Resctrl code open codes a search for information about a given cache
level in a couple of places (and more are on the way).

Provide a new inline function get_cpu_cacheinfo_level() in
<linux/cacheinfo.h> to do the search and return a pointer to
the cacheinfo structure.

Simplify the existing get_cpu_cacheinfo_id() by using this new
function to do the search.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
 include/linux/cacheinfo.h | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index 2cb15fe4fe12..b4d99052d186 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -113,10 +113,11 @@ int acpi_get_cache_info(unsigned int cpu,
 const struct attribute_group *cache_get_priv_group(struct cacheinfo *this_leaf);
 
 /*
- * Get the id of the cache associated with @cpu at level @level.
+ * Get the cacheinfo structure for the cache associated with @cpu at
+ * level @level.
  * cpuhp lock must be held.
  */
-static inline int get_cpu_cacheinfo_id(int cpu, int level)
+static inline struct cacheinfo *get_cpu_cacheinfo_level(int cpu, int level)
 {
 	struct cpu_cacheinfo *ci = get_cpu_cacheinfo(cpu);
 	int i;
@@ -124,12 +125,23 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)
 	for (i = 0; i < ci->num_leaves; i++) {
 		if (ci->info_list[i].level == level) {
 			if (ci->info_list[i].attributes & CACHE_ID)
-				return ci->info_list[i].id;
-			return -1;
+				return &ci->info_list[i];
+			return NULL;
 		}
 	}
 
-	return -1;
+	return NULL;
+}
+
+/*
+ * Get the id of the cache associated with @cpu at level @level.
+ * cpuhp lock must be held.
+ */
+static inline int get_cpu_cacheinfo_id(int cpu, int level)
+{
+	struct cacheinfo *ci = get_cpu_cacheinfo_level(cpu, level);
+
+	return ci ? ci->id : -1;
 }
 
 #ifdef CONFIG_ARM64
-- 
2.45.0

On Wed, Jun 05, 2024 at 09:14:25AM -0700, Tony Luck wrote:
>  /*
> - * Get the id of the cache associated with @cpu at level @level.
> + * Get the cacheinfo structure for the cache associated with @cpu at
> + * level @level.
>   * cpuhp lock must be held.
>   */
> -static inline int get_cpu_cacheinfo_id(int cpu, int level)
> +static inline struct cacheinfo *get_cpu_cacheinfo_level(int cpu, int level)
>  {
>  	struct cpu_cacheinfo *ci = get_cpu_cacheinfo(cpu);
>  	int i;
> @@ -124,12 +125,23 @@ static inline int get_cpu_cacheinfo_id(int cpu, int level)

So:

	lockdep_assert_cpus_held()

?

>  	for (i = 0; i < ci->num_leaves; i++) {
>  		if (ci->info_list[i].level == level) {
>  			if (ci->info_list[i].attributes & CACHE_ID)
> -				return ci->info_list[i].id;
> -			return -1;
> +				return &ci->info_list[i];
> +			return NULL;
>  		}
>  	}
>  
> -	return -1;
> +	return NULL;
> +}

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette