Fix to make it work where CPUs dont have a l2-cache element.
------------>8-----------------------------------------8<---------------------
>From b25d47b01b7195b1df19083a4043fa6a87a901a3 Mon Sep 17 00:00:00 2001
From: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
Date: Thu, 9 Jul 2020 13:33:38 +0530
Subject: [PATCH v5.2 05/10] 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.
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: LKML <linux-ker...@vger.kernel.org>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Anton Blanchard <an...@ozlabs.org>
Cc: Oliver O'Halloran <ooh...@gmail.com>
Cc: Nathan Lynch <nath...@linux.ibm.com>
Cc: Michael Neuling <mi...@neuling.org>
Cc: Gautham R Shenoy <e...@linux.vnet.ibm.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Valentin Schneider <valentin.schnei...@arm.com>
Cc: Jordan Niethe <jniet...@gmail.com>
Cc: Vaidyanathan Srinivasan <sva...@linux.ibm.com>
Reviewed-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com>
Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
---
Changelog v1 -> v2:
Set cpumask after verifying l2-cache. (Gautham)
Changelog v5 -> v5.2:
If cpu has no l2-cache set cpumask as per its
sibling mask. (Michael Ellerman)
arch/powerpc/kernel/smp.c | 43 +++++++++++++++++++++++++++++--------------
1 file changed, 29 insertions(+), 14 deletions(-)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 9f4333d..168532e 100644
--- 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)
--
2.17.1
