powerpc/numa: Use cpu node map of first sibling thread

All the sibling threads of a core have to be part of the same node.
To ensure that all the sibling threads map to the same node, always
lookup/update the cpu-to-node map of the first thread in the core.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200129135301.24739-4-srikar@linux.vnet.ibm.com

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 2cb87c9a05441699004238c863d07a8ee46e53f9..518c6dbbccbe4ec05e4e5c156aa8cc6598286ca8 100644 (file)
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -467,15 +467,20 @@ static int of_drconf_to_nid_single(struct drmem_lmb *lmb)
  */
 static int numa_setup_cpu(unsigned long lcpu)
 {
-       int nid = NUMA_NO_NODE;
        struct device_node *cpu;
+       int fcpu = cpu_first_thread_sibling(lcpu);
+       int nid = NUMA_NO_NODE;
 
        /*
         * If a valid cpu-to-node mapping is already available, use it
         * directly instead of querying the firmware, since it represents
         * the most recent mapping notified to us by the platform (eg: VPHN).
+        * Since cpu_to_node binding remains the same for all threads in the
+        * core. If a valid cpu-to-node mapping is already available, for
+        * the first thread in the core, use it.
         */
-       if ((nid = numa_cpu_lookup_table[lcpu]) >= 0) {
+       nid = numa_cpu_lookup_table[fcpu];
+       if (nid >= 0) {
                map_cpu_to_node(lcpu, nid);
                return nid;
        }
@@ -496,6 +501,19 @@ out_present:
        if (nid < 0 || !node_possible(nid))
                nid = first_online_node;
 
+       /*
+        * Update for the first thread of the core. All threads of a core
+        * have to be part of the same node. This not only avoids querying
+        * for every other thread in the core, but always avoids a case
+        * where virtual node associativity change causes subsequent threads
+        * of a core to be associated with different nid. However if first
+        * thread is already online, expect it to have a valid mapping.
+        */
+       if (fcpu != lcpu) {
+               WARN_ON(cpu_online(fcpu));
+               map_cpu_to_node(fcpu, nid);
+       }
+
        map_cpu_to_node(lcpu, nid);
        of_node_put(cpu);
 out: