[PATCH v2 05/10] powerpc/smp: Dont assume l2-cache to be superset of sibling

Srikar Dronamraju
2020-07-21T11:39:13Z

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-kernel@vger.kernel.org>
Cc: Michael Ellerman <michaele@au1.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Nick Piggin <npiggin@au1.ibm.com>
Cc: Oliver OHalloran <oliveroh@au1.ibm.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Michael Neuling <mikey@linux.ibm.com>
Cc: Anton Blanchard <anton@au1.ibm.com>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Vaidyanathan Srinivasan <svaidy@linux.ibm.com>
Cc: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
Changelog v1 -> v2:
powerpc/smp: Dont assume l2-cache to be superset of sibling
Set cpumask after verifying l2-cache. (Gautham)

arch/powerpc/kernel/smp.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 72f16dc0cb26..57468877499a 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1196,6 +1196,7 @@ static bool update_mask_by_l2(int cpu, struct cpumask *(*mask_fn)(int))
if (!l2_cache)
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
@@ -1278,29 +1279,30 @@ 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