 			}
 			of_node_put(cpu);
@@ -1445,7 +1467,9 @@ static long vphn_get_associativity(unsigned long cpu,
 
 int cpu_to_coregroup_id(int cpu)
 {
-	__be32 associativity[VPHN_ASSOC_BUFSIZE] = {0};
+	int coregroup_id = cpu_to_core_id(cpu);
+	struct device_node *cpunode = NULL;
+	const __be32 *associativity;
 	int index;
 
 	if (cpu < 0 || cpu > nr_cpu_ids)
@@ -1454,19 +1478,31 @@ int cpu_to_coregroup_id(int cpu)
 	if (!coregroup_enabled)
 		goto out;
 
-	if (!firmware_has_feature(FW_FEATURE_VPHN))
-		goto out;
+	if (firmware_has_feature(FW_FEATURE_VPHN)) {
+		__be32 tmp[VPHN_ASSOC_BUFSIZE] = {0};
 
-	if (vphn_get_associativity(cpu, associativity))
+		if (vphn_get_associativity(cpu, tmp))
+			goto out;
+
+		associativity = tmp;
+
+	} else {
+		cpunode = of_get_cpu_node(cpu, NULL);
+		if (!cpunode)
+			goto out;
+
+		associativity = of_get_associativity(cpunode);
+	}
+	if (!associativity)
 		goto out;
 
 	index = of_read_number(associativity, 1);
 	if (index > primary_domain_index + 1)
-		return of_read_number(&associativity[index - 1], 1);
+		coregroup_id = of_read_number(&associativity[index - 1], 1);
 
 out:
-	return cpu_to_core_id(cpu);
-}
+	if (cpunode)
+		of_node_put(cpunode);
 
 	return coregroup_id;
 }
-- 
2.43.0