linux-kernel - [PATCH 1/2] powerpc/nodes: Ensure enough nodes avail for operations

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Message-Id: <d62dd6c7-7676-5fe0-4f63-baada9213908@linux.vnet.ibm.com>
Date:   Mon, 18 Sep 2017 13:28:33 -0500
From:   Michael Bringmann <mwb@...ux.vnet.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        John Allen <jallen@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>
Subject: [PATCH 1/2] powerpc/nodes: Ensure enough nodes avail for operations

powerpc/nodes: On systems like PowerPC which allow 'hot-add' of CPU
or memory resources, it may occur that the new resources are to be
inserted into nodes that were not used for these resources at bootup.
In the kernel, any node that is used must be defined and initialized
at boot.

This patch extracts the value of the lowest domain level (number of
allocable resources) from the "rtas" device tree property
"ibm,current-associativity-domains" or the device tree property
"ibm,max-associativity-domains" to use as the maximum number of nodes
to setup as possibly available in the system.  This new setting will
override the instruction,

    nodes_and(node_possible_map, node_possible_map, node_online_map);

presently seen in the function arch/powerpc/mm/numa.c:initmem_init().

If the property is not present at boot, no operation will be performed
to define or enable additional nodes.

Signed-off-by: Michael Bringmann <mwb@...ux.vnet.ibm.com>
---
 arch/powerpc/mm/numa.c |   47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index ec098b3..b385cd0 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -892,6 +892,51 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
 	NODE_DATA(nid)->node_spanned_pages = spanned_pages;
 }
 
+static void __init node_associativity_setup(void)
+{
+	struct device_node *rtas;
+
+	rtas = of_find_node_by_path("/rtas");
+	if (rtas) {
+		const __be32 *prop;
+		u32 len, entries, numnodes, i;
+
+		prop = of_get_property(rtas,
+					"ibm,current-associativity-domains", &len);
+		if (!prop || len < sizeof(unsigned int)) {
+			prop = of_get_property(rtas,
+					"ibm,max-associativity-domains", &len);
+			goto endit;
+		}
+
+		entries = of_read_number(prop++, 1);
+
+		if (len < (entries * sizeof(unsigned int)))
+			goto endit;
+
+		if ((0 <= min_common_depth) && (min_common_depth <= (entries-1)))
+			entries = min_common_depth;
+		else
+			entries -= 1;
+
+		numnodes = of_read_number(&prop[entries], 1);
+
+		printk(KERN_INFO "numa: Nodes = %d (mcd = %d)\n", numnodes,
+			min_common_depth);
+
+		for (i = 0; i < numnodes; i++) {
+			if (!node_possible(i)) {
+				setup_node_data(i, 0, 0);
+				node_set(i, node_possible_map);
+			}
+		}
+	}
+
+endit:
+	if (rtas)
+		of_node_put(rtas);
+}
+
 void __init initmem_init(void)
 {
 	int nid, cpu;
@@ -911,6 +956,8 @@ void __init initmem_init(void)
 	 */
 	nodes_and(node_possible_map, node_possible_map, node_online_map);
 
+	node_associativity_setup();
+
 	for_each_online_node(nid) {
 		unsigned long start_pfn, end_pfn;