Subject: [PATCH 2/3] powerpc/cacheinfo: Remove the redundant get_shared_cpu_map()

From: Parth Shah <[email-masked]>
Date: Tue, 15 Jun 2021 12:38:03 +0530

From: "Gautham R. Shenoy" <[email-masked]>

The helper function get_shared_cpu_map() was added in

'commit 500fe5f550ec ("powerpc/cacheinfo: Report the correct
shared_cpu_map on big-cores")'

and subsequently expanded upon in

'commit 0be47634db0b ("powerpc/cacheinfo: Print correct cache-sibling
map/list for L2 cache")'

in order to help report the correct groups of threads sharing these caches
on big-core systems where groups of threads within a core can share
different sets of caches.

Now that powerpc/cacheinfo is aware of "ibm,thread-groups" property,
cache->shared_cpu_map contains the correct set of thread-siblings
sharing the cache. Hence we no longer need the functions
get_shared_cpu_map(). This patch removes this function. We also remove
the helper function index_dir_to_cpu() which was only called by
get_shared_cpu_map().

With these functions removed, we can still see the correct
cache-sibling map/list for L1 and L2 caches on systems with L1 and L2
caches distributed among groups of threads in a core.

With this patch, on a SMT8 POWER10 system where the L1 and L2 caches
are split between the two groups of threads in a core, for CPUs 8,9,
the L1-Data, L1-Instruction, L2, L3 cache CPU sibling list is as
follows:

$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8,10,12,14
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8,10,12,14
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8,10,12,14
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8-15
/sys/devices/system/cpu/cpu9/cache/index0/shared_cpu_list:9,11,13,15
/sys/devices/system/cpu/cpu9/cache/index1/shared_cpu_list:9,11,13,15
/sys/devices/system/cpu/cpu9/cache/index2/shared_cpu_list:9,11,13,15
/sys/devices/system/cpu/cpu9/cache/index3/shared_cpu_list:8-15

$ ppc64_cpu --smt=4
$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8,10
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8,10
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8,10
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8-11
/sys/devices/system/cpu/cpu9/cache/index0/shared_cpu_list:9,11
/sys/devices/system/cpu/cpu9/cache/index1/shared_cpu_list:9,11
/sys/devices/system/cpu/cpu9/cache/index2/shared_cpu_list:9,11
/sys/devices/system/cpu/cpu9/cache/index3/shared_cpu_list:8-11

$ ppc64_cpu --smt=2
$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8-9
/sys/devices/system/cpu/cpu9/cache/index0/shared_cpu_list:9
/sys/devices/system/cpu/cpu9/cache/index1/shared_cpu_list:9
/sys/devices/system/cpu/cpu9/cache/index2/shared_cpu_list:9
/sys/devices/system/cpu/cpu9/cache/index3/shared_cpu_list:8-9

$ ppc64_cpu --smt=1
$ grep . /sys/devices/system/cpu/cpu[89]/cache/index[0123]/shared_cpu_list
/sys/devices/system/cpu/cpu8/cache/index0/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index1/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index2/shared_cpu_list:8
/sys/devices/system/cpu/cpu8/cache/index3/shared_cpu_list:8

Signed-off-by: Gautham R. Shenoy <[email-masked]>
---
 arch/powerpc/kernel/cacheinfo.c | 41 +--------------------------------
 1 file changed, 1 insertion(+), 40 deletions(-)

diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c
index 5a6925d87424..20d91693eac1 100644
--- a/arch/powerpc/kernel/cacheinfo.c
+++ b/arch/powerpc/kernel/cacheinfo.c
@@ -675,45 +675,6 @@ static ssize_t level_show(struct kobject *k, struct kobj_attribute *attr, char *
 static struct kobj_attribute cache_level_attr =
 	__ATTR(level, 0444, level_show, NULL);
 
-static unsigned int index_dir_to_cpu(struct cache_index_dir *index)
-{
-	struct kobject *index_dir_kobj = &index->kobj;
-	struct kobject *cache_dir_kobj = index_dir_kobj->parent;
-	struct kobject *cpu_dev_kobj = cache_dir_kobj->parent;
-	struct device *dev = kobj_to_dev(cpu_dev_kobj);
-
-	return dev->id;
-}
-
-/*
- * On big-core systems, each core has two groups of CPUs each of which
- * has its own L1-cache. The thread-siblings which share l1-cache with
- * @cpu can be obtained via cpu_smallcore_mask().
- *
- * On some big-core systems, the L2 cache is shared only between some
- * groups of siblings. This is already parsed and encoded in
- * cpu_l2_cache_mask().
- *
- * TODO: cache_lookup_or_instantiate() needs to be made aware of the
- *       "ibm,thread-groups" property so that cache->shared_cpu_map
- *       reflects the correct siblings on platforms that have this
- *       device-tree property. This helper function is only a stop-gap
- *       solution so that we report the correct siblings to the
- *       userspace via sysfs.
- */
-static const struct cpumask *get_shared_cpu_map(struct cache_index_dir *index, struct cache *cache)
-{
-	if (has_big_cores) {
-		int cpu = index_dir_to_cpu(index);
-		if (cache->level == 1)
-			return cpu_smallcore_mask(cpu);
-		if (cache->level == 2 && thread_group_shares_l2)
-			return cpu_l2_cache_mask(cpu);
-	}
-
-	return &cache->shared_cpu_map;
-}
-
 static ssize_t
 show_shared_cpumap(struct kobject *k, struct kobj_attribute *attr, char *buf, bool list)
 {
@@ -724,7 +685,7 @@ show_shared_cpumap(struct kobject *k, struct kobj_attribute *attr, char *buf, bo
 	index = kobj_to_cache_index_dir(k);
 	cache = index->cache;
 
-	mask = get_shared_cpu_map(index, cache);
+	mask = &cache->shared_cpu_map;
 
 	return cpumap_print_to_pagebuf(list, buf, mask);
 }
-- 
2.26.3