x86/resctrl: Move monitor init work to a resctrl init call

rdt_get_mon_l3_config() is called from the arch's resctrl_arch_late_init(),
and initialises both architecture specific fields, such as hw_res->mon_scale
and resctrl filesystem fields by calling dom_data_init().

To separate the filesystem and architecture parts of resctrl, this function
needs splitting up.

Add resctrl_mon_resource_init() to do the filesystem specific work, and call
it from resctrl_init(). This runs later, but is still before the filesystem is
mounted and the rmid_ptrs[] array can be used.

  [ bp: Massage commit message. ]

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Amit Singh Tomar <amitsinght@marvell.com> # arm64
Tested-by: Shanker Donthineni <sdonthineni@nvidia.com> # arm64
Tested-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20250311183715.16445-17-james.morse@arm.com

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

@@ -586,13 +586,14 @@ void closid_free(int closid);
 int alloc_rmid(u32 closid);
 void free_rmid(u32 closid, u32 rmid);
 int rdt_get_mon_l3_config(struct rdt_resource *r);
-void __exit resctrl_mon_resource_exit(void);
+void resctrl_mon_resource_exit(void);
 bool __init rdt_cpu_has(int flag);
 void mon_event_count(void *info);
 int rdtgroup_mondata_show(struct seq_file *m, void *arg);
 void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
 		    struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
 		    cpumask_t *cpumask, int evtid, int first);
+int __init resctrl_mon_resource_init(void);
 void mbm_setup_overflow_handler(struct rdt_mon_domain *dom,
 				unsigned long delay_ms,
 				int exclude_cpu);

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

@@ -1040,7 +1040,7 @@ static int dom_data_init(struct rdt_resource *r)
 	return err;
 }
 
-static void __exit dom_data_exit(struct rdt_resource *r)
+static void dom_data_exit(struct rdt_resource *r)
 {
 	mutex_lock(&rdtgroup_mutex);
 
@@ -1176,12 +1176,40 @@ static __init int snc_get_config(void)
 	return ret;
 }
 
+/**
+ * resctrl_mon_resource_init() - Initialise global monitoring structures.
+ *
+ * Allocate and initialise global monitor resources that do not belong to a
+ * specific domain. i.e. the rmid_ptrs[] used for the limbo and free lists.
+ * Called once during boot after the struct rdt_resource's have been configured
+ * but before the filesystem is mounted.
+ * Resctrl's cpuhp callbacks may be called before this point to bring a domain
+ * online.
+ *
+ * Returns 0 for success, or -ENOMEM.
+ */
+int __init resctrl_mon_resource_init(void)
+{
+	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
+	int ret;
+
+	if (!r->mon_capable)
+		return 0;
+
+	ret = dom_data_init(r);
+	if (ret)
+		return ret;
+
+	l3_mon_evt_init(r);
+
+	return 0;
+}
+
 int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 {
 	unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
 	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
 	unsigned int threshold;
-	int ret;
 
 	snc_nodes_per_l3_cache = snc_get_config();
 
@@ -1211,10 +1239,6 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 	 */
 	resctrl_rmid_realloc_threshold = resctrl_arch_round_mon_val(threshold);
 
-	ret = dom_data_init(r);
-	if (ret)
-		return ret;
-
 	if (rdt_cpu_has(X86_FEATURE_BMEC)) {
 		u32 eax, ebx, ecx, edx;
 
@@ -1234,14 +1258,12 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 		}
 	}
 
-	l3_mon_evt_init(r);
-
 	r->mon_capable = true;
 
 	return 0;
 }
 
-void __exit resctrl_mon_resource_exit(void)
+void resctrl_mon_resource_exit(void)
 {
 	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
 

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

@@ -4102,6 +4102,19 @@ void resctrl_offline_mon_domain(struct rdt_resource *r, struct rdt_mon_domain *d
 	mutex_unlock(&rdtgroup_mutex);
 }
 
+/**
+ * domain_setup_mon_state() -  Initialise domain monitoring structures.
+ * @r:	The resource for the newly online domain.
+ * @d:	The newly online domain.
+ *
+ * Allocate monitor resources that belong to this domain.
+ * Called when the first CPU of a domain comes online, regardless of whether
+ * the filesystem is mounted.
+ * During boot this may be called before global allocations have been made by
+ * resctrl_mon_resource_init().
+ *
+ * Returns 0 for success, or -ENOMEM.
+ */
 static int domain_setup_mon_state(struct rdt_resource *r, struct rdt_mon_domain *d)
 {
 	u32 idx_limit = resctrl_arch_system_num_rmid_idx();
@@ -4252,10 +4265,16 @@ int __init resctrl_init(void)
 
 	rdtgroup_setup_default();
 
-	ret = sysfs_create_mount_point(fs_kobj, "resctrl");
+	ret = resctrl_mon_resource_init();
 	if (ret)
 		return ret;
 
+	ret = sysfs_create_mount_point(fs_kobj, "resctrl");
+	if (ret) {
+		resctrl_mon_resource_exit();
+		return ret;
+	}
+
 	ret = register_filesystem(&rdt_fs_type);
 	if (ret)
 		goto cleanup_mountpoint;
@@ -4287,6 +4306,7 @@ int __init resctrl_init(void)
 
 cleanup_mountpoint:
 	sysfs_remove_mount_point(fs_kobj, "resctrl");
+	resctrl_mon_resource_exit();
 
 	return ret;
 }