From 0d7913ac97665b1579f2e1d7ae36aa28c93dcaa1 Mon Sep 17 00:00:00 2001
From: Xie XiuQi <xiexiuqi@huawei.com>
Date: Tue, 29 Jan 2019 17:38:08 +0800
Subject: [PATCH 2804/2944] openEuler: resctrlfs: init support resctrlfs

commit e1b8071e6757590bcbc0284ff9d22768b8e41fc8 openEuler-1.0

hulk inclusion
category: feature
bugzilla: 5510
CVE: NA

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
[ Avoid X86 compile fail, change RESCTRL to RESCTRL_ARM64 ]
Signed-off-by: Xin Hao <haoxing990@gmail.com>
Reviewed-by: Baolin Wang <baolin.wang@openanolis.org>
---
 fs/Makefile               |   1 +
 fs/resctrlfs.c            | 930 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/resctrlfs.h |  97 +++++
 3 files changed, 1028 insertions(+)
 create mode 100644 fs/resctrlfs.c
 create mode 100644 include/linux/resctrlfs.h

diff --git a/fs/Makefile b/fs/Makefile
index 28354ea..6d4b42a 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -130,3 +130,4 @@ obj-y				+= exofs/ # Multiple modules
 obj-$(CONFIG_CEPH_FS)		+= ceph/
 obj-$(CONFIG_PSTORE)		+= pstore/
 obj-$(CONFIG_EFIVAR_FS)		+= efivarfs/
+obj-$(CONFIG_RESCTRL_AARCH64)		+= resctrlfs.o
diff --git a/fs/resctrlfs.c b/fs/resctrlfs.c
new file mode 100644
index 0000000..3016dea
--- /dev/null
+++ b/fs/resctrlfs.c
@@ -0,0 +1,930 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * User interface for Resource Alloction in Resource Director Technology(RDT)
+ *
+ * Copyright (C) 2016 Intel Corporation
+ *
+ * Author: Fenghua Yu <fenghua.yu@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * More information about RDT be found in the Intel (R) x86 Architecture
+ * Software Developer Manual.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/cpu.h>
+#include <linux/fs.h>
+#include <linux/sysfs.h>
+#include <linux/kernfs.h>
+#include <linux/seq_buf.h>
+#include <linux/seq_file.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/slab.h>
+#include <linux/resctrlfs.h>
+
+#include <uapi/linux/magic.h>
+
+#include <asm/resctrl.h>
+
+DEFINE_STATIC_KEY_FALSE(resctrl_enable_key);
+DEFINE_STATIC_KEY_FALSE(resctrl_mon_enable_key);
+DEFINE_STATIC_KEY_FALSE(resctrl_alloc_enable_key);
+static struct kernfs_root *resctrl_root;
+struct resctrl_group resctrl_group_default;
+LIST_HEAD(resctrl_all_groups);
+
+/* Kernel fs node for "info" directory under root */
+static struct kernfs_node *kn_info;
+
+/* Kernel fs node for "mon_groups" directory under root */
+static struct kernfs_node *kn_mongrp;
+
+/* Kernel fs node for "mon_data" directory under root */
+static struct kernfs_node *kn_mondata;
+
+/* set uid and gid of resctrl_group dirs and files to that of the creator */
+static int resctrl_group_kn_set_ugid(struct kernfs_node *kn)
+{
+	struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
+				.ia_uid = current_fsuid(),
+				.ia_gid = current_fsgid(), };
+
+	if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
+	    gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
+		return 0;
+
+	return kernfs_setattr(kn, &iattr);
+}
+
+static int resctrl_group_add_file(struct kernfs_node *parent_kn, struct rftype *rft)
+{
+	struct kernfs_node *kn;
+	int ret;
+
+	kn = __kernfs_create_file(parent_kn, rft->name, rft->mode,
+				  0, rft->kf_ops, rft, NULL, NULL);
+	if (IS_ERR(kn))
+		return PTR_ERR(kn);
+
+	ret = resctrl_group_kn_set_ugid(kn);
+	if (ret) {
+		kernfs_remove(kn);
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct rftype *res_common_files;
+static size_t res_common_files_len;
+
+int register_resctrl_specific_files(struct rftype *files, size_t len)
+{
+	if (res_common_files) {
+		pr_err("Only allowed register specific files once\n");
+		return -EINVAL;
+	}
+
+	if (!files) {
+		pr_err("Invalid input files\n");
+		return -EINVAL;
+	}
+
+	res_common_files = files;
+	res_common_files_len = len;
+
+	return 0;
+}
+
+static int __resctrl_group_add_files(struct kernfs_node *kn, unsigned long fflags,
+				     struct rftype *rfts, int len)
+{
+	struct rftype *rft;
+	int ret;
+
+	lockdep_assert_held(&resctrl_group_mutex);
+
+	for (rft = rfts; rft < rfts + len; rft++) {
+		if (rft->enable && !rft->enable(NULL))
+			continue;
+
+		if ((fflags & rft->fflags) == rft->fflags) {
+			ret = resctrl_group_add_file(kn, rft);
+			if (ret)
+				goto error;
+		}
+	}
+
+	return 0;
+error:
+	pr_warn("Failed to add %s, err=%d\n", rft->name, ret);
+	while (--rft >= rfts) {
+		if ((fflags & rft->fflags) == rft->fflags)
+			kernfs_remove_by_name(kn, rft->name);
+	}
+	return ret;
+}
+
+static int resctrl_group_add_files(struct kernfs_node *kn, unsigned long fflags)
+{
+	int ret;
+
+	if (res_common_files)
+		ret = __resctrl_group_add_files(kn, fflags, res_common_files,
+						res_common_files_len);
+
+	return ret;
+}
+
+static int resctrl_group_mkdir_info_resdir(struct resctrl_resource *r, char *name,
+				      unsigned long fflags)
+{
+	struct kernfs_node *kn_subdir;
+	int ret;
+
+	kn_subdir = kernfs_create_dir(kn_info, name,
+				      kn_info->mode, r);
+	if (IS_ERR(kn_subdir))
+		return PTR_ERR(kn_subdir);
+
+	kernfs_get(kn_subdir);
+	ret = resctrl_group_kn_set_ugid(kn_subdir);
+	if (ret)
+		return ret;
+
+	ret = resctrl_group_add_files(kn_subdir, fflags);
+	if (!ret)
+		kernfs_activate(kn_subdir);
+
+	return ret;
+}
+
+static int resctrl_group_create_info_dir(struct kernfs_node *parent_kn)
+{
+	struct resctrl_resource *r;
+	unsigned long fflags;
+	char name[32];
+	int ret;
+
+	/* create the directory */
+	kn_info = kernfs_create_dir(parent_kn, "info", parent_kn->mode, NULL);
+	if (IS_ERR(kn_info))
+		return PTR_ERR(kn_info);
+	kernfs_get(kn_info);
+
+	ret = resctrl_group_add_files(kn_info, RF_TOP_INFO);
+	if (ret)
+		goto out_destroy;
+
+	for_each_alloc_enabled_resctrl_resource(r) {
+		fflags =  r->fflags | RF_CTRL_INFO;
+		ret = resctrl_group_mkdir_info_resdir(r, r->name, fflags);
+		if (ret)
+			goto out_destroy;
+	}
+
+	for_each_mon_enabled_resctrl_resource(r) {
+		fflags =  r->fflags | RF_MON_INFO;
+		sprintf(name, "%s_MON", r->name);
+		ret = resctrl_group_mkdir_info_resdir(r, name, fflags);
+		if (ret)
+			goto out_destroy;
+	}
+
+	/*
+	 * This extra ref will be put in kernfs_remove() and guarantees
+	 * that @rdtgrp->kn is always accessible.
+	 */
+	kernfs_get(kn_info);
+
+	ret = resctrl_group_kn_set_ugid(kn_info);
+	if (ret)
+		goto out_destroy;
+
+	kernfs_activate(kn_info);
+
+	return 0;
+
+out_destroy:
+	kernfs_remove(kn_info);
+	return ret;
+}
+
+/*
+ * We don't allow resctrl_group directories to be created anywhere
+ * except the root directory. Thus when looking for the resctrl_group
+ * structure for a kernfs node we are either looking at a directory,
+ * in which case the resctrl_group structure is pointed at by the "priv"
+ * field, otherwise we have a file, and need only look to the parent
+ * to find the resctrl_group.
+ */
+static struct resctrl_group *kernfs_to_resctrl_group(struct kernfs_node *kn)
+{
+	if (kernfs_type(kn) == KERNFS_DIR) {
+		/*
+		 * All the resource directories use "kn->priv"
+		 * to point to the "struct resctrl_group" for the
+		 * resource. "info" and its subdirectories don't
+		 * have resctrl_group structures, so return NULL here.
+		 */
+		if (kn == kn_info || kn->parent == kn_info)
+			return NULL;
+		else
+			return kn->priv;
+	} else {
+		return kn->parent->priv;
+	}
+}
+
+struct resctrl_group *resctrl_group_kn_lock_live(struct kernfs_node *kn)
+{
+	struct resctrl_group *rdtgrp = kernfs_to_resctrl_group(kn);
+
+	if (!rdtgrp)
+		return NULL;
+
+	atomic_inc(&rdtgrp->waitcount);
+	kernfs_break_active_protection(kn);
+
+	mutex_lock(&resctrl_group_mutex);
+
+	/* Was this group deleted while we waited? */
+	if (rdtgrp->flags & RDT_DELETED)
+		return NULL;
+
+	return rdtgrp;
+}
+
+void resctrl_group_kn_unlock(struct kernfs_node *kn)
+{
+	struct resctrl_group *rdtgrp = kernfs_to_resctrl_group(kn);
+
+	if (!rdtgrp)
+		return;
+
+	mutex_unlock(&resctrl_group_mutex);
+
+	if (atomic_dec_and_test(&rdtgrp->waitcount) &&
+	    (rdtgrp->flags & RDT_DELETED)) {
+		kernfs_unbreak_active_protection(kn);
+		kernfs_put(rdtgrp->kn);
+		kfree(rdtgrp);
+	} else {
+		kernfs_unbreak_active_protection(kn);
+	}
+}
+
+static struct dentry *resctrl_mount(struct file_system_type *fs_type,
+				int flags, const char *unused_dev_name,
+				void *data)
+{
+	struct dentry *dentry;
+	int ret;
+
+	cpus_read_lock();
+	mutex_lock(&resctrl_group_mutex);
+	/*
+	 * resctrl file system can only be mounted once.
+	 */
+	if (static_branch_unlikely(&resctrl_enable_key)) {
+		dentry = ERR_PTR(-EBUSY);
+		goto out;
+	}
+
+	ret = parse_resctrl_group_fs_options(data);
+	if (ret) {
+		dentry = ERR_PTR(ret);
+		goto out_options;
+	}
+
+	resctrl_id_init();
+
+	ret = resctrl_group_create_info_dir(resctrl_group_default.kn);
+	if (ret) {
+		dentry = ERR_PTR(ret);
+		goto out_options;
+	}
+
+	if (resctrl_mon_capable) {
+		ret = mongroup_create_dir(resctrl_group_default.kn,
+					  NULL, "mon_groups",
+					  &kn_mongrp);
+		if (ret) {
+			dentry = ERR_PTR(ret);
+			goto out_info;
+		}
+		kernfs_get(kn_mongrp);
+
+		ret = mkdir_mondata_all(resctrl_group_default.kn,
+					&resctrl_group_default, &kn_mondata);
+		if (ret) {
+			dentry = ERR_PTR(ret);
+			goto out_mongrp;
+		}
+		kernfs_get(kn_mondata);
+		resctrl_group_default.mon.mon_data_kn = kn_mondata;
+	}
+
+	dentry = kernfs_mount(fs_type, flags, resctrl_root,
+			      RDTGROUP_SUPER_MAGIC, NULL);
+	if (IS_ERR(dentry))
+		goto out_mondata;
+
+	post_resctrl_mount();
+
+	goto out;
+
+out_mondata:
+	if (resctrl_mon_capable)
+		kernfs_remove(kn_mondata);
+out_mongrp:
+	if (resctrl_mon_capable)
+		kernfs_remove(kn_mongrp);
+out_info:
+	kernfs_remove(kn_info);
+out_options:
+	release_resctrl_group_fs_options();
+out:
+	rdt_last_cmd_clear();
+	mutex_unlock(&resctrl_group_mutex);
+	cpus_read_unlock();
+
+	return dentry;
+}
+
+static bool is_closid_match(struct task_struct *t, struct resctrl_group *r)
+{
+	return (resctrl_alloc_capable &&
+		(r->type == RDTCTRL_GROUP) && (t->closid == r->closid));
+}
+
+static bool is_rmid_match(struct task_struct *t, struct resctrl_group *r)
+{
+	return (resctrl_mon_capable &&
+		(r->type == RDTMON_GROUP) && (t->rmid == r->mon.rmid));
+}
+
+/*
+ * Move tasks from one to the other group. If @from is NULL, then all tasks
+ * in the systems are moved unconditionally (used for teardown).
+ *
+ * If @mask is not NULL the cpus on which moved tasks are running are set
+ * in that mask so the update smp function call is restricted to affected
+ * cpus.
+ */
+static void resctrl_move_group_tasks(struct resctrl_group *from, struct resctrl_group *to,
+				 struct cpumask *mask)
+{
+	struct task_struct *p, *t;
+
+	read_lock(&tasklist_lock);
+	for_each_process_thread(p, t) {
+		if (!from || is_closid_match(t, from) ||
+		    is_rmid_match(t, from)) {
+			t->closid = to->closid;
+			t->rmid = to->mon.rmid;
+
+#ifdef CONFIG_SMP
+			/*
+			 * This is safe on x86 w/o barriers as the ordering
+			 * of writing to task_cpu() and t->on_cpu is
+			 * reverse to the reading here. The detection is
+			 * inaccurate as tasks might move or schedule
+			 * before the smp function call takes place. In
+			 * such a case the function call is pointless, but
+			 * there is no other side effect.
+			 */
+			if (mask && t->on_cpu)
+				cpumask_set_cpu(task_cpu(t), mask);
+#endif
+		}
+	}
+	read_unlock(&tasklist_lock);
+}
+
+static void free_all_child_rdtgrp(struct resctrl_group *rdtgrp)
+{
+	struct resctrl_group *sentry, *stmp;
+	struct list_head *head;
+
+	head = &rdtgrp->mon.crdtgrp_list;
+	list_for_each_entry_safe(sentry, stmp, head, mon.crdtgrp_list) {
+		free_mon_id(sentry->mon.rmid);
+		list_del(&sentry->mon.crdtgrp_list);
+		kfree(sentry);
+	}
+}
+
+/*
+ * Forcibly remove all of subdirectories under root.
+ */
+static void rmdir_all_sub(void)
+{
+	struct resctrl_group *rdtgrp, *tmp;
+
+	/* Move all tasks to the default resource group */
+	resctrl_move_group_tasks(NULL, &resctrl_group_default, NULL);
+
+	list_for_each_entry_safe(rdtgrp, tmp, &resctrl_all_groups, resctrl_group_list) {
+		/* Free any child rmids */
+		free_all_child_rdtgrp(rdtgrp);
+
+		/* Remove each resctrl_group other than root */
+		if (rdtgrp == &resctrl_group_default)
+			continue;
+
+		/*
+		 * Give any CPUs back to the default group. We cannot copy
+		 * cpu_online_mask because a CPU might have executed the
+		 * offline callback already, but is still marked online.
+		 */
+		cpumask_or(&resctrl_group_default.cpu_mask,
+			   &resctrl_group_default.cpu_mask, &rdtgrp->cpu_mask);
+
+		free_mon_id(rdtgrp->mon.rmid);
+
+		kernfs_remove(rdtgrp->kn);
+		list_del(&rdtgrp->resctrl_group_list);
+		kfree(rdtgrp);
+	}
+	/* Notify online CPUs to update per cpu storage and PQR_ASSOC MSR */
+	update_closid_rmid(cpu_online_mask, &resctrl_group_default);
+
+	kernfs_remove(kn_info);
+	kernfs_remove(kn_mongrp);
+	kernfs_remove(kn_mondata);
+}
+
+static void resctrl_kill_sb(struct super_block *sb)
+{
+
+	cpus_read_lock();
+	mutex_lock(&resctrl_group_mutex);
+
+	resctrl_resource_reset();
+
+	rmdir_all_sub();
+	static_branch_disable_cpuslocked(&resctrl_alloc_enable_key);
+	static_branch_disable_cpuslocked(&resctrl_mon_enable_key);
+	static_branch_disable_cpuslocked(&resctrl_enable_key);
+	kernfs_kill_sb(sb);
+	mutex_unlock(&resctrl_group_mutex);
+	cpus_read_unlock();
+}
+
+static struct file_system_type resctrl_fs_type = {
+	.name    = "resctrl",
+	.mount   = resctrl_mount,
+	.kill_sb = resctrl_kill_sb,
+};
+
+static int mkdir_resctrl_prepare(struct kernfs_node *parent_kn,
+			     struct kernfs_node *prgrp_kn,
+			     const char *name, umode_t mode,
+			     enum rdt_group_type rtype, struct resctrl_group **r)
+{
+	struct resctrl_group *prdtgrp, *rdtgrp;
+	struct kernfs_node *kn;
+	uint files = 0;
+	int ret;
+
+	prdtgrp = resctrl_group_kn_lock_live(prgrp_kn);
+	rdt_last_cmd_clear();
+	if (!prdtgrp) {
+		ret = -ENODEV;
+		rdt_last_cmd_puts("directory was removed\n");
+		goto out_unlock;
+	}
+
+	/* allocate the resctrl_group. */
+	rdtgrp = kzalloc(sizeof(*rdtgrp), GFP_KERNEL);
+	if (!rdtgrp) {
+		ret = -ENOSPC;
+		rdt_last_cmd_puts("kernel out of memory\n");
+		goto out_unlock;
+	}
+	*r = rdtgrp;
+	rdtgrp->mon.parent = prdtgrp;
+	rdtgrp->type = rtype;
+	INIT_LIST_HEAD(&rdtgrp->mon.crdtgrp_list);
+
+	/* kernfs creates the directory for rdtgrp */
+	kn = kernfs_create_dir(parent_kn, name, mode, rdtgrp);
+	if (IS_ERR(kn)) {
+		ret = PTR_ERR(kn);
+		rdt_last_cmd_puts("kernfs create error\n");
+		goto out_free_rgrp;
+	}
+	rdtgrp->kn = kn;
+
+	/*
+	 * kernfs_remove() will drop the reference count on "kn" which
+	 * will free it. But we still need it to stick around for the
+	 * resctrl_group_kn_unlock(kn} call below. Take one extra reference
+	 * here, which will be dropped inside resctrl_group_kn_unlock().
+	 */
+	kernfs_get(kn);
+
+	ret = resctrl_group_kn_set_ugid(kn);
+	if (ret) {
+		rdt_last_cmd_puts("kernfs perm error\n");
+		goto out_destroy;
+	}
+
+	files = RFTYPE_BASE | BIT(RF_CTRLSHIFT + rtype);
+	ret = resctrl_group_add_files(kn, files);
+	if (ret) {
+		rdt_last_cmd_puts("kernfs fill error\n");
+		goto out_destroy;
+	}
+
+	if (resctrl_mon_capable) {
+		ret = alloc_mon_id();
+		if (ret < 0) {
+			rdt_last_cmd_puts("out of RMIDs\n");
+			goto out_destroy;
+		}
+		rdtgrp->mon.rmid = ret;
+
+		ret = mkdir_mondata_all(kn, rdtgrp, &rdtgrp->mon.mon_data_kn);
+		if (ret) {
+			rdt_last_cmd_puts("kernfs subdir error\n");
+			goto out_idfree;
+		}
+	}
+	kernfs_activate(kn);
+
+	/*
+	 * The caller unlocks the prgrp_kn upon success.
+	 */
+	return 0;
+
+out_idfree:
+	free_mon_id(rdtgrp->mon.rmid);
+out_destroy:
+	kernfs_remove(rdtgrp->kn);
+out_free_rgrp:
+	kfree(rdtgrp);
+out_unlock:
+	resctrl_group_kn_unlock(prgrp_kn);
+	return ret;
+}
+
+static void mkdir_resctrl_prepare_clean(struct resctrl_group *rgrp)
+{
+	kernfs_remove(rgrp->kn);
+	free_mon_id(rgrp->mon.rmid);
+	kfree(rgrp);
+}
+
+/*
+ * Create a monitor group under "mon_groups" directory of a control
+ * and monitor group(ctrl_mon). This is a resource group
+ * to monitor a subset of tasks and cpus in its parent ctrl_mon group.
+ */
+static int resctrl_group_mkdir_mon(struct kernfs_node *parent_kn,
+			      struct kernfs_node *prgrp_kn,
+			      const char *name,
+			      umode_t mode)
+{
+	struct resctrl_group *rdtgrp, *prgrp;
+	int ret;
+
+	ret = mkdir_resctrl_prepare(parent_kn, prgrp_kn, name, mode, RDTMON_GROUP,
+				&rdtgrp);
+	if (ret)
+		return ret;
+
+	prgrp = rdtgrp->mon.parent;
+	rdtgrp->closid = prgrp->closid;
+
+	/*
+	 * Add the rdtgrp to the list of rdtgrps the parent
+	 * ctrl_mon group has to track.
+	 */
+	list_add_tail(&rdtgrp->mon.crdtgrp_list, &prgrp->mon.crdtgrp_list);
+
+	resctrl_group_kn_unlock(prgrp_kn);
+	return ret;
+}
+
+/*
+ * These are resctrl_groups created under the root directory. Can be used
+ * to allocate and monitor resources.
+ */
+static int resctrl_group_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
+				   struct kernfs_node *prgrp_kn,
+				   const char *name, umode_t mode)
+{
+	struct resctrl_group *rdtgrp;
+	struct kernfs_node *kn;
+	u32 closid;
+	int ret;
+
+	ret = mkdir_resctrl_prepare(parent_kn, prgrp_kn, name, mode, RDTCTRL_GROUP,
+				&rdtgrp);
+	if (ret)
+		return ret;
+
+	kn = rdtgrp->kn;
+	ret = resctrl_id_alloc();
+	if (ret < 0) {
+		rdt_last_cmd_puts("out of CLOSIDs\n");
+		goto out_common_fail;
+	}
+	closid = ret;
+	ret = 0;
+
+	rdtgrp->closid = closid;
+	list_add(&rdtgrp->resctrl_group_list, &resctrl_all_groups);
+
+	if (resctrl_mon_capable) {
+		/*
+		 * Create an empty mon_groups directory to hold the subset
+		 * of tasks and cpus to monitor.
+		 */
+		ret = mongroup_create_dir(kn, NULL, "mon_groups", NULL);
+		if (ret) {
+			rdt_last_cmd_puts("kernfs subdir error\n");
+			goto out_id_free;
+		}
+	}
+
+	goto out_unlock;
+
+out_id_free:
+	resctrl_id_free(closid);
+	list_del(&rdtgrp->resctrl_group_list);
+out_common_fail:
+	mkdir_resctrl_prepare_clean(rdtgrp);
+out_unlock:
+	resctrl_group_kn_unlock(prgrp_kn);
+	return ret;
+}
+
+/*
+ * We allow creating mon groups only with in a directory called "mon_groups"
+ * which is present in every ctrl_mon group. Check if this is a valid
+ * "mon_groups" directory.
+ *
+ * 1. The directory should be named "mon_groups".
+ * 2. The mon group itself should "not" be named "mon_groups".
+ *   This makes sure "mon_groups" directory always has a ctrl_mon group
+ *   as parent.
+ */
+static bool is_mon_groups(struct kernfs_node *kn, const char *name)
+{
+	return (!strcmp(kn->name, "mon_groups") &&
+		strcmp(name, "mon_groups"));
+}
+
+static int resctrl_group_mkdir(struct kernfs_node *parent_kn, const char *name,
+			  umode_t mode)
+{
+	/* Do not accept '\n' to avoid unparsable situation. */
+	if (strchr(name, '\n'))
+		return -EINVAL;
+
+	/*
+	 * If the parent directory is the root directory and RDT
+	 * allocation is supported, add a control and monitoring
+	 * subdirectory
+	 */
+	if (resctrl_alloc_capable && parent_kn == resctrl_group_default.kn)
+		return resctrl_group_mkdir_ctrl_mon(parent_kn, parent_kn, name, mode);
+
+	/*
+	 * If RDT monitoring is supported and the parent directory is a valid
+	 * "mon_groups" directory, add a monitoring subdirectory.
+	 */
+	if (resctrl_mon_capable && is_mon_groups(parent_kn, name))
+		return resctrl_group_mkdir_mon(parent_kn, parent_kn->parent, name, mode);
+
+	return -EPERM;
+}
+
+static void resctrl_group_rm_mon(struct resctrl_group *rdtgrp,
+			      cpumask_var_t tmpmask)
+{
+	struct resctrl_group *prdtgrp = rdtgrp->mon.parent;
+	int cpu;
+
+	/* Give any tasks back to the parent group */
+	resctrl_move_group_tasks(rdtgrp, prdtgrp, tmpmask);
+
+	/* Update per cpu rmid of the moved CPUs first */
+	for_each_cpu(cpu, &rdtgrp->cpu_mask)
+		per_cpu(pqr_state.default_rmid, cpu) = prdtgrp->mon.rmid;
+	/*
+	 * Update the MSR on moved CPUs and CPUs which have moved
+	 * task running on them.
+	 */
+	cpumask_or(tmpmask, tmpmask, &rdtgrp->cpu_mask);
+	update_closid_rmid(tmpmask, NULL);
+
+	rdtgrp->flags = RDT_DELETED;
+	free_mon_id(rdtgrp->mon.rmid);
+
+	/*
+	 * Remove the rdtgrp from the parent ctrl_mon group's list
+	 */
+	WARN_ON(list_empty(&prdtgrp->mon.crdtgrp_list));
+	list_del(&rdtgrp->mon.crdtgrp_list);
+}
+
+static int resctrl_group_rmdir_mon(struct kernfs_node *kn, struct resctrl_group *rdtgrp,
+			      cpumask_var_t tmpmask)
+{
+	resctrl_group_rm_mon(rdtgrp, tmpmask);
+
+	/*
+	 * one extra hold on this, will drop when we kfree(rdtgrp)
+	 * in resctrl_group_kn_unlock()
+	 */
+	kernfs_get(kn);
+	kernfs_remove(rdtgrp->kn);
+
+	return 0;
+}
+
+static void resctrl_group_rm_ctrl(struct resctrl_group *rdtgrp, cpumask_var_t tmpmask)
+{
+	int cpu;
+
+	/* Give any tasks back to the default group */
+	resctrl_move_group_tasks(rdtgrp, &resctrl_group_default, tmpmask);
+
+	/* Give any CPUs back to the default group */
+	cpumask_or(&resctrl_group_default.cpu_mask,
+		   &resctrl_group_default.cpu_mask, &rdtgrp->cpu_mask);
+
+	/* Update per cpu closid and rmid of the moved CPUs first */
+	for_each_cpu(cpu, &rdtgrp->cpu_mask) {
+		per_cpu(pqr_state.default_closid, cpu) = resctrl_group_default.closid;
+		per_cpu(pqr_state.default_rmid, cpu) = resctrl_group_default.mon.rmid;
+	}
+
+	/*
+	 * Update the MSR on moved CPUs and CPUs which have moved
+	 * task running on them.
+	 */
+	cpumask_or(tmpmask, tmpmask, &rdtgrp->cpu_mask);
+	update_closid_rmid(tmpmask, NULL);
+
+	rdtgrp->flags = RDT_DELETED;
+	resctrl_id_free(rdtgrp->closid);
+	free_mon_id(rdtgrp->mon.rmid);
+
+	/*
+	 * Free all the child monitor group rmids.
+	 */
+	free_all_child_rdtgrp(rdtgrp);
+
+	list_del(&rdtgrp->resctrl_group_list);
+}
+
+static int resctrl_group_rmdir_ctrl(struct kernfs_node *kn, struct resctrl_group *rdtgrp,
+			       cpumask_var_t tmpmask)
+{
+	resctrl_group_rm_ctrl(rdtgrp, tmpmask);
+
+	/*
+	 * one extra hold on this, will drop when we kfree(rdtgrp)
+	 * in resctrl_group_kn_unlock()
+	 */
+	kernfs_get(kn);
+	kernfs_remove(rdtgrp->kn);
+
+	return 0;
+}
+
+static int resctrl_group_rmdir(struct kernfs_node *kn)
+{
+	struct kernfs_node *parent_kn = kn->parent;
+	struct resctrl_group *rdtgrp;
+	cpumask_var_t tmpmask;
+	int ret = 0;
+
+	if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL))
+		return -ENOMEM;
+
+	rdtgrp = resctrl_group_kn_lock_live(kn);
+	if (!rdtgrp) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	/*
+	 * If the resctrl_group is a ctrl_mon group and parent directory
+	 * is the root directory, remove the ctrl_mon group.
+	 *
+	 * If the resctrl_group is a mon group and parent directory
+	 * is a valid "mon_groups" directory, remove the mon group.
+	 */
+	if (rdtgrp->type == RDTCTRL_GROUP && parent_kn == resctrl_group_default.kn)
+		ret = resctrl_group_rmdir_ctrl(kn, rdtgrp, tmpmask);
+	else if (rdtgrp->type == RDTMON_GROUP &&
+		 is_mon_groups(parent_kn, kn->name))
+		ret = resctrl_group_rmdir_mon(kn, rdtgrp, tmpmask);
+	else
+		ret = -EPERM;
+
+out:
+	resctrl_group_kn_unlock(kn);
+	free_cpumask_var(tmpmask);
+	return ret;
+}
+
+static int resctrl_group_show_options(struct seq_file *seq, struct kernfs_root *kf)
+{
+	return __resctrl_group_show_options(seq);
+}
+
+static struct kernfs_syscall_ops resctrl_group_kf_syscall_ops = {
+	.mkdir		= resctrl_group_mkdir,
+	.rmdir		= resctrl_group_rmdir,
+	.show_options	= resctrl_group_show_options,
+};
+
+static void resctrl_group_default_init(struct resctrl_group *r)
+{
+	r->closid = 0;
+	r->mon.rmid = 0;
+	r->type = RDTCTRL_GROUP;
+}
+
+static int __init resctrl_group_setup_root(void)
+{
+	int ret;
+
+	resctrl_root = kernfs_create_root(&resctrl_group_kf_syscall_ops,
+				      KERNFS_ROOT_CREATE_DEACTIVATED,
+				      &resctrl_group_default);
+	if (IS_ERR(resctrl_root))
+		return PTR_ERR(resctrl_root);
+
+	mutex_lock(&resctrl_group_mutex);
+
+	resctrl_group_default_init(&resctrl_group_default);
+	INIT_LIST_HEAD(&resctrl_group_default.mon.crdtgrp_list);
+
+	list_add(&resctrl_group_default.resctrl_group_list, &resctrl_all_groups);
+
+	ret = resctrl_group_add_files(resctrl_root->kn, RF_CTRL_BASE);
+	if (ret) {
+		kernfs_destroy_root(resctrl_root);
+		goto out;
+	}
+
+	resctrl_group_default.kn = resctrl_root->kn;
+	kernfs_activate(resctrl_group_default.kn);
+
+out:
+	mutex_unlock(&resctrl_group_mutex);
+
+	return ret;
+}
+
+/*
+ * resctrl_group_init - resctrl_group initialization
+ *
+ * Setup resctrl file system including set up root, create mount point,
+ * register resctrl_group filesystem, and initialize files under root directory.
+ *
+ * Return: 0 on success or -errno
+ */
+int __init resctrl_group_init(void)
+{
+	int ret = 0;
+
+	ret = resctrl_group_setup_root();
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_mount_point(fs_kobj, "resctrl");
+	if (ret)
+		goto cleanup_root;
+
+	ret = register_filesystem(&resctrl_fs_type);
+	if (ret)
+		goto cleanup_mountpoint;
+
+	return 0;
+
+cleanup_mountpoint:
+	sysfs_remove_mount_point(fs_kobj, "resctrl");
+cleanup_root:
+	kernfs_destroy_root(resctrl_root);
+
+	return ret;
+}
diff --git a/include/linux/resctrlfs.h b/include/linux/resctrlfs.h
new file mode 100644
index 0000000..4eeac66
--- /dev/null
+++ b/include/linux/resctrlfs.h
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RESCTRLFS_H
+#define _RESCTRLFS_H
+
+#include <linux/sched.h>
+#include <linux/kernfs.h>
+#include <linux/jump_label.h>
+
+#include <linux/seq_buf.h>
+#include <linux/seq_file.h>
+
+struct resctrl_resource {
+	int			rid;
+	bool			alloc_enabled;
+	bool			mon_enabled;
+	bool			alloc_capable;
+	bool			mon_capable;
+	char			*name;
+	struct list_head	domains;
+	struct list_head	evt_list;
+	unsigned long		fflags;
+
+	void *res;
+};
+
+DECLARE_STATIC_KEY_FALSE(resctrl_enable_key);
+
+/* rftype.flags */
+#define RFTYPE_FLAGS_CPUS_LIST	1
+
+/*
+ * Define the file type flags for base and info directories.
+ */
+#define RFTYPE_INFO			BIT(0)
+#define RFTYPE_BASE			BIT(1)
+#define RF_CTRLSHIFT			4
+#define RF_MONSHIFT			5
+#define RF_TOPSHIFT			6
+#define RFTYPE_CTRL			BIT(RF_CTRLSHIFT)
+#define RFTYPE_MON			BIT(RF_MONSHIFT)
+#define RFTYPE_TOP			BIT(RF_TOPSHIFT)
+#define RFTYPE_RES_SMMU			BIT(7)
+#define RFTYPE_RES_CACHE		BIT(8)
+#define RFTYPE_RES_MB			BIT(9)
+#define RFTYPE_RES_MC			BIT(10)
+#define RF_CTRL_INFO			(RFTYPE_INFO | RFTYPE_CTRL)
+#define RF_MON_INFO			(RFTYPE_INFO | RFTYPE_MON)
+#define RF_TOP_INFO			(RFTYPE_INFO | RFTYPE_TOP)
+#define RF_CTRL_BASE			(RFTYPE_BASE | RFTYPE_CTRL)
+
+/* List of all resource groups */
+extern struct list_head resctrl_all_groups;
+
+/**
+ * struct rftype - describe each file in the resctrl file system
+ * @name:	File name
+ * @mode:	Access mode
+ * @kf_ops:	File operations
+ * @flags:	File specific RFTYPE_FLAGS_* flags
+ * @fflags:	File specific RF_* or RFTYPE_* flags
+ * @seq_show:	Show content of the file
+ * @write:	Write to the file
+ */
+struct rftype {
+	char			*name;
+	umode_t			mode;
+	struct kernfs_ops	*kf_ops;
+	unsigned long		flags;
+	unsigned long		fflags;
+
+	bool (*enable)(void *arg);
+
+	int (*seq_show)(struct kernfs_open_file *of,
+			struct seq_file *sf, void *v);
+	/*
+	 * write() is the generic write callback which maps directly to
+	 * kernfs write operation and overrides all other operations.
+	 * Maximum write size is determined by ->max_write_len.
+	 */
+	ssize_t (*write)(struct kernfs_open_file *of,
+			 char *buf, size_t nbytes, loff_t off);
+};
+
+DECLARE_STATIC_KEY_FALSE(resctrl_alloc_enable_key);
+extern struct rdtgroup resctrl_group_default;
+
+int __init resctrl_group_init(void);
+
+int register_resctrl_specific_files(struct rftype *files, size_t len);
+extern struct kernfs_ops resctrl_group_kf_single_ops;
+
+extern struct rdtgroup *resctrl_group_kn_lock_live(struct kernfs_node *kn);
+void resctrl_group_kn_unlock(struct kernfs_node *kn);
+
+void post_resctrl_mount(void);
+
+#endif
-- 
1.8.3.1

