Re: [PATCH 05/11] fs/resctrl: Use accurate type for rdt_resource::rid

["Luck, Tony" <tony.luck@intel.com>]

On Mon, Mar 02, 2026 at 10:46:11AM -0800, Reinette Chatre wrote:

> -	/* Must be the last */
> -	RDT_NUM_RESOURCES,
> +	/* Additions to enum need to update RDT_NUM_RESOURCES. */
>  };
>  
> +#define RDT_NUM_RESOURCES (RDT_RESOURCE_PERF_PKG + 1)

Alternative approach that doesn't rely on developers reading
that comment and updating the define.

Replace the RDT_NUM_RESOURCES #define with a variable initialized
to ARRAY_SIZE(rdt_resources_all).

-Tony

From b31a874c7199347d875fd6e9505d41aa2639eafd Mon Sep 17 00:00:00 2001
From: Reinette Chatre <reinette.chatre@intel.com>
Date: Mon, 2 Mar 2026 10:46:11 -0800
Subject: [PATCH] fs/resctrl: Use accurate type for rdt_resource::rid

Every resctrl resource has a unique ID described by enum resctrl_res_level.
enum resctrl_res_level is used in all resource ID initializations and all
resource ID comparisons. All functions consuming the resource ID expects an
enum resctrl_res_level. Of the four structures that contain a resource ID
(struct mon_data, struct mon_evt, struct rdt_domain_hdr, and struct
 rdt_resource) only struct rdt_resource does not use enum resctrl_res_level.

Switch the type of rdt_resource::rid to be enum resctrl_res_level to make
it obvious what values are valid, match the type everywhere this member is
used, and obtain benefits from tools that can flag any enum misuse.

Use a variable rdt_num_resources to replace the define of RDT_NUM_RESOURCES
in the enum to enable tools to catch when a switch() on the resource ID does
not handle all the resources and thus help flag which switch statements need
an update when a new resource is added.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
 include/linux/resctrl.h            | 11 +++++------
 arch/x86/kernel/cpu/resctrl/core.c |  9 ++++++---
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 006e57fd7ca5..ef2efa2e4b39 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -27,13 +27,15 @@ int proc_resctrl_show(struct seq_file *m,
 
 #endif
 
+extern int rdt_num_resources;
+
 /* max value for struct rdt_domain's mbps_val */
 #define MBA_MAX_MBPS   U32_MAX
 
 /* Walk all possible resources, with variants for only controls or monitors. */
 #define for_each_rdt_resource(_r)						\
 	for ((_r) = resctrl_arch_get_resource(0);				\
-	     (_r) && (_r)->rid < RDT_NUM_RESOURCES;				\
+	     (_r) && (_r)->rid < rdt_num_resources;				\
 	     (_r) = resctrl_arch_get_resource((_r)->rid + 1))
 
 #define for_each_capable_rdt_resource(r)				      \
@@ -54,9 +56,6 @@ enum resctrl_res_level {
 	RDT_RESOURCE_MBA,
 	RDT_RESOURCE_SMBA,
 	RDT_RESOURCE_PERF_PKG,
-
-	/* Must be the last */
-	RDT_NUM_RESOURCES,
 };
 
 /**
@@ -319,7 +318,7 @@ struct resctrl_mon {
  * @cdp_capable:	Is the CDP feature available on this resource
  */
 struct rdt_resource {
-	int			rid;
+	enum resctrl_res_level	rid;
 	bool			alloc_capable;
 	bool			mon_capable;
 	enum resctrl_scope	ctrl_scope;
@@ -336,7 +335,7 @@ struct rdt_resource {
 
 /*
  * Get the resource that exists at this level. If the level is not supported
- * a dummy/not-capable resource can be returned. Levels >= RDT_NUM_RESOURCES
+ * a dummy/not-capable resource can be returned. Levels >= rdt_num_resources
  * will return NULL.
  */
 struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l);
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index db787c4dee61..2557bb639555 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -16,6 +16,7 @@
 
 #define pr_fmt(fmt)	"resctrl: " fmt
 
+#include <linux/array_size.h>
 #include <linux/cpu.h>
 #include <linux/slab.h>
 #include <linux/err.h>
@@ -57,7 +58,7 @@ static void mba_wrmsr_amd(struct msr_param *m);
 #define ctrl_domain_init(id) LIST_HEAD_INIT(rdt_resources_all[id].r_resctrl.ctrl_domains)
 #define mon_domain_init(id) LIST_HEAD_INIT(rdt_resources_all[id].r_resctrl.mon_domains)
 
-struct rdt_hw_resource rdt_resources_all[RDT_NUM_RESOURCES] = {
+struct rdt_hw_resource rdt_resources_all[] = {
 	[RDT_RESOURCE_L3] =
 	{
 		.r_resctrl = {
@@ -110,6 +111,8 @@ struct rdt_hw_resource rdt_resources_all[RDT_NUM_RESOURCES] = {
 	},
 };
 
+int rdt_num_resources = ARRAY_SIZE(rdt_resources_all);
+
 /**
  * resctrl_arch_system_num_rmid_idx - Compute number of supported RMIDs
  *				      (minimum across all mon_capable resource)
@@ -131,7 +134,7 @@ u32 resctrl_arch_system_num_rmid_idx(void)
 
 struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
 {
-	if (l >= RDT_NUM_RESOURCES)
+	if (l >= rdt_num_resources)
 		return NULL;
 
 	return &rdt_resources_all[l].r_resctrl;
@@ -1121,7 +1124,7 @@ static int __init resctrl_arch_late_init(void)
 	int state, ret, i;
 
 	/* for_each_rdt_resource() requires all rid to be initialised. */
-	for (i = 0; i < RDT_NUM_RESOURCES; i++)
+	for (i = 0; i < rdt_num_resources; i++)
 		rdt_resources_all[i].r_resctrl.rid = i;
 
 	/*
-- 
2.53.0