powerpc/smp: Dont assume l2-cache to be superset of sibling

Current code assumes that cpumask of cpus sharing a l2-cache mask will
always be a superset of cpu_sibling_mask.

Lets stop that assumption. cpu_l2_cache_mask is a superset of
cpu_sibling_mask if and only if shared_caches is set.

Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200913171038.GB11808@linux.vnet.ibm.com

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 9f4333d..168532e 100644 (file)
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1186,9 +1186,23 @@ static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int))
        int i;
 
        l2_cache = cpu_to_l2cache(cpu);
-       if (!l2_cache)
+       if (!l2_cache) {
+               struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
+
+               /*
+                * If no l2cache for this CPU, assume all siblings to share
+                * cache with this CPU.
+                */
+               if (has_big_cores)
+                       sibling_mask = cpu_smallcore_mask;
+
+               for_each_cpu(i, sibling_mask(cpu))
+                       set_cpus_related(cpu, i, cpu_l2_cache_mask);
+
                return false;
+       }
 
+       cpumask_set_cpu(cpu, mask_fn(cpu));
        for_each_cpu(i, cpu_online_mask) {
                /*
                 * when updating the marks the current CPU has not been marked
@@ -1271,29 +1285,30 @@ static void add_cpu_to_masks(int cpu)
         * add it to it's own thread sibling mask.
         */
        cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
+       cpumask_set_cpu(cpu, cpu_core_mask(cpu));
 
        for (i = first_thread; i < first_thread + threads_per_core; i++)
                if (cpu_online(i))
                        set_cpus_related(i, cpu, cpu_sibling_mask);
 
        add_cpu_to_smallcore_masks(cpu);
-       /*
-        * Copy the thread sibling mask into the cache sibling mask
-        * and mark any CPUs that share an L2 with this CPU.
-        */
-       for_each_cpu(i, cpu_sibling_mask(cpu))
-               set_cpus_related(cpu, i, cpu_l2_cache_mask);
        update_mask_by_l2(cpu, cpu_l2_cache_mask);
 
-       /*
-        * Copy the cache sibling mask into core sibling mask and mark
-        * any CPUs on the same chip as this CPU.
-        */
-       for_each_cpu(i, cpu_l2_cache_mask(cpu))
-               set_cpus_related(cpu, i, cpu_core_mask);
+       if (pkg_id == -1) {
+               struct cpumask *(*mask)(int) = cpu_sibling_mask;
+
+               /*
+                * Copy the sibling mask into core sibling mask and
+                * mark any CPUs on the same chip as this CPU.
+                */
+               if (shared_caches)
+                       mask = cpu_l2_cache_mask;
+
+               for_each_cpu(i, mask(cpu))
+                       set_cpus_related(cpu, i, cpu_core_mask);
 
-       if (pkg_id == -1)
                return;
+       }
 
        for_each_cpu(i, cpu_online_mask)
                if (get_physical_package_id(i) == pkg_id)