ARK-OS/arkos/kernel/fs/resctrl/pseudo_lock.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Resource Director Technology (RDT)
 *
 * Pseudo-locking support built on top of Cache Allocation Technology (CAT)
 *
 * Copyright (C) 2018 Intel Corporation
 *
 * Author: Reinette Chatre <reinette.chatre@intel.com>
 */

#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt

#include <linux/cacheinfo.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/debugfs.h>
#include <linux/kthread.h>
#include <linux/mman.h>
#include <linux/pm_qos.h>
#include <linux/resctrl.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

#include "internal.h"

/*
 * Major number assigned to and shared by all devices exposing
 * pseudo-locked regions.
 */
static unsigned int pseudo_lock_major;

static unsigned long pseudo_lock_minor_avail = GENMASK(MINORBITS, 0);

static char *pseudo_lock_devnode(const struct device *dev, umode_t *mode)
{
	const struct rdtgroup *rdtgrp;

	rdtgrp = dev_get_drvdata(dev);
	if (mode)
		*mode = 0600;
	guard(mutex)(&rdtgroup_mutex);
	return kasprintf(GFP_KERNEL, "pseudo_lock/%s", rdt_kn_name(rdtgrp->kn));
}

static const struct class pseudo_lock_class = {
	.name = "pseudo_lock",
	.devnode = pseudo_lock_devnode,
};

/**
 * pseudo_lock_minor_get - Obtain available minor number
 * @minor: Pointer to where new minor number will be stored
 *
 * A bitmask is used to track available minor numbers. Here the next free
 * minor number is marked as unavailable and returned.
 *
 * Return: 0 on success, <0 on failure.
 */
static int pseudo_lock_minor_get(unsigned int *minor)
{
	unsigned long first_bit;

	first_bit = find_first_bit(&pseudo_lock_minor_avail, MINORBITS);

	if (first_bit == MINORBITS)
		return -ENOSPC;

	__clear_bit(first_bit, &pseudo_lock_minor_avail);
	*minor = first_bit;

	return 0;
}

/**
 * pseudo_lock_minor_release - Return minor number to available
 * @minor: The minor number made available
 */
static void pseudo_lock_minor_release(unsigned int minor)
{
	__set_bit(minor, &pseudo_lock_minor_avail);
}

/**
 * region_find_by_minor - Locate a pseudo-lock region by inode minor number
 * @minor: The minor number of the device representing pseudo-locked region
 *
 * When the character device is accessed we need to determine which
 * pseudo-locked region it belongs to. This is done by matching the minor
 * number of the device to the pseudo-locked region it belongs.
 *
 * Minor numbers are assigned at the time a pseudo-locked region is associated
 * with a cache instance.
 *
 * Return: On success return pointer to resource group owning the pseudo-locked
 *         region, NULL on failure.
 */
static struct rdtgroup *region_find_by_minor(unsigned int minor)
{
	struct rdtgroup *rdtgrp, *rdtgrp_match = NULL;

	list_for_each_entry(rdtgrp, &rdt_all_groups, rdtgroup_list) {
		if (rdtgrp->plr && rdtgrp->plr->minor == minor) {
			rdtgrp_match = rdtgrp;
			break;
		}
	}
	return rdtgrp_match;
}

/**
 * struct pseudo_lock_pm_req - A power management QoS request list entry
 * @list:	Entry within the @pm_reqs list for a pseudo-locked region
 * @req:	PM QoS request
 */
struct pseudo_lock_pm_req {
	struct list_head list;
	struct dev_pm_qos_request req;
};

static void pseudo_lock_cstates_relax(struct pseudo_lock_region *plr)
{
	struct pseudo_lock_pm_req *pm_req, *next;

	list_for_each_entry_safe(pm_req, next, &plr->pm_reqs, list) {
		dev_pm_qos_remove_request(&pm_req->req);
		list_del(&pm_req->list);
		kfree(pm_req);
	}
}

/**
 * pseudo_lock_cstates_constrain - Restrict cores from entering C6
 * @plr: Pseudo-locked region
 *
 * To prevent the cache from being affected by power management entering
 * C6 has to be avoided. This is accomplished by requesting a latency
 * requirement lower than lowest C6 exit latency of all supported
 * platforms as found in the cpuidle state tables in the intel_idle driver.
 * At this time it is possible to do so with a single latency requirement
 * for all supported platforms.
 *
 * Since Goldmont is supported, which is affected by X86_BUG_MONITOR,
 * the ACPI latencies need to be considered while keeping in mind that C2
 * may be set to map to deeper sleep states. In this case the latency
 * requirement needs to prevent entering C2 also.
 *
 * Return: 0 on success, <0 on failure
 */
static int pseudo_lock_cstates_constrain(struct pseudo_lock_region *plr)
{
	struct pseudo_lock_pm_req *pm_req;
	int cpu;
	int ret;

	for_each_cpu(cpu, &plr->d->hdr.cpu_mask) {
		pm_req = kzalloc_obj(*pm_req);
		if (!pm_req) {
			rdt_last_cmd_puts("Failure to allocate memory for PM QoS\n");
			ret = -ENOMEM;
			goto out_err;
		}
		ret = dev_pm_qos_add_request(get_cpu_device(cpu),
					     &pm_req->req,
					     DEV_PM_QOS_RESUME_LATENCY,
					     30);
		if (ret < 0) {
			rdt_last_cmd_printf("Failed to add latency req CPU%d\n",
					    cpu);
			kfree(pm_req);
			ret = -1;
			goto out_err;
		}
		list_add(&pm_req->list, &plr->pm_reqs);
	}

	return 0;

out_err:
	pseudo_lock_cstates_relax(plr);
	return ret;
}

/**
 * pseudo_lock_region_clear - Reset pseudo-lock region data
 * @plr: pseudo-lock region
 *
 * All content of the pseudo-locked region is reset - any memory allocated
 * freed.
 *
 * Return: void
 */
static void pseudo_lock_region_clear(struct pseudo_lock_region *plr)
{
	plr->size = 0;
	plr->line_size = 0;
	kfree(plr->kmem);
	plr->kmem = NULL;
	plr->s = NULL;
	if (plr->d)
		plr->d->plr = NULL;
	plr->d = NULL;
	plr->cbm = 0;
	plr->debugfs_dir = NULL;
}

/**
 * pseudo_lock_region_init - Initialize pseudo-lock region information
 * @plr: pseudo-lock region
 *
 * Called after user provided a schemata to be pseudo-locked. From the
 * schemata the &struct pseudo_lock_region is on entry already initialized
 * with the resource, domain, and capacity bitmask. Here the information
 * required for pseudo-locking is deduced from this data and &struct
 * pseudo_lock_region initialized further. This information includes:
 * - size in bytes of the region to be pseudo-locked
 * - cache line size to know the stride with which data needs to be accessed
 *   to be pseudo-locked
 * - a cpu associated with the cache instance on which the pseudo-locking
 *   flow can be executed
 *
 * Return: 0 on success, <0 on failure. Descriptive error will be written
 * to last_cmd_status buffer.
 */
static int pseudo_lock_region_init(struct pseudo_lock_region *plr)
{
	enum resctrl_scope scope = plr->s->res->ctrl_scope;
	struct cacheinfo *ci;
	int ret;

	if (WARN_ON_ONCE(scope != RESCTRL_L2_CACHE && scope != RESCTRL_L3_CACHE))
		return -ENODEV;

	/* Pick the first cpu we find that is associated with the cache. */
	plr->cpu = cpumask_first(&plr->d->hdr.cpu_mask);

	if (!cpu_online(plr->cpu)) {
		rdt_last_cmd_printf("CPU %u associated with cache not online\n",
				    plr->cpu);
		ret = -ENODEV;
		goto out_region;
	}

	ci = get_cpu_cacheinfo_level(plr->cpu, scope);
	if (ci) {
		plr->line_size = ci->coherency_line_size;
		plr->size = rdtgroup_cbm_to_size(plr->s->res, plr->d, plr->cbm);
		return 0;
	}

	ret = -1;
	rdt_last_cmd_puts("Unable to determine cache line size\n");
out_region:
	pseudo_lock_region_clear(plr);
	return ret;
}

/**
 * pseudo_lock_init - Initialize a pseudo-lock region
 * @rdtgrp: resource group to which new pseudo-locked region will belong
 *
 * A pseudo-locked region is associated with a resource group. When this
 * association is created the pseudo-locked region is initialized. The
 * details of the pseudo-locked region are not known at this time so only
 * allocation is done and association established.
 *
 * Return: 0 on success, <0 on failure
 */
static int pseudo_lock_init(struct rdtgroup *rdtgrp)
{
	struct pseudo_lock_region *plr;

	plr = kzalloc_obj(*plr);
	if (!plr)
		return -ENOMEM;

	init_waitqueue_head(&plr->lock_thread_wq);
	INIT_LIST_HEAD(&plr->pm_reqs);
	rdtgrp->plr = plr;
	return 0;
}

/**
 * pseudo_lock_region_alloc - Allocate kernel memory that will be pseudo-locked
 * @plr: pseudo-lock region
 *
 * Initialize the details required to set up the pseudo-locked region and
 * allocate the contiguous memory that will be pseudo-locked to the cache.
 *
 * Return: 0 on success, <0 on failure.  Descriptive error will be written
 * to last_cmd_status buffer.
 */
static int pseudo_lock_region_alloc(struct pseudo_lock_region *plr)
{
	int ret;

	ret = pseudo_lock_region_init(plr);
	if (ret < 0)
		return ret;

	/*
	 * We do not yet support contiguous regions larger than
	 * KMALLOC_MAX_SIZE.
	 */
	if (plr->size > KMALLOC_MAX_SIZE) {
		rdt_last_cmd_puts("Requested region exceeds maximum size\n");
		ret = -E2BIG;
		goto out_region;
	}

	plr->kmem = kzalloc(plr->size, GFP_KERNEL);
	if (!plr->kmem) {
		rdt_last_cmd_puts("Unable to allocate memory\n");
		ret = -ENOMEM;
		goto out_region;
	}

	ret = 0;
	goto out;
out_region:
	pseudo_lock_region_clear(plr);
out:
	return ret;
}

/**
 * pseudo_lock_free - Free a pseudo-locked region
 * @rdtgrp: resource group to which pseudo-locked region belonged
 *
 * The pseudo-locked region's resources have already been released, or not
 * yet created at this point. Now it can be freed and disassociated from the
 * resource group.
 *
 * Return: void
 */
static void pseudo_lock_free(struct rdtgroup *rdtgrp)
{
	pseudo_lock_region_clear(rdtgrp->plr);
	kfree(rdtgrp->plr);
	rdtgrp->plr = NULL;
}

/**
 * rdtgroup_monitor_in_progress - Test if monitoring in progress
 * @rdtgrp: resource group being queried
 *
 * Return: 1 if monitor groups have been created for this resource
 * group, 0 otherwise.
 */
static int rdtgroup_monitor_in_progress(struct rdtgroup *rdtgrp)
{
	return !list_empty(&rdtgrp->mon.crdtgrp_list);
}

/**
 * rdtgroup_locksetup_user_restrict - Restrict user access to group
 * @rdtgrp: resource group needing access restricted
 *
 * A resource group used for cache pseudo-locking cannot have cpus or tasks
 * assigned to it. This is communicated to the user by restricting access
 * to all the files that can be used to make such changes.
 *
 * Permissions restored with rdtgroup_locksetup_user_restore()
 *
 * Return: 0 on success, <0 on failure. If a failure occurs during the
 * restriction of access an attempt will be made to restore permissions but
 * the state of the mode of these files will be uncertain when a failure
 * occurs.
 */
static int rdtgroup_locksetup_user_restrict(struct rdtgroup *rdtgrp)
{
	int ret;

	ret = rdtgroup_kn_mode_restrict(rdtgrp, "tasks");
	if (ret)
		return ret;

	ret = rdtgroup_kn_mode_restrict(rdtgrp, "cpus");
	if (ret)
		goto err_tasks;

	ret = rdtgroup_kn_mode_restrict(rdtgrp, "cpus_list");
	if (ret)
		goto err_cpus;

	if (resctrl_arch_mon_capable()) {
		ret = rdtgroup_kn_mode_restrict(rdtgrp, "mon_groups");
		if (ret)
			goto err_cpus_list;
	}

	ret = 0;
	goto out;

err_cpus_list:
	rdtgroup_kn_mode_restore(rdtgrp, "cpus_list", 0777);
err_cpus:
	rdtgroup_kn_mode_restore(rdtgrp, "cpus", 0777);
err_tasks:
	rdtgroup_kn_mode_restore(rdtgrp, "tasks", 0777);
out:
	return ret;
}

/**
 * rdtgroup_locksetup_user_restore - Restore user access to group
 * @rdtgrp: resource group needing access restored
 *
 * Restore all file access previously removed using
 * rdtgroup_locksetup_user_restrict()
 *
 * Return: 0 on success, <0 on failure.  If a failure occurs during the
 * restoration of access an attempt will be made to restrict permissions
 * again but the state of the mode of these files will be uncertain when
 * a failure occurs.
 */
static int rdtgroup_locksetup_user_restore(struct rdtgroup *rdtgrp)
{
	int ret;

	ret = rdtgroup_kn_mode_restore(rdtgrp, "tasks", 0777);
	if (ret)
		return ret;

	ret = rdtgroup_kn_mode_restore(rdtgrp, "cpus", 0777);
	if (ret)
		goto err_tasks;

	ret = rdtgroup_kn_mode_restore(rdtgrp, "cpus_list", 0777);
	if (ret)
		goto err_cpus;

	if (resctrl_arch_mon_capable()) {
		ret = rdtgroup_kn_mode_restore(rdtgrp, "mon_groups", 0777);
		if (ret)
			goto err_cpus_list;
	}

	ret = 0;
	goto out;

err_cpus_list:
	rdtgroup_kn_mode_restrict(rdtgrp, "cpus_list");
err_cpus:
	rdtgroup_kn_mode_restrict(rdtgrp, "cpus");
err_tasks:
	rdtgroup_kn_mode_restrict(rdtgrp, "tasks");
out:
	return ret;
}

/**
 * rdtgroup_locksetup_enter - Resource group enters locksetup mode
 * @rdtgrp: resource group requested to enter locksetup mode
 *
 * A resource group enters locksetup mode to reflect that it would be used
 * to represent a pseudo-locked region and is in the process of being set
 * up to do so. A resource group used for a pseudo-locked region would
 * lose the closid associated with it so we cannot allow it to have any
 * tasks or cpus assigned nor permit tasks or cpus to be assigned in the
 * future. Monitoring of a pseudo-locked region is not allowed either.
 *
 * The above and more restrictions on a pseudo-locked region are checked
 * for and enforced before the resource group enters the locksetup mode.
 *
 * Returns: 0 if the resource group successfully entered locksetup mode, <0
 * on failure. On failure the last_cmd_status buffer is updated with text to
 * communicate details of failure to the user.
 */
int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp)
{
	int ret;

	/*
	 * The default resource group can neither be removed nor lose the
	 * default closid associated with it.
	 */
	if (rdtgrp == &rdtgroup_default) {
		rdt_last_cmd_puts("Cannot pseudo-lock default group\n");
		return -EINVAL;
	}

	/*
	 * Cache Pseudo-locking not supported when CDP is enabled.
	 *
	 * Some things to consider if you would like to enable this
	 * support (using L3 CDP as example):
	 * - When CDP is enabled two separate resources are exposed,
	 *   L3DATA and L3CODE, but they are actually on the same cache.
	 *   The implication for pseudo-locking is that if a
	 *   pseudo-locked region is created on a domain of one
	 *   resource (eg. L3CODE), then a pseudo-locked region cannot
	 *   be created on that same domain of the other resource
	 *   (eg. L3DATA). This is because the creation of a
	 *   pseudo-locked region involves a call to wbinvd that will
	 *   affect all cache allocations on particular domain.
	 * - Considering the previous, it may be possible to only
	 *   expose one of the CDP resources to pseudo-locking and
	 *   hide the other. For example, we could consider to only
	 *   expose L3DATA and since the L3 cache is unified it is
	 *   still possible to place instructions there are execute it.
	 * - If only one region is exposed to pseudo-locking we should
	 *   still keep in mind that availability of a portion of cache
	 *   for pseudo-locking should take into account both resources.
	 *   Similarly, if a pseudo-locked region is created in one
	 *   resource, the portion of cache used by it should be made
	 *   unavailable to all future allocations from both resources.
	 */
	if (resctrl_arch_get_cdp_enabled(RDT_RESOURCE_L3) ||
	    resctrl_arch_get_cdp_enabled(RDT_RESOURCE_L2)) {
		rdt_last_cmd_puts("CDP enabled\n");
		return -EINVAL;
	}

	/*
	 * Not knowing the bits to disable prefetching implies that this
	 * platform does not support Cache Pseudo-Locking.
	 */
	if (resctrl_arch_get_prefetch_disable_bits() == 0) {
		rdt_last_cmd_puts("Pseudo-locking not supported\n");
		return -EINVAL;
	}

	if (rdtgroup_monitor_in_progress(rdtgrp)) {
		rdt_last_cmd_puts("Monitoring in progress\n");
		return -EINVAL;
	}

	if (rdtgroup_tasks_assigned(rdtgrp)) {
		rdt_last_cmd_puts("Tasks assigned to resource group\n");
		return -EINVAL;
	}

	if (!cpumask_empty(&rdtgrp->cpu_mask)) {
		rdt_last_cmd_puts("CPUs assigned to resource group\n");
		return -EINVAL;
	}

	if (rdtgroup_locksetup_user_restrict(rdtgrp)) {
		rdt_last_cmd_puts("Unable to modify resctrl permissions\n");
		return -EIO;
	}

	ret = pseudo_lock_init(rdtgrp);
	if (ret) {
		rdt_last_cmd_puts("Unable to init pseudo-lock region\n");
		goto out_release;
	}

	/*
	 * If this system is capable of monitoring a rmid would have been
	 * allocated when the control group was created. This is not needed
	 * anymore when this group would be used for pseudo-locking. This
	 * is safe to call on platforms not capable of monitoring.
	 */
	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);

	ret = 0;
	goto out;

out_release:
	rdtgroup_locksetup_user_restore(rdtgrp);
out:
	return ret;
}

/**
 * rdtgroup_locksetup_exit - resource group exist locksetup mode
 * @rdtgrp: resource group
 *
 * When a resource group exits locksetup mode the earlier restrictions are
 * lifted.
 *
 * Return: 0 on success, <0 on failure
 */
int rdtgroup_locksetup_exit(struct rdtgroup *rdtgrp)
{
	int ret;

	if (resctrl_arch_mon_capable()) {
		ret = alloc_rmid(rdtgrp->closid);
		if (ret < 0) {
			rdt_last_cmd_puts("Out of RMIDs\n");
			return ret;
		}
		rdtgrp->mon.rmid = ret;
	}

	ret = rdtgroup_locksetup_user_restore(rdtgrp);
	if (ret) {
		free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
		return ret;
	}

	pseudo_lock_free(rdtgrp);
	return 0;
}

/**
 * rdtgroup_cbm_overlaps_pseudo_locked - Test if CBM or portion is pseudo-locked
 * @d: RDT domain
 * @cbm: CBM to test
 *
 * @d represents a cache instance and @cbm a capacity bitmask that is
 * considered for it. Determine if @cbm overlaps with any existing
 * pseudo-locked region on @d.
 *
 * @cbm is unsigned long, even if only 32 bits are used, to make the
 * bitmap functions work correctly.
 *
 * Return: true if @cbm overlaps with pseudo-locked region on @d, false
 * otherwise.
 */
bool rdtgroup_cbm_overlaps_pseudo_locked(struct rdt_ctrl_domain *d, unsigned long cbm)
{
	unsigned int cbm_len;
	unsigned long cbm_b;

	if (d->plr) {
		cbm_len = d->plr->s->res->cache.cbm_len;
		cbm_b = d->plr->cbm;
		if (bitmap_intersects(&cbm, &cbm_b, cbm_len))
			return true;
	}
	return false;
}

/**
 * rdtgroup_pseudo_locked_in_hierarchy - Pseudo-locked region in cache hierarchy
 * @d: RDT domain under test
 *
 * The setup of a pseudo-locked region affects all cache instances within
 * the hierarchy of the region. It is thus essential to know if any
 * pseudo-locked regions exist within a cache hierarchy to prevent any
 * attempts to create new pseudo-locked regions in the same hierarchy.
 *
 * Return: true if a pseudo-locked region exists in the hierarchy of @d or
 *         if it is not possible to test due to memory allocation issue,
 *         false otherwise.
 */
bool rdtgroup_pseudo_locked_in_hierarchy(struct rdt_ctrl_domain *d)
{
	struct rdt_ctrl_domain *d_i;
	cpumask_var_t cpu_with_psl;
	struct rdt_resource *r;
	bool ret = false;

	/* Walking r->domains, ensure it can't race with cpuhp */
	lockdep_assert_cpus_held();

	if (!zalloc_cpumask_var(&cpu_with_psl, GFP_KERNEL))
		return true;

	/*
	 * First determine which cpus have pseudo-locked regions
	 * associated with them.
	 */
	for_each_alloc_capable_rdt_resource(r) {
		list_for_each_entry(d_i, &r->ctrl_domains, hdr.list) {
			if (d_i->plr)
				cpumask_or(cpu_with_psl, cpu_with_psl,
					   &d_i->hdr.cpu_mask);
		}
	}

	/*
	 * Next test if new pseudo-locked region would intersect with
	 * existing region.
	 */
	if (cpumask_intersects(&d->hdr.cpu_mask, cpu_with_psl))
		ret = true;

	free_cpumask_var(cpu_with_psl);
	return ret;
}

/**
 * pseudo_lock_measure_cycles - Trigger latency measure to pseudo-locked region
 * @rdtgrp: Resource group to which the pseudo-locked region belongs.
 * @sel: Selector of which measurement to perform on a pseudo-locked region.
 *
 * The measurement of latency to access a pseudo-locked region should be
 * done from a cpu that is associated with that pseudo-locked region.
 * Determine which cpu is associated with this region and start a thread on
 * that cpu to perform the measurement, wait for that thread to complete.
 *
 * Return: 0 on success, <0 on failure
 */
static int pseudo_lock_measure_cycles(struct rdtgroup *rdtgrp, int sel)
{
	struct pseudo_lock_region *plr = rdtgrp->plr;
	struct task_struct *thread;
	unsigned int cpu;
	int ret = -1;

	cpus_read_lock();
	mutex_lock(&rdtgroup_mutex);

	if (rdtgrp->flags & RDT_DELETED) {
		ret = -ENODEV;
		goto out;
	}

	if (!plr->d) {
		ret = -ENODEV;
		goto out;
	}

	plr->thread_done = 0;
	cpu = cpumask_first(&plr->d->hdr.cpu_mask);
	if (!cpu_online(cpu)) {
		ret = -ENODEV;
		goto out;
	}

	plr->cpu = cpu;

	if (sel == 1)
		thread = kthread_run_on_cpu(resctrl_arch_measure_cycles_lat_fn,
					    plr, cpu, "pseudo_lock_measure/%u");
	else if (sel == 2)
		thread = kthread_run_on_cpu(resctrl_arch_measure_l2_residency,
					    plr, cpu, "pseudo_lock_measure/%u");
	else if (sel == 3)
		thread = kthread_run_on_cpu(resctrl_arch_measure_l3_residency,
					    plr, cpu, "pseudo_lock_measure/%u");
	else
		goto out;

	if (IS_ERR(thread)) {
		ret = PTR_ERR(thread);
		goto out;
	}

	ret = wait_event_interruptible(plr->lock_thread_wq,
				       plr->thread_done == 1);
	if (ret < 0)
		goto out;

	ret = 0;

out:
	mutex_unlock(&rdtgroup_mutex);
	cpus_read_unlock();
	return ret;
}

static ssize_t pseudo_lock_measure_trigger(struct file *file,
					   const char __user *user_buf,
					   size_t count, loff_t *ppos)
{
	struct rdtgroup *rdtgrp = file->private_data;
	size_t buf_size;
	char buf[32];
	int ret;
	int sel;

	buf_size = min(count, (sizeof(buf) - 1));
	if (copy_from_user(buf, user_buf, buf_size))
		return -EFAULT;

	buf[buf_size] = '\0';
	ret = kstrtoint(buf, 10, &sel);
	if (ret == 0) {
		if (sel != 1 && sel != 2 && sel != 3)
			return -EINVAL;
		ret = pseudo_lock_measure_cycles(rdtgrp, sel);
		if (ret == 0)
			ret = count;
	}

	return ret;
}

static const struct file_operations pseudo_measure_fops = {
	.write = pseudo_lock_measure_trigger,
	.open = simple_open,
	.llseek = default_llseek,
};

/**
 * rdtgroup_pseudo_lock_create - Create a pseudo-locked region
 * @rdtgrp: resource group to which pseudo-lock region belongs
 *
 * Called when a resource group in the pseudo-locksetup mode receives a
 * valid schemata that should be pseudo-locked. Since the resource group is
 * in pseudo-locksetup mode the &struct pseudo_lock_region has already been
 * allocated and initialized with the essential information. If a failure
 * occurs the resource group remains in the pseudo-locksetup mode with the
 * &struct pseudo_lock_region associated with it, but cleared from all
 * information and ready for the user to re-attempt pseudo-locking by
 * writing the schemata again.
 *
 * Return: 0 if the pseudo-locked region was successfully pseudo-locked, <0
 * on failure. Descriptive error will be written to last_cmd_status buffer.
 */
int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp)
{
	struct pseudo_lock_region *plr = rdtgrp->plr;
	struct task_struct *thread;
	unsigned int new_minor;
	struct device *dev;
	char *kn_name __free(kfree) = NULL;
	int ret;

	ret = pseudo_lock_region_alloc(plr);
	if (ret < 0)
		return ret;

	ret = pseudo_lock_cstates_constrain(plr);
	if (ret < 0) {
		ret = -EINVAL;
		goto out_region;
	}
	kn_name = kstrdup(rdt_kn_name(rdtgrp->kn), GFP_KERNEL);
	if (!kn_name) {
		ret = -ENOMEM;
		goto out_cstates;
	}

	plr->thread_done = 0;

	thread = kthread_run_on_cpu(resctrl_arch_pseudo_lock_fn, plr,
				    plr->cpu, "pseudo_lock/%u");
	if (IS_ERR(thread)) {
		ret = PTR_ERR(thread);
		rdt_last_cmd_printf("Locking thread returned error %d\n", ret);
		goto out_cstates;
	}

	ret = wait_event_interruptible(plr->lock_thread_wq,
				       plr->thread_done == 1);
	if (ret < 0) {
		/*
		 * If the thread does not get on the CPU for whatever
		 * reason and the process which sets up the region is
		 * interrupted then this will leave the thread in runnable
		 * state and once it gets on the CPU it will dereference
		 * the cleared, but not freed, plr struct resulting in an
		 * empty pseudo-locking loop.
		 */
		rdt_last_cmd_puts("Locking thread interrupted\n");
		goto out_cstates;
	}

	ret = pseudo_lock_minor_get(&new_minor);
	if (ret < 0) {
		rdt_last_cmd_puts("Unable to obtain a new minor number\n");
		goto out_cstates;
	}

	/*
	 * Unlock access but do not release the reference. The
	 * pseudo-locked region will still be here on return.
	 *
	 * The mutex has to be released temporarily to avoid a potential
	 * deadlock with the mm->mmap_lock which is obtained in the
	 * device_create() and debugfs_create_dir() callpath below as well as
	 * before the mmap() callback is called.
	 */
	mutex_unlock(&rdtgroup_mutex);

	if (!IS_ERR_OR_NULL(debugfs_resctrl)) {
		plr->debugfs_dir = debugfs_create_dir(kn_name, debugfs_resctrl);
		if (!IS_ERR_OR_NULL(plr->debugfs_dir))
			debugfs_create_file("pseudo_lock_measure", 0200,
					    plr->debugfs_dir, rdtgrp,
					    &pseudo_measure_fops);
	}

	dev = device_create(&pseudo_lock_class, NULL,
			    MKDEV(pseudo_lock_major, new_minor),
			    rdtgrp, "%s", kn_name);

	mutex_lock(&rdtgroup_mutex);

	if (IS_ERR(dev)) {
		ret = PTR_ERR(dev);
		rdt_last_cmd_printf("Failed to create character device: %d\n",
				    ret);
		goto out_debugfs;
	}

	/* We released the mutex - check if group was removed while we did so */
	if (rdtgrp->flags & RDT_DELETED) {
		ret = -ENODEV;
		goto out_device;
	}

	plr->minor = new_minor;

	rdtgrp->mode = RDT_MODE_PSEUDO_LOCKED;
	closid_free(rdtgrp->closid);
	rdtgroup_kn_mode_restore(rdtgrp, "cpus", 0444);
	rdtgroup_kn_mode_restore(rdtgrp, "cpus_list", 0444);

	ret = 0;
	goto out;

out_device:
	device_destroy(&pseudo_lock_class, MKDEV(pseudo_lock_major, new_minor));
out_debugfs:
	debugfs_remove_recursive(plr->debugfs_dir);
	pseudo_lock_minor_release(new_minor);
out_cstates:
	pseudo_lock_cstates_relax(plr);
out_region:
	pseudo_lock_region_clear(plr);
out:
	return ret;
}

/**
 * rdtgroup_pseudo_lock_remove - Remove a pseudo-locked region
 * @rdtgrp: resource group to which the pseudo-locked region belongs
 *
 * The removal of a pseudo-locked region can be initiated when the resource
 * group is removed from user space via a "rmdir" from userspace or the
 * unmount of the resctrl filesystem. On removal the resource group does
 * not go back to pseudo-locksetup mode before it is removed, instead it is
 * removed directly. There is thus asymmetry with the creation where the
 * &struct pseudo_lock_region is removed here while it was not created in
 * rdtgroup_pseudo_lock_create().
 *
 * Return: void
 */
void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp)
{
	struct pseudo_lock_region *plr = rdtgrp->plr;

	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
		/*
		 * Default group cannot be a pseudo-locked region so we can
		 * free closid here.
		 */
		closid_free(rdtgrp->closid);
		goto free;
	}

	pseudo_lock_cstates_relax(plr);
	debugfs_remove_recursive(rdtgrp->plr->debugfs_dir);
	device_destroy(&pseudo_lock_class, MKDEV(pseudo_lock_major, plr->minor));
	pseudo_lock_minor_release(plr->minor);

free:
	pseudo_lock_free(rdtgrp);
}

static int pseudo_lock_dev_open(struct inode *inode, struct file *filp)
{
	struct rdtgroup *rdtgrp;

	mutex_lock(&rdtgroup_mutex);

	rdtgrp = region_find_by_minor(iminor(inode));
	if (!rdtgrp) {
		mutex_unlock(&rdtgroup_mutex);
		return -ENODEV;
	}

	filp->private_data = rdtgrp;
	atomic_inc(&rdtgrp->waitcount);
	/* Perform a non-seekable open - llseek is not supported */
	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);

	mutex_unlock(&rdtgroup_mutex);

	return 0;
}

static int pseudo_lock_dev_release(struct inode *inode, struct file *filp)
{
	struct rdtgroup *rdtgrp;

	mutex_lock(&rdtgroup_mutex);
	rdtgrp = filp->private_data;
	WARN_ON(!rdtgrp);
	if (!rdtgrp) {
		mutex_unlock(&rdtgroup_mutex);
		return -ENODEV;
	}
	filp->private_data = NULL;
	atomic_dec(&rdtgrp->waitcount);
	mutex_unlock(&rdtgroup_mutex);
	return 0;
}

static int pseudo_lock_dev_mremap(struct vm_area_struct *area)
{
	/* Not supported */
	return -EINVAL;
}

static const struct vm_operations_struct pseudo_mmap_ops = {
	.mremap = pseudo_lock_dev_mremap,
};

static int pseudo_lock_dev_mmap_prepare(struct vm_area_desc *desc)
{
	unsigned long off = desc->pgoff << PAGE_SHIFT;
	unsigned long vsize = vma_desc_size(desc);
	struct file *filp = desc->file;
	struct pseudo_lock_region *plr;
	struct rdtgroup *rdtgrp;
	unsigned long physical;
	unsigned long psize;

	mutex_lock(&rdtgroup_mutex);

	rdtgrp = filp->private_data;
	WARN_ON(!rdtgrp);
	if (!rdtgrp) {
		mutex_unlock(&rdtgroup_mutex);
		return -ENODEV;
	}

	plr = rdtgrp->plr;

	if (!plr->d) {
		mutex_unlock(&rdtgroup_mutex);
		return -ENODEV;
	}

	/*
	 * Task is required to run with affinity to the cpus associated
	 * with the pseudo-locked region. If this is not the case the task
	 * may be scheduled elsewhere and invalidate entries in the
	 * pseudo-locked region.
	 */
	if (!cpumask_subset(current->cpus_ptr, &plr->d->hdr.cpu_mask)) {
		mutex_unlock(&rdtgroup_mutex);
		return -EINVAL;
	}

	physical = __pa(plr->kmem) >> PAGE_SHIFT;
	psize = plr->size - off;

	if (off > plr->size) {
		mutex_unlock(&rdtgroup_mutex);
		return -ENOSPC;
	}

	/*
	 * Ensure changes are carried directly to the memory being mapped,
	 * do not allow copy-on-write mapping.
	 */
	if (!vma_desc_test_flags(desc, VMA_SHARED_BIT)) {
		mutex_unlock(&rdtgroup_mutex);
		return -EINVAL;
	}

	if (vsize > psize) {
		mutex_unlock(&rdtgroup_mutex);
		return -ENOSPC;
	}

	memset(plr->kmem + off, 0, vsize);

	desc->vm_ops = &pseudo_mmap_ops;
	mmap_action_remap_full(desc, physical + desc->pgoff);

	mutex_unlock(&rdtgroup_mutex);
	return 0;
}

static const struct file_operations pseudo_lock_dev_fops = {
	.owner =	THIS_MODULE,
	.read =		NULL,
	.write =	NULL,
	.open =		pseudo_lock_dev_open,
	.release =	pseudo_lock_dev_release,
	.mmap_prepare =	pseudo_lock_dev_mmap_prepare,
};

int rdt_pseudo_lock_init(void)
{
	int ret;

	ret = register_chrdev(0, "pseudo_lock", &pseudo_lock_dev_fops);
	if (ret < 0)
		return ret;

	pseudo_lock_major = ret;

	ret = class_register(&pseudo_lock_class);
	if (ret) {
		unregister_chrdev(pseudo_lock_major, "pseudo_lock");
		return ret;
	}

	return 0;
}

void rdt_pseudo_lock_release(void)
{
	class_unregister(&pseudo_lock_class);
	unregister_chrdev(pseudo_lock_major, "pseudo_lock");
	pseudo_lock_major = 0;
}