arm_mpam: resctrl: Add boilerplate cpuhp and domain allocation

resctrl has its own data structures to describe its resources. We can't use
these directly as we play tricks with the 'MBA' resource, picking the MPAM
controls or monitors that best apply. We may export the same component as
both L3 and MBA.

Add mpam_resctrl_res[] as the array of class->resctrl mappings we are
exporting, and add the cpuhp hooks that allocated and free the resctrl
domain structures. Only the mpam control feature are considered here and
monitor support will be added later.

While we're here, plumb in a few other obvious things.

CONFIG_ARM_CPU_RESCTRL is used to allow this code to be built even though
it can't yet be linked against resctrl.

Tested-by: Gavin Shan <gshan@redhat.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Zeng Heng <zengheng4@huawei.com>
Tested-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com>
Tested-by: Jesse Chick <jessechick@os.amperecomputing.com>
Reviewed-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Co-developed-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>

drivers/resctrl/mpam_resctrl.c

@@ -0,0 +1,324 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2025 Arm Ltd.
+
+#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__
+
+#include <linux/arm_mpam.h>
+#include <linux/cacheinfo.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/printk.h>
+#include <linux/rculist.h>
+#include <linux/resctrl.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/mpam.h>
+
+#include "mpam_internal.h"
+
+/*
+ * The classes we've picked to map to resctrl resources, wrapped
+ * in with their resctrl structure.
+ * Class pointer may be NULL.
+ */
+static struct mpam_resctrl_res mpam_resctrl_controls[RDT_NUM_RESOURCES];
+
+#define for_each_mpam_resctrl_control(res, rid)					\
+	for (rid = 0, res = &mpam_resctrl_controls[rid];			\
+	     rid < RDT_NUM_RESOURCES;						\
+	     rid++, res = &mpam_resctrl_controls[rid])
+
+/* The lock for modifying resctrl's domain lists from cpuhp callbacks. */
+static DEFINE_MUTEX(domain_list_lock);
+
+bool resctrl_arch_alloc_capable(void)
+{
+	struct mpam_resctrl_res *res;
+	enum resctrl_res_level rid;
+
+	for_each_mpam_resctrl_control(res, rid) {
+		if (res->resctrl_res.alloc_capable)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * MSC may raise an error interrupt if it sees an out or range partid/pmg,
+ * and go on to truncate the value. Regardless of what the hardware supports,
+ * only the system wide safe value is safe to use.
+ */
+u32 resctrl_arch_get_num_closid(struct rdt_resource *ignored)
+{
+	return mpam_partid_max + 1;
+}
+
+struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
+{
+	if (l >= RDT_NUM_RESOURCES)
+		return NULL;
+
+	return &mpam_resctrl_controls[l].resctrl_res;
+}
+
+static int mpam_resctrl_control_init(struct mpam_resctrl_res *res)
+{
+	/* TODO: initialise the resctrl resources */
+
+	return 0;
+}
+
+static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
+{
+	struct mpam_class *class = comp->class;
+
+	if (class->type == MPAM_CLASS_CACHE)
+		return comp->comp_id;
+
+	/* TODO: repaint domain ids to match the L3 domain ids */
+	/* Otherwise, expose the ID used by the firmware table code. */
+	return comp->comp_id;
+}
+
+static void mpam_resctrl_domain_hdr_init(int cpu, struct mpam_component *comp,
+					 enum resctrl_res_level rid,
+					 struct rdt_domain_hdr *hdr)
+{
+	lockdep_assert_cpus_held();
+
+	INIT_LIST_HEAD(&hdr->list);
+	hdr->id = mpam_resctrl_pick_domain_id(cpu, comp);
+	hdr->rid = rid;
+	cpumask_set_cpu(cpu, &hdr->cpu_mask);
+}
+
+static void mpam_resctrl_online_domain_hdr(unsigned int cpu,
+					   struct rdt_domain_hdr *hdr)
+{
+	lockdep_assert_cpus_held();
+
+	cpumask_set_cpu(cpu, &hdr->cpu_mask);
+}
+
+/**
+ * mpam_resctrl_offline_domain_hdr() - Update the domain header to remove a CPU.
+ * @cpu:	The CPU to remove from the domain.
+ * @hdr:	The domain's header.
+ *
+ * Removes @cpu from the header mask. If this was the last CPU in the domain,
+ * the domain header is removed from its parent list and true is returned,
+ * indicating the parent structure can be freed.
+ * If there are other CPUs in the domain, returns false.
+ */
+static bool mpam_resctrl_offline_domain_hdr(unsigned int cpu,
+					    struct rdt_domain_hdr *hdr)
+{
+	lockdep_assert_held(&domain_list_lock);
+
+	cpumask_clear_cpu(cpu, &hdr->cpu_mask);
+	if (cpumask_empty(&hdr->cpu_mask)) {
+		list_del_rcu(&hdr->list);
+		synchronize_rcu();
+		return true;
+	}
+
+	return false;
+}
+
+static void mpam_resctrl_domain_insert(struct list_head *list,
+				       struct rdt_domain_hdr *new)
+{
+	struct rdt_domain_hdr *err;
+	struct list_head *pos = NULL;
+
+	lockdep_assert_held(&domain_list_lock);
+
+	err = resctrl_find_domain(list, new->id, &pos);
+	if (WARN_ON_ONCE(err))
+		return;
+
+	list_add_tail_rcu(&new->list, pos);
+}
+
+static struct mpam_resctrl_dom *
+mpam_resctrl_alloc_domain(unsigned int cpu, struct mpam_resctrl_res *res)
+{
+	int err;
+	struct mpam_resctrl_dom *dom;
+	struct rdt_ctrl_domain *ctrl_d;
+	struct mpam_class *class = res->class;
+	struct mpam_component *comp_iter, *ctrl_comp;
+	struct rdt_resource *r = &res->resctrl_res;
+
+	lockdep_assert_held(&domain_list_lock);
+
+	ctrl_comp = NULL;
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(comp_iter, &class->components, class_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (cpumask_test_cpu(cpu, &comp_iter->affinity)) {
+			ctrl_comp = comp_iter;
+			break;
+		}
+	}
+
+	/* class has no component for this CPU */
+	if (WARN_ON_ONCE(!ctrl_comp))
+		return ERR_PTR(-EINVAL);
+
+	dom = kzalloc_node(sizeof(*dom), GFP_KERNEL, cpu_to_node(cpu));
+	if (!dom)
+		return ERR_PTR(-ENOMEM);
+
+	if (r->alloc_capable) {
+		dom->ctrl_comp = ctrl_comp;
+
+		ctrl_d = &dom->resctrl_ctrl_dom;
+		mpam_resctrl_domain_hdr_init(cpu, ctrl_comp, r->rid, &ctrl_d->hdr);
+		ctrl_d->hdr.type = RESCTRL_CTRL_DOMAIN;
+		err = resctrl_online_ctrl_domain(r, ctrl_d);
+		if (err)
+			goto free_domain;
+
+		mpam_resctrl_domain_insert(&r->ctrl_domains, &ctrl_d->hdr);
+	} else {
+		pr_debug("Skipped control domain online - no controls\n");
+	}
+	return dom;
+
+free_domain:
+	kfree(dom);
+	dom = ERR_PTR(err);
+
+	return dom;
+}
+
+static struct mpam_resctrl_dom *
+mpam_resctrl_get_domain_from_cpu(int cpu, struct mpam_resctrl_res *res)
+{
+	struct mpam_resctrl_dom *dom;
+	struct rdt_resource *r = &res->resctrl_res;
+
+	lockdep_assert_cpus_held();
+
+	list_for_each_entry_rcu(dom, &r->ctrl_domains, resctrl_ctrl_dom.hdr.list) {
+		if (cpumask_test_cpu(cpu, &dom->ctrl_comp->affinity))
+			return dom;
+	}
+
+	return NULL;
+}
+
+int mpam_resctrl_online_cpu(unsigned int cpu)
+{
+	struct mpam_resctrl_res *res;
+	enum resctrl_res_level rid;
+
+	guard(mutex)(&domain_list_lock);
+	for_each_mpam_resctrl_control(res, rid) {
+		struct mpam_resctrl_dom *dom;
+		struct rdt_resource *r = &res->resctrl_res;
+
+		if (!res->class)
+			continue;	// dummy_resource;
+
+		dom = mpam_resctrl_get_domain_from_cpu(cpu, res);
+		if (!dom) {
+			dom = mpam_resctrl_alloc_domain(cpu, res);
+			if (IS_ERR(dom))
+				return PTR_ERR(dom);
+		} else {
+			if (r->alloc_capable) {
+				struct rdt_ctrl_domain *ctrl_d = &dom->resctrl_ctrl_dom;
+
+				mpam_resctrl_online_domain_hdr(cpu, &ctrl_d->hdr);
+			}
+		}
+	}
+
+	resctrl_online_cpu(cpu);
+
+	return 0;
+}
+
+void mpam_resctrl_offline_cpu(unsigned int cpu)
+{
+	struct mpam_resctrl_res *res;
+	enum resctrl_res_level rid;
+
+	resctrl_offline_cpu(cpu);
+
+	guard(mutex)(&domain_list_lock);
+	for_each_mpam_resctrl_control(res, rid) {
+		struct mpam_resctrl_dom *dom;
+		struct rdt_ctrl_domain *ctrl_d;
+		bool ctrl_dom_empty;
+		struct rdt_resource *r = &res->resctrl_res;
+
+		if (!res->class)
+			continue;	// dummy resource
+
+		dom = mpam_resctrl_get_domain_from_cpu(cpu, res);
+		if (WARN_ON_ONCE(!dom))
+			continue;
+
+		if (r->alloc_capable) {
+			ctrl_d = &dom->resctrl_ctrl_dom;
+			ctrl_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr);
+			if (ctrl_dom_empty)
+				resctrl_offline_ctrl_domain(&res->resctrl_res, ctrl_d);
+		} else {
+			ctrl_dom_empty = true;
+		}
+
+		if (ctrl_dom_empty)
+			kfree(dom);
+	}
+}
+
+int mpam_resctrl_setup(void)
+{
+	int err = 0;
+	struct mpam_resctrl_res *res;
+	enum resctrl_res_level rid;
+
+	cpus_read_lock();
+	for_each_mpam_resctrl_control(res, rid) {
+		INIT_LIST_HEAD_RCU(&res->resctrl_res.ctrl_domains);
+		res->resctrl_res.rid = rid;
+	}
+
+	/* TODO: pick MPAM classes to map to resctrl resources */
+
+	/* Initialise the resctrl structures from the classes */
+	for_each_mpam_resctrl_control(res, rid) {
+		if (!res->class)
+			continue;	// dummy resource
+
+		err = mpam_resctrl_control_init(res);
+		if (err) {
+			pr_debug("Failed to initialise rid %u\n", rid);
+			break;
+		}
+	}
+	cpus_read_unlock();
+
+	if (err) {
+		pr_debug("Internal error %d - resctrl not supported\n", err);
+		return err;
+	}
+
+	if (!resctrl_arch_alloc_capable()) {
+		pr_debug("No alloc(%u) found - resctrl not supported\n",
+			 resctrl_arch_alloc_capable());
+		return -EOPNOTSUPP;
+	}
+
+	/* TODO: call resctrl_init() */
+
+	return 0;
+}