Re: [Patch 2/2]: powerpc/hotplug/mm: Fix hot-add memory node assoc

[Reza Arbab]

On Thu, Jun 01, 2017 at 07:36:31PM +1000, Michael Ellerman wrote:
> I don't think that's what the patch does. It just marks 32 (!?) nodes 
> as online. Or if you're talking about reverting 3af229f2071f that 
> leaves you with 256 possible nodes. Both of which are wasteful.

To be clear, with Balbir's set the latter is no longer wasteful.

> The right fix is to make sure any nodes which are present at boot 
> remain in the possible map, even if they don't have memory/CPUs 
> assigned at boot.

I'm still hoping 3af229f2071f could indeed be reverted some day, but 
until then the following would follow your suggestion for our GPU nodes.  
What do you think?

--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -895,6 +895,7 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
void __init initmem_init(void)
{
	int nid, cpu;
+	struct device_node *dn;

	max_low_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
	max_pfn = max_low_pfn;
@@ -911,6 +912,18 @@ void __init initmem_init(void)
	 */
	nodes_and(node_possible_map, node_possible_map, node_online_map);

+	/*
+	 * Consider an ibm,coherent-device-memory node possible. Even though
+	 * it is not online at boot, it may be hotplugged later.
+	 */
+	for_each_compatible_node(dn, NULL, "ibm,coherent-device-memory") {
+		nid = of_node_to_nid_single(dn);
+		if (nid < 0)
+			continue;
+
+		node_set(nid, node_possible_map);
+	}
+
	for_each_online_node(nid) {
		unsigned long start_pfn, end_pfn;


--
Reza Arbab