powerpc/cacheinfo: Lookup cache by dt node and thread-group id

Currently the cacheinfo code on powerpc indexes the "cache" objects
(modelling the L1/L2/L3 caches) where the key is device-tree node
corresponding to that cache. On some of the POWER server platforms
thread-groups within the core share different sets of caches (Eg: On
SMT8 POWER9 systems, threads 0,2,4,6 of a core share L1 cache and
threads 1,3,5,7 of the same core share another L1 cache). On such
platforms, there is a single device-tree node corresponding to that
cache and the cache-configuration within the threads of the core is
indicated via "ibm,thread-groups" device-tree property.

Since the current code is not aware of the "ibm,thread-groups"
property, on the aforementoined systems, cacheinfo code still treats
all the threads in the core to be sharing the cache because of the
single device-tree node (In the earlier example, the cacheinfo code
would says CPUs 0-7 share L1 cache).

In this patch, we make the powerpc cacheinfo code aware of the
"ibm,thread-groups" property. We indexe the "cache" objects by the
key-pair (device-tree node, thread-group id). For any CPUX, for a
given level of cache, the thread-group id is defined to be the first
CPU in the "ibm,thread-groups" cache-group containing CPUX. For levels
of cache which are not represented in "ibm,thread-groups" property,
the thread-group id is -1.

[parth: Remove "static" keyword for the definition of "thread_group_l1_cache_map"
and "thread_group_l2_cache_map" to get rid of the compile error.]

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Parth Shah <parth@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210728175607.591679-2-parth@linux.ibm.com

diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index 03b3d010cbab667a48eef50c535859b468db5fae..1259040cc3a4adf3c2b8c568a1320f0f34524b9e 100644 (file)
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -33,6 +33,9 @@ extern bool coregroup_enabled;
 extern int cpu_to_chip_id(int cpu);
 extern int *chip_id_lookup_table;
 
+DECLARE_PER_CPU(cpumask_var_t, thread_group_l1_cache_map);
+DECLARE_PER_CPU(cpumask_var_t, thread_group_l2_cache_map);
+
 #ifdef CONFIG_SMP
 
 struct smp_ops_t {

diff --git a/arch/powerpc/kernel/cacheinfo.c b/arch/powerpc/kernel/cacheinfo.c
index 6f903e9aa20ba1c74cbae117c7fa6df8d3d88532..5a6925d87424d91d68499bfba2454d7b16c8f6db 100644 (file)
--- a/arch/powerpc/kernel/cacheinfo.c
+++ b/arch/powerpc/kernel/cacheinfo.c
@@ -120,6 +120,7 @@ struct cache {
        struct cpumask shared_cpu_map; /* online CPUs using this cache */
        int type;                      /* split cache disambiguation */
        int level;                     /* level not explicit in device tree */
+       int group_id;                  /* id of the group of threads that share this cache */
        struct list_head list;         /* global list of cache objects */
        struct cache *next_local;      /* next cache of >= level */
 };
@@ -142,22 +143,24 @@ static const char *cache_type_string(const struct cache *cache)
 }
 
 static void cache_init(struct cache *cache, int type, int level,
-                      struct device_node *ofnode)
+                      struct device_node *ofnode, int group_id)
 {
        cache->type = type;
        cache->level = level;
        cache->ofnode = of_node_get(ofnode);
+       cache->group_id = group_id;
        INIT_LIST_HEAD(&cache->list);
        list_add(&cache->list, &cache_list);
 }
 
-static struct cache *new_cache(int type, int level, struct device_node *ofnode)
+static struct cache *new_cache(int type, int level,
+                              struct device_node *ofnode, int group_id)
 {
        struct cache *cache;
 
        cache = kzalloc(sizeof(*cache), GFP_KERNEL);
        if (cache)
-               cache_init(cache, type, level, ofnode);
+               cache_init(cache, type, level, ofnode, group_id);
 
        return cache;
 }
@@ -309,20 +312,24 @@ static struct cache *cache_find_first_sibling(struct cache *cache)
                return cache;
 
        list_for_each_entry(iter, &cache_list, list)
-               if (iter->ofnode == cache->ofnode && iter->next_local == cache)
+               if (iter->ofnode == cache->ofnode &&
+                   iter->group_id == cache->group_id &&
+                   iter->next_local == cache)
                        return iter;
 
        return cache;
 }
 
-/* return the first cache on a local list matching node */
-static struct cache *cache_lookup_by_node(const struct device_node *node)
+/* return the first cache on a local list matching node and thread-group id */
+static struct cache *cache_lookup_by_node_group(const struct device_node *node,
+                                               int group_id)
 {
        struct cache *cache = NULL;
        struct cache *iter;
 
        list_for_each_entry(iter, &cache_list, list) {
-               if (iter->ofnode != node)
+               if (iter->ofnode != node ||
+                   iter->group_id != group_id)
                        continue;
                cache = cache_find_first_sibling(iter);
                break;
@@ -352,14 +359,15 @@ static int cache_is_unified_d(const struct device_node *np)
                CACHE_TYPE_UNIFIED_D : CACHE_TYPE_UNIFIED;
 }
 
-static struct cache *cache_do_one_devnode_unified(struct device_node *node, int level)
+static struct cache *cache_do_one_devnode_unified(struct device_node *node, int group_id,
+                                                 int level)
 {
        pr_debug("creating L%d ucache for %pOFP\n", level, node);
 
-       return new_cache(cache_is_unified_d(node), level, node);
+       return new_cache(cache_is_unified_d(node), level, node, group_id);
 }
 
-static struct cache *cache_do_one_devnode_split(struct device_node *node,
+static struct cache *cache_do_one_devnode_split(struct device_node *node, int group_id,
                                                int level)
 {
        struct cache *dcache, *icache;
@@ -367,8 +375,8 @@ static struct cache *cache_do_one_devnode_split(struct device_node *node,
        pr_debug("creating L%d dcache and icache for %pOFP\n", level,
                 node);
 
-       dcache = new_cache(CACHE_TYPE_DATA, level, node);
-       icache = new_cache(CACHE_TYPE_INSTRUCTION, level, node);
+       dcache = new_cache(CACHE_TYPE_DATA, level, node, group_id);
+       icache = new_cache(CACHE_TYPE_INSTRUCTION, level, node, group_id);
 
        if (!dcache || !icache)
                goto err;
@@ -382,31 +390,32 @@ err:
        return NULL;
 }
 
-static struct cache *cache_do_one_devnode(struct device_node *node, int level)
+static struct cache *cache_do_one_devnode(struct device_node *node, int group_id, int level)
 {
        struct cache *cache;
 
        if (cache_node_is_unified(node))
-               cache = cache_do_one_devnode_unified(node, level);
+               cache = cache_do_one_devnode_unified(node, group_id, level);
        else
-               cache = cache_do_one_devnode_split(node, level);
+               cache = cache_do_one_devnode_split(node, group_id, level);
 
        return cache;
 }
 
 static struct cache *cache_lookup_or_instantiate(struct device_node *node,
+                                                int group_id,
                                                 int level)
 {
        struct cache *cache;
 
-       cache = cache_lookup_by_node(node);
+       cache = cache_lookup_by_node_group(node, group_id);
 
        WARN_ONCE(cache && cache->level != level,
                  "cache level mismatch on lookup (got %d, expected %d)\n",
                  cache->level, level);
 
        if (!cache)
-               cache = cache_do_one_devnode(node, level);
+               cache = cache_do_one_devnode(node, group_id, level);
 
        return cache;
 }
@@ -443,7 +452,27 @@ static void do_subsidiary_caches_debugcheck(struct cache *cache)
                  of_node_get_device_type(cache->ofnode));
 }
 
-static void do_subsidiary_caches(struct cache *cache)
+/*
+ * If sub-groups of threads in a core containing @cpu_id share the
+ * L@level-cache (information obtained via "ibm,thread-groups"
+ * device-tree property), then we identify the group by the first
+ * thread-sibling in the group. We define this to be the group-id.
+ *
+ * In the absence of any thread-group information for L@level-cache,
+ * this function returns -1.
+ */
+static int get_group_id(unsigned int cpu_id, int level)
+{
+       if (has_big_cores && level == 1)
+               return cpumask_first(per_cpu(thread_group_l1_cache_map,
+                                            cpu_id));
+       else if (thread_group_shares_l2 && level == 2)
+               return cpumask_first(per_cpu(thread_group_l2_cache_map,
+                                            cpu_id));
+       return -1;
+}
+
+static void do_subsidiary_caches(struct cache *cache, unsigned int cpu_id)
 {
        struct device_node *subcache_node;
        int level = cache->level;
@@ -452,9 +481,11 @@ static void do_subsidiary_caches(struct cache *cache)
 
        while ((subcache_node = of_find_next_cache_node(cache->ofnode))) {
                struct cache *subcache;
+               int group_id;
 
                level++;
-               subcache = cache_lookup_or_instantiate(subcache_node, level);
+               group_id = get_group_id(cpu_id, level);
+               subcache = cache_lookup_or_instantiate(subcache_node, group_id, level);
                of_node_put(subcache_node);
                if (!subcache)
                        break;
@@ -468,6 +499,7 @@ static struct cache *cache_chain_instantiate(unsigned int cpu_id)
 {
        struct device_node *cpu_node;
        struct cache *cpu_cache = NULL;
+       int group_id;
 
        pr_debug("creating cache object(s) for CPU %i\n", cpu_id);
 
@@ -476,11 +508,13 @@ static struct cache *cache_chain_instantiate(unsigned int cpu_id)
        if (!cpu_node)
                goto out;
 
-       cpu_cache = cache_lookup_or_instantiate(cpu_node, 1);
+       group_id = get_group_id(cpu_id, 1);
+
+       cpu_cache = cache_lookup_or_instantiate(cpu_node, group_id, 1);
        if (!cpu_cache)
                goto out;
 
-       do_subsidiary_caches(cpu_cache);
+       do_subsidiary_caches(cpu_cache, cpu_id);
 
        cache_cpu_set(cpu_cache, cpu_id);
 out:
@@ -848,13 +882,15 @@ static struct cache *cache_lookup_by_cpu(unsigned int cpu_id)
 {
        struct device_node *cpu_node;
        struct cache *cache;
+       int group_id;
 
        cpu_node = of_get_cpu_node(cpu_id, NULL);
        WARN_ONCE(!cpu_node, "no OF node found for CPU %i\n", cpu_id);
        if (!cpu_node)
                return NULL;
 
-       cache = cache_lookup_by_node(cpu_node);
+       group_id = get_group_id(cpu_id, 1);
+       cache = cache_lookup_by_node_group(cpu_node, group_id);
        of_node_put(cpu_node);
 
        return cache;

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 447b78a87c8f2adcb5f46c0073b7cdbea84ec275..a7fcac44a8e29b8801f70862566c5f276ea02640 100644 (file)
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -122,14 +122,14 @@ static struct thread_groups_list tgl[NR_CPUS] __initdata;
  * On big-cores system, thread_group_l1_cache_map for each CPU corresponds to
  * the set its siblings that share the L1-cache.
  */
-static DEFINE_PER_CPU(cpumask_var_t, thread_group_l1_cache_map);
+DEFINE_PER_CPU(cpumask_var_t, thread_group_l1_cache_map);
 
 /*
  * On some big-cores system, thread_group_l2_cache_map for each CPU
  * corresponds to the set its siblings within the core that share the
  * L2-cache.
  */
-static DEFINE_PER_CPU(cpumask_var_t, thread_group_l2_cache_map);
+DEFINE_PER_CPU(cpumask_var_t, thread_group_l2_cache_map);
 
 /* SMP operations for this machine */
 struct smp_ops_t *smp_ops;