powerpc/numa: Online a node if PHB is attached.

In the current design, a numa-node is made online only if that node is
attached to cpu/memory. With this design, if any PCI/IO device is found
to be attached to a numa-node which is not online then the numa-node
id of the corresponding PCI/IO device is set to NUMA_NO_NODE(-1). This
design may negatively impact the performance of PCIe device if the
numa-node assigned to PCIe device is -1 because in such case we may not
be able to accurately calculate the distance between two nodes.

The multi-controller NVMe PCIe disk has an issue with calculating the
node distance if the PCIe NVMe controller is attached to a PCI host
bridge which has numa-node id value set to NUMA_NO_NODE. This patch
helps fix this ensuring that a cpu/memory less numa node is made online
if it's attached to PCI host bridge.
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240517142531.3273464-3-nilay@linux.ibm.com

arch/powerpc/mm/numa.c

@@ -896,7 +896,7 @@ static int __init numa_setup_drmem_lmb(struct drmem_lmb *lmb,
 
 static int __init parse_numa_properties(void)
 {
-	struct device_node *memory;
+	struct device_node *memory, *pci;
 	int default_nid = 0;
 	unsigned long i;
 	const __be32 *associativity;
@@ -1010,6 +1010,18 @@ static int __init parse_numa_properties(void)
 			goto new_range;
 	}
 
+	for_each_node_by_name(pci, "pci") {
+		int nid = NUMA_NO_NODE;
+
+		associativity = of_get_associativity(pci);
+		if (associativity) {
+			nid = associativity_to_nid(associativity);
+			initialize_form1_numa_distance(associativity);
+		}
+		if (likely(nid >= 0) && !node_online(nid))
+			node_set_online(nid);
+	}
+
 	/*
 	 * Now do the same thing for each MEMBLOCK listed in the
 	 * ibm,dynamic-memory property in the

arch/powerpc/platforms/pseries/pci_dlpar.c

@@ -11,6 +11,7 @@
 
 #include <linux/pci.h>
 #include <linux/export.h>
+#include <linux/node.h>
 #include <asm/pci-bridge.h>
 #include <asm/ppc-pci.h>
 #include <asm/firmware.h>
@@ -21,9 +22,22 @@
 struct pci_controller *init_phb_dynamic(struct device_node *dn)
 {
 	struct pci_controller *phb;
+	int nid;
 
 	pr_debug("PCI: Initializing new hotplug PHB %pOF\n", dn);
 
+	nid = of_node_to_nid(dn);
+	if (likely((nid) >= 0)) {
+		if (!node_online(nid)) {
+			if (__register_one_node(nid)) {
+				pr_err("PCI: Failed to register node %d\n", nid);
+			} else {
+				update_numa_distance(dn);
+				node_set_online(nid);
+			}
+		}
+	}
+
 	phb = pcibios_alloc_controller(dn);
 	if (!phb)
 		return NULL;