drm/panthor: Don't add write fences to the shared BOs

[drm/drm-misc.git] / arch / x86 / kernel / cpu / 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/cpu.h>
#include <linux/cpumask.h>
#include <linux/debugfs.h>
#include <linux/kthread.h>
#include <linux/mman.h>
#include <linux/perf_event.h>
#include <linux/pm_qos.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

#include <asm/cacheflush.h>
#include <asm/cpu_device_id.h>
#include <asm/resctrl.h>
#include <asm/perf_event.h>

#include "../../events/perf_event.h" /* For X86_CONFIG() */
#include "internal.h"

#define CREATE_TRACE_POINTS
#include "trace.h"

/*
 * The bits needed to disable hardware prefetching varies based on the
 * platform. During initialization we will discover which bits to use.
 */
static u64 prefetch_disable_bits;

/*
 * 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;
        return kasprintf(GFP_KERNEL, "pseudo_lock/%s", rdtgrp->kn->name);
}

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

/**
 * get_prefetch_disable_bits - prefetch disable bits of supported platforms
 * @void: It takes no parameters.
 *
 * Capture the list of platforms that have been validated to support
 * pseudo-locking. This includes testing to ensure pseudo-locked regions
 * with low cache miss rates can be created under variety of load conditions
 * as well as that these pseudo-locked regions can maintain their low cache
 * miss rates under variety of load conditions for significant lengths of time.
 *
 * After a platform has been validated to support pseudo-locking its
 * hardware prefetch disable bits are included here as they are documented
 * in the SDM.
 *
 * When adding a platform here also add support for its cache events to
 * measure_cycles_perf_fn()
 *
 * Return:
 * If platform is supported, the bits to disable hardware prefetchers, 0
 * if platform is not supported.
 */
static u64 get_prefetch_disable_bits(void)
{
        if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
            boot_cpu_data.x86 != 6)
                return 0;

        switch (boot_cpu_data.x86_vfm) {
        case INTEL_BROADWELL_X:
                /*
                 * SDM defines bits of MSR_MISC_FEATURE_CONTROL register
                 * as:
                 * 0    L2 Hardware Prefetcher Disable (R/W)
                 * 1    L2 Adjacent Cache Line Prefetcher Disable (R/W)
                 * 2    DCU Hardware Prefetcher Disable (R/W)
                 * 3    DCU IP Prefetcher Disable (R/W)
                 * 63:4 Reserved
                 */
                return 0xF;
        case INTEL_ATOM_GOLDMONT:
        case INTEL_ATOM_GOLDMONT_PLUS:
                /*
                 * SDM defines bits of MSR_MISC_FEATURE_CONTROL register
                 * as:
                 * 0     L2 Hardware Prefetcher Disable (R/W)
                 * 1     Reserved
                 * 2     DCU Hardware Prefetcher Disable (R/W)
                 * 63:3  Reserved
                 */
                return 0x5;
        }

        return 0;
}

/**
 * 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(sizeof(*pm_req), GFP_KERNEL);
                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(sizeof(*plr), GFP_KERNEL);
        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;
}

/**
 * pseudo_lock_fn - Load kernel memory into cache
 * @_rdtgrp: resource group to which pseudo-lock region belongs
 *
 * This is the core pseudo-locking flow.
 *
 * First we ensure that the kernel memory cannot be found in the cache.
 * Then, while taking care that there will be as little interference as
 * possible, the memory to be loaded is accessed while core is running
 * with class of service set to the bitmask of the pseudo-locked region.
 * After this is complete no future CAT allocations will be allowed to
 * overlap with this bitmask.
 *
 * Local register variables are utilized to ensure that the memory region
 * to be locked is the only memory access made during the critical locking
 * loop.
 *
 * Return: 0. Waiter on waitqueue will be woken on completion.
 */
static int pseudo_lock_fn(void *_rdtgrp)
{
        struct rdtgroup *rdtgrp = _rdtgrp;
        struct pseudo_lock_region *plr = rdtgrp->plr;
        u32 rmid_p, closid_p;
        unsigned long i;
        u64 saved_msr;
#ifdef CONFIG_KASAN
        /*
         * The registers used for local register variables are also used
         * when KASAN is active. When KASAN is active we use a regular
         * variable to ensure we always use a valid pointer, but the cost
         * is that this variable will enter the cache through evicting the
         * memory we are trying to lock into the cache. Thus expect lower
         * pseudo-locking success rate when KASAN is active.
         */
        unsigned int line_size;
        unsigned int size;
        void *mem_r;
#else
        register unsigned int line_size asm("esi");
        register unsigned int size asm("edi");
        register void *mem_r asm(_ASM_BX);
#endif /* CONFIG_KASAN */

        /*
         * Make sure none of the allocated memory is cached. If it is we
         * will get a cache hit in below loop from outside of pseudo-locked
         * region.
         * wbinvd (as opposed to clflush/clflushopt) is required to
         * increase likelihood that allocated cache portion will be filled
         * with associated memory.
         */
        native_wbinvd();

        /*
         * Always called with interrupts enabled. By disabling interrupts
         * ensure that we will not be preempted during this critical section.
         */
        local_irq_disable();

        /*
         * Call wrmsr and rdmsr as directly as possible to avoid tracing
         * clobbering local register variables or affecting cache accesses.
         *
         * Disable the hardware prefetcher so that when the end of the memory
         * being pseudo-locked is reached the hardware will not read beyond
         * the buffer and evict pseudo-locked memory read earlier from the
         * cache.
         */
        saved_msr = __rdmsr(MSR_MISC_FEATURE_CONTROL);
        __wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
        closid_p = this_cpu_read(pqr_state.cur_closid);
        rmid_p = this_cpu_read(pqr_state.cur_rmid);
        mem_r = plr->kmem;
        size = plr->size;
        line_size = plr->line_size;
        /*
         * Critical section begin: start by writing the closid associated
         * with the capacity bitmask of the cache region being
         * pseudo-locked followed by reading of kernel memory to load it
         * into the cache.
         */
        __wrmsr(MSR_IA32_PQR_ASSOC, rmid_p, rdtgrp->closid);
        /*
         * Cache was flushed earlier. Now access kernel memory to read it
         * into cache region associated with just activated plr->closid.
         * Loop over data twice:
         * - In first loop the cache region is shared with the page walker
         *   as it populates the paging structure caches (including TLB).
         * - In the second loop the paging structure caches are used and
         *   cache region is populated with the memory being referenced.
         */
        for (i = 0; i < size; i += PAGE_SIZE) {
                /*
                 * Add a barrier to prevent speculative execution of this
                 * loop reading beyond the end of the buffer.
                 */
                rmb();
                asm volatile("mov (%0,%1,1), %%eax\n\t"
                        :
                        : "r" (mem_r), "r" (i)
                        : "%eax", "memory");
        }
        for (i = 0; i < size; i += line_size) {
                /*
                 * Add a barrier to prevent speculative execution of this
                 * loop reading beyond the end of the buffer.
                 */
                rmb();
                asm volatile("mov (%0,%1,1), %%eax\n\t"
                        :
                        : "r" (mem_r), "r" (i)
                        : "%eax", "memory");
        }
        /*
         * Critical section end: restore closid with capacity bitmask that
         * does not overlap with pseudo-locked region.
         */
        __wrmsr(MSR_IA32_PQR_ASSOC, rmid_p, closid_p);

        /* Re-enable the hardware prefetcher(s) */
        wrmsrl(MSR_MISC_FEATURE_CONTROL, saved_msr);
        local_irq_enable();

        plr->thread_done = 1;
        wake_up_interruptible(&plr->lock_thread_wq);
        return 0;
}

/**
 * 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.
         */
        prefetch_disable_bits = get_prefetch_disable_bits();
        if (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;
}

/**
 * measure_cycles_lat_fn - Measure cycle latency to read pseudo-locked memory
 * @_plr: pseudo-lock region to measure
 *
 * There is no deterministic way to test if a memory region is cached. One
 * way is to measure how long it takes to read the memory, the speed of
 * access is a good way to learn how close to the cpu the data was. Even
 * more, if the prefetcher is disabled and the memory is read at a stride
 * of half the cache line, then a cache miss will be easy to spot since the
 * read of the first half would be significantly slower than the read of
 * the second half.
 *
 * Return: 0. Waiter on waitqueue will be woken on completion.
 */
static int measure_cycles_lat_fn(void *_plr)
{
        struct pseudo_lock_region *plr = _plr;
        u32 saved_low, saved_high;
        unsigned long i;
        u64 start, end;
        void *mem_r;

        local_irq_disable();
        /*
         * Disable hardware prefetchers.
         */
        rdmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
        wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
        mem_r = READ_ONCE(plr->kmem);
        /*
         * Dummy execute of the time measurement to load the needed
         * instructions into the L1 instruction cache.
         */
        start = rdtsc_ordered();
        for (i = 0; i < plr->size; i += 32) {
                start = rdtsc_ordered();
                asm volatile("mov (%0,%1,1), %%eax\n\t"
                             :
                             : "r" (mem_r), "r" (i)
                             : "%eax", "memory");
                end = rdtsc_ordered();
                trace_pseudo_lock_mem_latency((u32)(end - start));
        }
        wrmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
        local_irq_enable();
        plr->thread_done = 1;
        wake_up_interruptible(&plr->lock_thread_wq);
        return 0;
}

/*
 * Create a perf_event_attr for the hit and miss perf events that will
 * be used during the performance measurement. A perf_event maintains
 * a pointer to its perf_event_attr so a unique attribute structure is
 * created for each perf_event.
 *
 * The actual configuration of the event is set right before use in order
 * to use the X86_CONFIG macro.
 */
static struct perf_event_attr perf_miss_attr = {
        .type           = PERF_TYPE_RAW,
        .size           = sizeof(struct perf_event_attr),
        .pinned         = 1,
        .disabled       = 0,
        .exclude_user   = 1,
};

static struct perf_event_attr perf_hit_attr = {
        .type           = PERF_TYPE_RAW,
        .size           = sizeof(struct perf_event_attr),
        .pinned         = 1,
        .disabled       = 0,
        .exclude_user   = 1,
};

struct residency_counts {
        u64 miss_before, hits_before;
        u64 miss_after,  hits_after;
};

static int measure_residency_fn(struct perf_event_attr *miss_attr,
                                struct perf_event_attr *hit_attr,
                                struct pseudo_lock_region *plr,
                                struct residency_counts *counts)
{
        u64 hits_before = 0, hits_after = 0, miss_before = 0, miss_after = 0;
        struct perf_event *miss_event, *hit_event;
        int hit_pmcnum, miss_pmcnum;
        u32 saved_low, saved_high;
        unsigned int line_size;
        unsigned int size;
        unsigned long i;
        void *mem_r;
        u64 tmp;

        miss_event = perf_event_create_kernel_counter(miss_attr, plr->cpu,
                                                      NULL, NULL, NULL);
        if (IS_ERR(miss_event))
                goto out;

        hit_event = perf_event_create_kernel_counter(hit_attr, plr->cpu,
                                                     NULL, NULL, NULL);
        if (IS_ERR(hit_event))
                goto out_miss;

        local_irq_disable();
        /*
         * Check any possible error state of events used by performing
         * one local read.
         */
        if (perf_event_read_local(miss_event, &tmp, NULL, NULL)) {
                local_irq_enable();
                goto out_hit;
        }
        if (perf_event_read_local(hit_event, &tmp, NULL, NULL)) {
                local_irq_enable();
                goto out_hit;
        }

        /*
         * Disable hardware prefetchers.
         */
        rdmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
        wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);

        /* Initialize rest of local variables */
        /*
         * Performance event has been validated right before this with
         * interrupts disabled - it is thus safe to read the counter index.
         */
        miss_pmcnum = x86_perf_rdpmc_index(miss_event);
        hit_pmcnum = x86_perf_rdpmc_index(hit_event);
        line_size = READ_ONCE(plr->line_size);
        mem_r = READ_ONCE(plr->kmem);
        size = READ_ONCE(plr->size);

        /*
         * Read counter variables twice - first to load the instructions
         * used in L1 cache, second to capture accurate value that does not
         * include cache misses incurred because of instruction loads.
         */
        rdpmcl(hit_pmcnum, hits_before);
        rdpmcl(miss_pmcnum, miss_before);
        /*
         * From SDM: Performing back-to-back fast reads are not guaranteed
         * to be monotonic.
         * Use LFENCE to ensure all previous instructions are retired
         * before proceeding.
         */
        rmb();
        rdpmcl(hit_pmcnum, hits_before);
        rdpmcl(miss_pmcnum, miss_before);
        /*
         * Use LFENCE to ensure all previous instructions are retired
         * before proceeding.
         */
        rmb();
        for (i = 0; i < size; i += line_size) {
                /*
                 * Add a barrier to prevent speculative execution of this
                 * loop reading beyond the end of the buffer.
                 */
                rmb();
                asm volatile("mov (%0,%1,1), %%eax\n\t"
                             :
                             : "r" (mem_r), "r" (i)
                             : "%eax", "memory");
        }
        /*
         * Use LFENCE to ensure all previous instructions are retired
         * before proceeding.
         */
        rmb();
        rdpmcl(hit_pmcnum, hits_after);
        rdpmcl(miss_pmcnum, miss_after);
        /*
         * Use LFENCE to ensure all previous instructions are retired
         * before proceeding.
         */
        rmb();
        /* Re-enable hardware prefetchers */
        wrmsr(MSR_MISC_FEATURE_CONTROL, saved_low, saved_high);
        local_irq_enable();
out_hit:
        perf_event_release_kernel(hit_event);
out_miss:
        perf_event_release_kernel(miss_event);
out:
        /*
         * All counts will be zero on failure.
         */
        counts->miss_before = miss_before;
        counts->hits_before = hits_before;
        counts->miss_after  = miss_after;
        counts->hits_after  = hits_after;
        return 0;
}

static int measure_l2_residency(void *_plr)
{
        struct pseudo_lock_region *plr = _plr;
        struct residency_counts counts = {0};

        /*
         * Non-architectural event for the Goldmont Microarchitecture
         * from Intel x86 Architecture Software Developer Manual (SDM):
         * MEM_LOAD_UOPS_RETIRED D1H (event number)
         * Umask values:
         *     L2_HIT   02H
         *     L2_MISS  10H
         */
        switch (boot_cpu_data.x86_vfm) {
        case INTEL_ATOM_GOLDMONT:
        case INTEL_ATOM_GOLDMONT_PLUS:
                perf_miss_attr.config = X86_CONFIG(.event = 0xd1,
                                                   .umask = 0x10);
                perf_hit_attr.config = X86_CONFIG(.event = 0xd1,
                                                  .umask = 0x2);
                break;
        default:
                goto out;
        }

        measure_residency_fn(&perf_miss_attr, &perf_hit_attr, plr, &counts);
        /*
         * If a failure prevented the measurements from succeeding
         * tracepoints will still be written and all counts will be zero.
         */
        trace_pseudo_lock_l2(counts.hits_after - counts.hits_before,
                             counts.miss_after - counts.miss_before);
out:
        plr->thread_done = 1;
        wake_up_interruptible(&plr->lock_thread_wq);
        return 0;
}

static int measure_l3_residency(void *_plr)
{
        struct pseudo_lock_region *plr = _plr;
        struct residency_counts counts = {0};

        /*
         * On Broadwell Microarchitecture the MEM_LOAD_UOPS_RETIRED event
         * has two "no fix" errata associated with it: BDM35 and BDM100. On
         * this platform the following events are used instead:
         * LONGEST_LAT_CACHE 2EH (Documented in SDM)
         *       REFERENCE 4FH
         *       MISS      41H
         */

        switch (boot_cpu_data.x86_vfm) {
        case INTEL_BROADWELL_X:
                /* On BDW the hit event counts references, not hits */
                perf_hit_attr.config = X86_CONFIG(.event = 0x2e,
                                                  .umask = 0x4f);
                perf_miss_attr.config = X86_CONFIG(.event = 0x2e,
                                                   .umask = 0x41);
                break;
        default:
                goto out;
        }

        measure_residency_fn(&perf_miss_attr, &perf_hit_attr, plr, &counts);
        /*
         * If a failure prevented the measurements from succeeding
         * tracepoints will still be written and all counts will be zero.
         */

        counts.miss_after -= counts.miss_before;
        if (boot_cpu_data.x86_vfm == INTEL_BROADWELL_X) {
                /*
                 * On BDW references and misses are counted, need to adjust.
                 * Sometimes the "hits" counter is a bit more than the
                 * references, for example, x references but x + 1 hits.
                 * To not report invalid hit values in this case we treat
                 * that as misses equal to references.
                 */
                /* First compute the number of cache references measured */
                counts.hits_after -= counts.hits_before;
                /* Next convert references to cache hits */
                counts.hits_after -= min(counts.miss_after, counts.hits_after);
        } else {
                counts.hits_after -= counts.hits_before;
        }

        trace_pseudo_lock_l3(counts.hits_after, counts.miss_after);
out:
        plr->thread_done = 1;
        wake_up_interruptible(&plr->lock_thread_wq);
        return 0;
}

/**
 * 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_create_on_node(measure_cycles_lat_fn, plr,
                                                cpu_to_node(cpu),
                                                "pseudo_lock_measure/%u",
                                                cpu);
        else if (sel == 2)
                thread = kthread_create_on_node(measure_l2_residency, plr,
                                                cpu_to_node(cpu),
                                                "pseudo_lock_measure/%u",
                                                cpu);
        else if (sel == 3)
                thread = kthread_create_on_node(measure_l3_residency, plr,
                                                cpu_to_node(cpu),
                                                "pseudo_lock_measure/%u",
                                                cpu);
        else
                goto out;

        if (IS_ERR(thread)) {
                ret = PTR_ERR(thread);
                goto out;
        }
        kthread_bind(thread, cpu);
        wake_up_process(thread);

        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 = debugfs_file_get(file->f_path.dentry);
                if (ret)
                        return ret;
                ret = pseudo_lock_measure_cycles(rdtgrp, sel);
                if (ret == 0)
                        ret = count;
                debugfs_file_put(file->f_path.dentry);
        }

        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;
        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;
        }

        plr->thread_done = 0;

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

        kthread_bind(thread, plr->cpu);
        wake_up_process(thread);

        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(rdtgrp->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", rdtgrp->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(struct file *filp, struct vm_area_struct *vma)
{
        unsigned long vsize = vma->vm_end - vma->vm_start;
        unsigned long off = vma->vm_pgoff << PAGE_SHIFT;
        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->vm_flags & VM_SHARED)) {
                mutex_unlock(&rdtgroup_mutex);
                return -EINVAL;
        }

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

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

        if (remap_pfn_range(vma, vma->vm_start, physical + vma->vm_pgoff,
                            vsize, vma->vm_page_prot)) {
                mutex_unlock(&rdtgroup_mutex);
                return -EAGAIN;
        }
        vma->vm_ops = &pseudo_mmap_ops;
        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 =         pseudo_lock_dev_mmap,
};

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;
}