FAILED: patch "[PATCH] ACPI: HMAT: Fix initiator registration for single-initiator" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

48d4180939e1 ("ACPI: HMAT: Fix initiator registration for single-initiator systems") 14f16d47561b ("ACPI: HMAT: remove unnecessary variable initialization")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 48d4180939e12c4bd2846f984436d895bb9699ed Mon Sep 17 00:00:00 2001
From: Vishal Verma <[email protected]>
Date: Wed, 16 Nov 2022 16:37:37 -0700
Subject: [PATCH] ACPI: HMAT: Fix initiator registration for single-initiator
systems

In a system with a single initiator node, and one or more memory-only 'target' nodes, the memory-only node(s) would fail to register their initiator node correctly. i.e. in sysfs:

  # ls /sys/devices/system/node/node0/access0/targets/
  node0

Where as the correct behavior should be:

  # ls /sys/devices/system/node/node0/access0/targets/
  node0 node1

This happened because hmat_register_target_initiators() uses list_sort() to sort the initiator list, but the sort comparision function (initiator_cmp()) is overloaded to also set the node mask's bits.

In a system with a single initiator, the list is singular, and list_sort elides the comparision helper call. Thus the node mask never gets set, and the subsequent search for the best initiator comes up empty.

Add a new helper to consume the sorted initiator list, and generate the nodemask, decoupling it from the overloaded initiator_cmp() comparision callback. This prevents the singular list corner case naturally, and makes the code easier to follow as well.

index 144a84f429ed..6cceca64a6bc 100644
@@ -562,17 +562,26 @@ static int initiator_cmp(void *priv, const struct list_head *a,
 {
 	struct memory_initiator *ia;
 	struct memory_initiator *ib;
-	unsigned long *p_nodes = priv;
 
 	ia = list_entry(a, struct memory_initiator, node);
 	ib = list_entry(b, struct memory_initiator, node);
 
-	set_bit(ia->processor_pxm, p_nodes);
-	set_bit(ib->processor_pxm, p_nodes);
-
 	return ia->processor_pxm - ib->processor_pxm;
 }
 
+static int initiators_to_nodemask(unsigned long *p_nodes)
+{
+	struct memory_initiator *initiator;
+
+	if (list_empty(&initiators))
+		return -ENXIO;
+
+	list_for_each_entry(initiator, &initiators, node)
+		set_bit(initiator->processor_pxm, p_nodes);
+
+	return 0;
+}
+
 static void hmat_register_target_initiators(struct memory_target *target)
 {
 	static DECLARE_BITMAP(p_nodes, MAX_NUMNODES);

@@ -609,7 +618,10 @@ static void hmat_register_target_initiators(struct memory_target *target)
 	 * initiators.
 	 */
 	bitmap_zero(p_nodes, MAX_NUMNODES);
-	list_sort(p_nodes, &initiators, initiator_cmp);
+	list_sort(NULL, &initiators, initiator_cmp);
+	if (initiators_to_nodemask(p_nodes) < 0)
+		return;
+
 	if (!access0done) {
 		for (i = WRITE_LATENCY; i <= READ_BANDWIDTH; i++) {
 			loc = localities_types[i];

@@ -643,7 +655,9 @@ static void hmat_register_target_initiators(struct memory_target *target)
 
 	/* Access 1 ignores Generic Initiators */
 	bitmap_zero(p_nodes, MAX_NUMNODES);
-	list_sort(p_nodes, &initiators, initiator_cmp);
+	if (initiators_to_nodemask(p_nodes) < 0)
+		return;
+
 	for (i = WRITE_LATENCY; i <= READ_BANDWIDTH; i++) {
 		loc = localities_types[i];
 		if (!loc)