On 11/17/2022 12:37 AM, Vishal Verma wrote:
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/

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: <sta...@vger.kernel.org>
Cc: Rafael J. Wysocki <raf...@kernel.org>
Cc: Liu Shixin <liushix...@huawei.com>
Cc: Dan Williams <dan.j.willi...@intel.com>
Cc: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Reported-by: Chris Piper <chris.d.pi...@intel.com>
Signed-off-by: Vishal Verma <vishal.l.ve...@intel.com>

Acked-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>

  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)

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