[PATCH v2 2/2] ACPI: HMAT: Fix initiator registration for single-initiator systems

From: Vishal Verma
Date: Wed Nov 16 2022 - 18:43:08 EST


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.

Cc: <stable@xxxxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rafael@xxxxxxxxxx>
Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: Chris Piper <chris.d.piper@xxxxxxxxx>
Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
---
drivers/acpi/numa/hmat.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index 144a84f429ed..6cceca64a6bc 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -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)

--
2.38.1