x86/resctrl: Add a separate schema list for resctrl

Resctrl exposes schemata to user-space, which allow the control values
to be specified for a group of tasks.

User-visible properties of the interface, (such as the schemata names
and how the values are parsed) are rooted in a struct provided by the
architecture code. (struct rdt_hw_resource). Once a second architecture
uses resctrl, this would allow user-visible properties to diverge
between architectures.

These properties should come from the resctrl code that will be common
to all architectures. Resctrl has no per-schema structure, only struct
rdt_{hw_,}resource. Create a struct resctrl_schema to hold the
rdt_resource. Before a second architecture can be supported, this
structure will also need to hold the schema name visible to user-space
and the type of configuration values for resctrl.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jamie Iles <jamie@nuviainc.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lkml.kernel.org/r/20210728170637.25610-4-james.morse@arm.com

arch/x86/kernel/cpu/resctrl/internal.h

@@ -110,6 +110,7 @@ extern unsigned int resctrl_cqm_threshold;
 extern bool rdt_alloc_capable;
 extern bool rdt_mon_capable;
 extern unsigned int rdt_mon_features;
+extern struct list_head resctrl_schema_all;
 
 enum rdt_group_type {
 	RDTCTRL_GROUP = 0,

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -39,6 +39,9 @@ static struct kernfs_root *rdt_root;
 struct rdtgroup rdtgroup_default;
 LIST_HEAD(rdt_all_groups);
 
+/* list of entries for the schemata file */
+LIST_HEAD(resctrl_schema_all);
+
 /* Kernel fs node for "info" directory under root */
 static struct kernfs_node *kn_info;
 
@@ -2109,6 +2112,35 @@ static int rdt_enable_ctx(struct rdt_fs_context *ctx)
 	return ret;
 }
 
+static int schemata_list_create(void)
+{
+	struct resctrl_schema *s;
+	struct rdt_resource *r;
+
+	for_each_alloc_enabled_rdt_resource(r) {
+		s = kzalloc(sizeof(*s), GFP_KERNEL);
+		if (!s)
+			return -ENOMEM;
+
+		s->res = r;
+
+		INIT_LIST_HEAD(&s->list);
+		list_add(&s->list, &resctrl_schema_all);
+	}
+
+	return 0;
+}
+
+static void schemata_list_destroy(void)
+{
+	struct resctrl_schema *s, *tmp;
+
+	list_for_each_entry_safe(s, tmp, &resctrl_schema_all, list) {
+		list_del(&s->list);
+		kfree(s);
+	}
+}
+
 static int rdt_get_tree(struct fs_context *fc)
 {
 	struct rdt_fs_context *ctx = rdt_fc2context(fc);
@@ -2130,11 +2162,17 @@ static int rdt_get_tree(struct fs_context *fc)
 	if (ret < 0)
 		goto out_cdp;
 
+	ret = schemata_list_create();
+	if (ret) {
+		schemata_list_destroy();
+		goto out_mba;
+	}
+
 	closid_init();
 
 	ret = rdtgroup_create_info_dir(rdtgroup_default.kn);
 	if (ret < 0)
-		goto out_mba;
+		goto out_schemata_free;
 
 	if (rdt_mon_capable) {
 		ret = mongroup_create_dir(rdtgroup_default.kn,
@@ -2184,6 +2222,8 @@ static int rdt_get_tree(struct fs_context *fc)
 		kernfs_remove(kn_mongrp);
 out_info:
 	kernfs_remove(kn_info);
+out_schemata_free:
+	schemata_list_destroy();
 out_mba:
 	if (ctx->enable_mba_mbps)
 		set_mba_sc(false);
@@ -2425,6 +2465,7 @@ static void rdt_kill_sb(struct super_block *sb)
 	rmdir_all_sub();
 	rdt_pseudo_lock_release();
 	rdtgroup_default.mode = RDT_MODE_SHAREABLE;
+	schemata_list_destroy();
 	static_branch_disable_cpuslocked(&rdt_alloc_enable_key);
 	static_branch_disable_cpuslocked(&rdt_mon_enable_key);
 	static_branch_disable_cpuslocked(&rdt_enable_key);

include/linux/resctrl.h

@@ -153,4 +153,15 @@ struct rdt_resource {
 
 };
 
+/**
+ * struct resctrl_schema - configuration abilities of a resource presented to
+ *			   user-space
+ * @list:	Member of resctrl_schema_all.
+ * @res:	The resource structure exported by the architecture to describe
+ *		the hardware that is configured by this schema.
+ */
+struct resctrl_schema {
+	struct list_head		list;
+	struct rdt_resource		*res;
+};
 #endif /* _RESCTRL_H */