linux/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Resource Director Technology (RDT)
   4 *
   5 * Pseudo-locking support built on top of Cache Allocation Technology (CAT)
   6 *
   7 * Copyright (C) 2018 Intel Corporation
   8 *
   9 * Author: Reinette Chatre <reinette.chatre@intel.com>
  10 */
  11
  12#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
  13
  14#include <linux/cacheinfo.h>
  15#include <linux/cpu.h>
  16#include <linux/cpumask.h>
  17#include <linux/debugfs.h>
  18#include <linux/kthread.h>
  19#include <linux/mman.h>
  20#include <linux/perf_event.h>
  21#include <linux/pm_qos.h>
  22#include <linux/slab.h>
  23#include <linux/uaccess.h>
  24
  25#include <asm/cacheflush.h>
  26#include <asm/intel-family.h>
  27#include <asm/resctrl.h>
  28#include <asm/perf_event.h>
  29
  30#include "../../events/perf_event.h" /* For X86_CONFIG() */
  31#include "internal.h"
  32
  33#define CREATE_TRACE_POINTS
  34#include "pseudo_lock_event.h"
  35
  36/*
  37 * The bits needed to disable hardware prefetching varies based on the
  38 * platform. During initialization we will discover which bits to use.
  39 */
  40static u64 prefetch_disable_bits;
  41
  42/*
  43 * Major number assigned to and shared by all devices exposing
  44 * pseudo-locked regions.
  45 */
  46static unsigned int pseudo_lock_major;
  47static unsigned long pseudo_lock_minor_avail = GENMASK(MINORBITS, 0);
  48static struct class *pseudo_lock_class;
  49
  50/**
  51 * get_prefetch_disable_bits - prefetch disable bits of supported platforms
  52 * @void: It takes no parameters.
  53 *
  54 * Capture the list of platforms that have been validated to support
  55 * pseudo-locking. This includes testing to ensure pseudo-locked regions
  56 * with low cache miss rates can be created under variety of load conditions
  57 * as well as that these pseudo-locked regions can maintain their low cache
  58 * miss rates under variety of load conditions for significant lengths of time.
  59 *
  60 * After a platform has been validated to support pseudo-locking its
  61 * hardware prefetch disable bits are included here as they are documented
  62 * in the SDM.
  63 *
  64 * When adding a platform here also add support for its cache events to
  65 * measure_cycles_perf_fn()
  66 *
  67 * Return:
  68 * If platform is supported, the bits to disable hardware prefetchers, 0
  69 * if platform is not supported.
  70 */
  71static u64 get_prefetch_disable_bits(void)
  72{
  73        if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
  74            boot_cpu_data.x86 != 6)
  75                return 0;
  76
  77        switch (boot_cpu_data.x86_model) {
  78        case INTEL_FAM6_BROADWELL_X:
  79                /*
  80                 * SDM defines bits of MSR_MISC_FEATURE_CONTROL register
  81                 * as:
  82                 * 0    L2 Hardware Prefetcher Disable (R/W)
  83                 * 1    L2 Adjacent Cache Line Prefetcher Disable (R/W)
  84                 * 2    DCU Hardware Prefetcher Disable (R/W)
  85                 * 3    DCU IP Prefetcher Disable (R/W)
  86                 * 63:4 Reserved
  87                 */
  88                return 0xF;
  89        case INTEL_FAM6_ATOM_GOLDMONT:
  90        case INTEL_FAM6_ATOM_GOLDMONT_PLUS:
  91                /*
  92                 * SDM defines bits of MSR_MISC_FEATURE_CONTROL register
  93                 * as:
  94                 * 0     L2 Hardware Prefetcher Disable (R/W)
  95                 * 1     Reserved
  96                 * 2     DCU Hardware Prefetcher Disable (R/W)
  97                 * 63:3  Reserved
  98                 */
  99                return 0x5;
 100        }
 101
 102        return 0;
 103}
 104
 105/**
 106 * pseudo_lock_minor_get - Obtain available minor number
 107 * @minor: Pointer to where new minor number will be stored
 108 *
 109 * A bitmask is used to track available minor numbers. Here the next free
 110 * minor number is marked as unavailable and returned.
 111 *
 112 * Return: 0 on success, <0 on failure.
 113 */
 114static int pseudo_lock_minor_get(unsigned int *minor)
 115{
 116        unsigned long first_bit;
 117
 118        first_bit = find_first_bit(&pseudo_lock_minor_avail, MINORBITS);
 119
 120        if (first_bit == MINORBITS)
 121                return -ENOSPC;
 122
 123        __clear_bit(first_bit, &pseudo_lock_minor_avail);
 124        *minor = first_bit;
 125
 126        return 0;
 127}
 128
 129/**
 130 * pseudo_lock_minor_release - Return minor number to available
 131 * @minor: The minor number made available
 132 */
 133static void pseudo_lock_minor_release(unsigned int minor)
 134{
 135        __set_bit(minor, &pseudo_lock_minor_avail);
 136}
 137
 138/**
 139 * region_find_by_minor - Locate a pseudo-lock region by inode minor number
 140 * @minor: The minor number of the device representing pseudo-locked region
 141 *
 142 * When the character device is accessed we need to determine which
 143 * pseudo-locked region it belongs to. This is done by matching the minor
 144 * number of the device to the pseudo-locked region it belongs.
 145 *
 146 * Minor numbers are assigned at the time a pseudo-locked region is associated
 147 * with a cache instance.
 148 *
 149 * Return: On success return pointer to resource group owning the pseudo-locked
 150 *         region, NULL on failure.
 151 */
 152static struct rdtgroup *region_find_by_minor(unsigned int minor)
 153{
 154        struct rdtgroup *rdtgrp, *rdtgrp_match = NULL;
 155
 156        list_for_each_entry(rdtgrp, &rdt_all_groups, rdtgroup_list) {
 157                if (rdtgrp->plr && rdtgrp->plr->minor == minor) {
 158                        rdtgrp_match = rdtgrp;
 159                        break;
 160                }
 161        }
 162        return rdtgrp_match;
 163}
 164
 165/**
 166 * struct pseudo_lock_pm_req - A power management QoS request list entry
 167 * @list:       Entry within the @pm_reqs list for a pseudo-locked region
 168 * @req:        PM QoS request
 169 */
 170struct pseudo_lock_pm_req {
 171        struct list_head list;
 172        struct dev_pm_qos_request req;
 173};
 174
 175static void pseudo_lock_cstates_relax(struct pseudo_lock_region *plr)
 176{
 177        struct pseudo_lock_pm_req *pm_req, *next;
 178
 179        list_for_each_entry_safe(pm_req, next, &plr->pm_reqs, list) {
 180                dev_pm_qos_remove_request(&pm_req->req);
 181                list_del(&pm_req->list);
 182                kfree(pm_req);
 183        }
 184}
 185
 186/**
 187 * pseudo_lock_cstates_constrain - Restrict cores from entering C6
 188 * @plr: Pseudo-locked region
 189 *
 190 * To prevent the cache from being affected by power management entering
 191 * C6 has to be avoided. This is accomplished by requesting a latency
 192 * requirement lower than lowest C6 exit latency of all supported
 193 * platforms as found in the cpuidle state tables in the intel_idle driver.
 194 * At this time it is possible to do so with a single latency requirement
 195 * for all supported platforms.
 196 *
 197 * Since Goldmont is supported, which is affected by X86_BUG_MONITOR,
 198 * the ACPI latencies need to be considered while keeping in mind that C2
 199 * may be set to map to deeper sleep states. In this case the latency
 200 * requirement needs to prevent entering C2 also.
 201 *
 202 * Return: 0 on success, <0 on failure
 203 */
 204static int pseudo_lock_cstates_constrain(struct pseudo_lock_region *plr)
 205{
 206        struct pseudo_lock_pm_req *pm_req;
 207        int cpu;
 208        int ret;
 209
 210        for_each_cpu(cpu, &plr->d->cpu_mask) {
 211                pm_req = kzalloc(sizeof(*pm_req), GFP_KERNEL);
 212                if (!pm_req) {
 213                        rdt_last_cmd_puts("Failure to allocate memory for PM QoS\n");
 214                        ret = -ENOMEM;
 215                        goto out_err;
 216                }
 217                ret = dev_pm_qos_add_request(get_cpu_device(cpu),
 218                                             &pm_req->req,
 219                                             DEV_PM_QOS_RESUME_LATENCY,
 220                                             30);
 221                if (ret < 0) {
 222                        rdt_last_cmd_printf("Failed to add latency req CPU%d\n",
 223                                            cpu);
 224                        kfree(pm_req);
 225                        ret = -1;
 226                        goto out_err;
 227                }
 228                list_add(&pm_req->list, &plr->pm_reqs);
 229        }
 230
 231        return 0;
 232
 233out_err:
 234        pseudo_lock_cstates_relax(plr);
 235        return ret;
 236}
 237
 238/**
 239 * pseudo_lock_region_clear - Reset pseudo-lock region data
 240 * @plr: pseudo-lock region
 241 *
 242 * All content of the pseudo-locked region is reset - any memory allocated
 243 * freed.
 244 *
 245 * Return: void
 246 */
 247static void pseudo_lock_region_clear(struct pseudo_lock_region *plr)
 248{
 249        plr->size = 0;
 250        plr->line_size = 0;
 251        kfree(plr->kmem);
 252        plr->kmem = NULL;
 253        plr->r = NULL;
 254        if (plr->d)
 255                plr->d->plr = NULL;
 256        plr->d = NULL;
 257        plr->cbm = 0;
 258        plr->debugfs_dir = NULL;
 259}
 260
 261/**
 262 * pseudo_lock_region_init - Initialize pseudo-lock region information
 263 * @plr: pseudo-lock region
 264 *
 265 * Called after user provided a schemata to be pseudo-locked. From the
 266 * schemata the &struct pseudo_lock_region is on entry already initialized
 267 * with the resource, domain, and capacity bitmask. Here the information
 268 * required for pseudo-locking is deduced from this data and &struct
 269 * pseudo_lock_region initialized further. This information includes:
 270 * - size in bytes of the region to be pseudo-locked
 271 * - cache line size to know the stride with which data needs to be accessed
 272 *   to be pseudo-locked
 273 * - a cpu associated with the cache instance on which the pseudo-locking
 274 *   flow can be executed
 275 *
 276 * Return: 0 on success, <0 on failure. Descriptive error will be written
 277 * to last_cmd_status buffer.
 278 */
 279static int pseudo_lock_region_init(struct pseudo_lock_region *plr)
 280{
 281        struct cpu_cacheinfo *ci;
 282        int ret;
 283        int i;
 284
 285        /* Pick the first cpu we find that is associated with the cache. */
 286        plr->cpu = cpumask_first(&plr->d->cpu_mask);
 287
 288        if (!cpu_online(plr->cpu)) {
 289                rdt_last_cmd_printf("CPU %u associated with cache not online\n",
 290                                    plr->cpu);
 291                ret = -ENODEV;
 292                goto out_region;
 293        }
 294
 295        ci = get_cpu_cacheinfo(plr->cpu);
 296
 297        plr->size = rdtgroup_cbm_to_size(plr->r, plr->d, plr->cbm);
 298
 299        for (i = 0; i < ci->num_leaves; i++) {
 300                if (ci->info_list[i].level == plr->r->cache_level) {
 301                        plr->line_size = ci->info_list[i].coherency_line_size;
 302                        return 0;
 303                }
 304        }
 305
 306        ret = -1;
 307        rdt_last_cmd_puts("Unable to determine cache line size\n");
 308out_region:
 309        pseudo_lock_region_clear(plr);
 310        return ret;
 311}
 312
 313/**
 314 * pseudo_lock_init - Initialize a pseudo-lock region
 315 * @rdtgrp: resource group to which new pseudo-locked region will belong
 316 *
 317 * A pseudo-locked region is associated with a resource group. When this
 318 * association is created the pseudo-locked region is initialized. The
 319 * details of the pseudo-locked region are not known at this time so only
 320 * allocation is done and association established.
 321 *
 322 * Return: 0 on success, <0 on failure
 323 */
 324static int pseudo_lock_init(struct rdtgroup *rdtgrp)
 325{
 326        struct pseudo_lock_region *plr;
 327
 328        plr = kzalloc(sizeof(*plr), GFP_KERNEL);
 329        if (!plr)
 330                return -ENOMEM;
 331
 332        init_waitqueue_head(&plr->lock_thread_wq);
 333        INIT_LIST_HEAD(&plr->pm_reqs);
 334        rdtgrp->plr = plr;
 335        return 0;
 336}
 337
 338/**
 339 * pseudo_lock_region_alloc - Allocate kernel memory that will be pseudo-locked
 340 * @plr: pseudo-lock region
 341 *
 342 * Initialize the details required to set up the pseudo-locked region and
 343 * allocate the contiguous memory that will be pseudo-locked to the cache.
 344 *
 345 * Return: 0 on success, <0 on failure.  Descriptive error will be written
 346 * to last_cmd_status buffer.
 347 */
 348static int pseudo_lock_region_alloc(struct pseudo_lock_region *plr)
 349{
 350        int ret;
 351
 352        ret = pseudo_lock_region_init(plr);
 353        if (ret < 0)
 354                return ret;
 355
 356        /*
 357         * We do not yet support contiguous regions larger than
 358         * KMALLOC_MAX_SIZE.
 359         */
 360        if (plr->size > KMALLOC_MAX_SIZE) {
 361                rdt_last_cmd_puts("Requested region exceeds maximum size\n");
 362                ret = -E2BIG;
 363                goto out_region;
 364        }
 365
 366        plr->kmem = kzalloc(plr->size, GFP_KERNEL);
 367        if (!plr->kmem) {
 368                rdt_last_cmd_puts("Unable to allocate memory\n");
 369                ret = -ENOMEM;
 370                goto out_region;
 371        }
 372
 373        ret = 0;
 374        goto out;
 375out_region:
 376        pseudo_lock_region_clear(plr);
 377out:
 378        return ret;
 379}
 380
 381/**
 382 * pseudo_lock_free - Free a pseudo-locked region
 383 * @rdtgrp: resource group to which pseudo-locked region belonged
 384 *
 385 * The pseudo-locked region's resources have already been released, or not
 386 * yet created at this point. Now it can be freed and disassociated from the
 387 * resource group.
 388 *
 389 * Return: void
 390 */
 391static void pseudo_lock_free(struct rdtgroup *rdtgrp)
 392{
 393        pseudo_lock_region_clear(rdtgrp->plr);
 394        kfree(rdtgrp->plr);
 395        rdtgrp->plr = NULL;
 396}
 397
 398/**
 399 * pseudo_lock_fn - Load kernel memory into cache
 400 * @_rdtgrp: resource group to which pseudo-lock region belongs
 401 *
 402 * This is the core pseudo-locking flow.
 403 *
 404 * First we ensure that the kernel memory cannot be found in the cache.
 405 * Then, while taking care that there will be as little interference as
 406 * possible, the memory to be loaded is accessed while core is running
 407 * with class of service set to the bitmask of the pseudo-locked region.
 408 * After this is complete no future CAT allocations will be allowed to
 409 * overlap with this bitmask.
 410 *
 411 * Local register variables are utilized to ensure that the memory region
 412 * to be locked is the only memory access made during the critical locking
 413 * loop.
 414 *
 415 * Return: 0. Waiter on waitqueue will be woken on completion.
 416 */
 417static int pseudo_lock_fn(void *_rdtgrp)
 418{
 419        struct rdtgroup *rdtgrp = _rdtgrp;
 420        struct pseudo_lock_region *plr = rdtgrp->plr;
 421        u32 rmid_p, closid_p;
 422        unsigned long i;
 423#ifdef CONFIG_KASAN
 424        /*
 425         * The registers used for local register variables are also used
 426         * when KASAN is active. When KASAN is active we use a regular
 427         * variable to ensure we always use a valid pointer, but the cost
 428         * is that this variable will enter the cache through evicting the
 429         * memory we are trying to lock into the cache. Thus expect lower
 430         * pseudo-locking success rate when KASAN is active.
 431         */
 432        unsigned int line_size;
 433        unsigned int size;
 434        void *mem_r;
 435#else
 436        register unsigned int line_size asm("esi");
 437        register unsigned int size asm("edi");
 438        register void *mem_r asm(_ASM_BX);
 439#endif /* CONFIG_KASAN */
 440
 441        /*
 442         * Make sure none of the allocated memory is cached. If it is we
 443         * will get a cache hit in below loop from outside of pseudo-locked
 444         * region.
 445         * wbinvd (as opposed to clflush/clflushopt) is required to
 446         * increase likelihood that allocated cache portion will be filled
 447         * with associated memory.
 448         */
 449        native_wbinvd();
 450
 451        /*
 452         * Always called with interrupts enabled. By disabling interrupts
 453         * ensure that we will not be preempted during this critical section.
 454         */
 455        local_irq_disable();
 456
 457        /*
 458         * Call wrmsr and rdmsr as directly as possible to avoid tracing
 459         * clobbering local register variables or affecting cache accesses.
 460         *
 461         * Disable the hardware prefetcher so that when the end of the memory
 462         * being pseudo-locked is reached the hardware will not read beyond
 463         * the buffer and evict pseudo-locked memory read earlier from the
 464         * cache.
 465         */
 466        __wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
 467        closid_p = this_cpu_read(pqr_state.cur_closid);
 468        rmid_p = this_cpu_read(pqr_state.cur_rmid);
 469        mem_r = plr->kmem;
 470        size = plr->size;
 471        line_size = plr->line_size;
 472        /*
 473         * Critical section begin: start by writing the closid associated
 474         * with the capacity bitmask of the cache region being
 475         * pseudo-locked followed by reading of kernel memory to load it
 476         * into the cache.
 477         */
 478        __wrmsr(IA32_PQR_ASSOC, rmid_p, rdtgrp->closid);
 479        /*
 480         * Cache was flushed earlier. Now access kernel memory to read it
 481         * into cache region associated with just activated plr->closid.
 482         * Loop over data twice:
 483         * - In first loop the cache region is shared with the page walker
 484         *   as it populates the paging structure caches (including TLB).
 485         * - In the second loop the paging structure caches are used and
 486         *   cache region is populated with the memory being referenced.
 487         */
 488        for (i = 0; i < size; i += PAGE_SIZE) {
 489                /*
 490                 * Add a barrier to prevent speculative execution of this
 491                 * loop reading beyond the end of the buffer.
 492                 */
 493                rmb();
 494                asm volatile("mov (%0,%1,1), %%eax\n\t"
 495                        :
 496                        : "r" (mem_r), "r" (i)
 497                        : "%eax", "memory");
 498        }
 499        for (i = 0; i < size; i += line_size) {
 500                /*
 501                 * Add a barrier to prevent speculative execution of this
 502                 * loop reading beyond the end of the buffer.
 503                 */
 504                rmb();
 505                asm volatile("mov (%0,%1,1), %%eax\n\t"
 506                        :
 507                        : "r" (mem_r), "r" (i)
 508                        : "%eax", "memory");
 509        }
 510        /*
 511         * Critical section end: restore closid with capacity bitmask that
 512         * does not overlap with pseudo-locked region.
 513         */
 514        __wrmsr(IA32_PQR_ASSOC, rmid_p, closid_p);
 515
 516        /* Re-enable the hardware prefetcher(s) */
 517        wrmsr(MSR_MISC_FEATURE_CONTROL, 0x0, 0x0);
 518        local_irq_enable();
 519
 520        plr->thread_done = 1;
 521        wake_up_interruptible(&plr->lock_thread_wq);
 522        return 0;
 523}
 524
 525/**
 526 * rdtgroup_monitor_in_progress - Test if monitoring in progress
 527 * @rdtgrp: resource group being queried
 528 *
 529 * Return: 1 if monitor groups have been created for this resource
 530 * group, 0 otherwise.
 531 */
 532static int rdtgroup_monitor_in_progress(struct rdtgroup *rdtgrp)
 533{
 534        return !list_empty(&rdtgrp->mon.crdtgrp_list);
 535}
 536
 537/**
 538 * rdtgroup_locksetup_user_restrict - Restrict user access to group
 539 * @rdtgrp: resource group needing access restricted
 540 *
 541 * A resource group used for cache pseudo-locking cannot have cpus or tasks
 542 * assigned to it. This is communicated to the user by restricting access
 543 * to all the files that can be used to make such changes.
 544 *
 545 * Permissions restored with rdtgroup_locksetup_user_restore()
 546 *
 547 * Return: 0 on success, <0 on failure. If a failure occurs during the
 548 * restriction of access an attempt will be made to restore permissions but
 549 * the state of the mode of these files will be uncertain when a failure
 550 * occurs.
 551 */
 552static int rdtgroup_locksetup_user_restrict(struct rdtgroup *rdtgrp)
 553{
 554        int ret;
 555
 556        ret = rdtgroup_kn_mode_restrict(rdtgrp, "tasks");
 557        if (ret)
 558                return ret;
 559
 560        ret = rdtgroup_kn_mode_restrict(rdtgrp, "cpus");
 561        if (ret)
 562                goto err_tasks;
 563
 564        ret = rdtgroup_kn_mode_restrict(rdtgrp, "cpus_list");
 565        if (ret)
 566                goto err_cpus;
 567
 568        if (rdt_mon_capable) {
 569                ret = rdtgroup_kn_mode_restrict(rdtgrp, "mon_groups");
 570                if (ret)
 571                        goto err_cpus_list;
 572        }
 573
 574        ret = 0;
 575        goto out;
 576
 577err_cpus_list:
 578        rdtgroup_kn_mode_restore(rdtgrp, "cpus_list", 0777);
 579err_cpus:
 580        rdtgroup_kn_mode_restore(rdtgrp, "cpus", 0777);
 581err_tasks:
 582        rdtgroup_kn_mode_restore(rdtgrp, "tasks", 0777);
 583out:
 584        return ret;
 585}
 586
 587/**
 588 * rdtgroup_locksetup_user_restore - Restore user access to group
 589 * @rdtgrp: resource group needing access restored
 590 *
 591 * Restore all file access previously removed using
 592 * rdtgroup_locksetup_user_restrict()
 593 *
 594 * Return: 0 on success, <0 on failure.  If a failure occurs during the
 595 * restoration of access an attempt will be made to restrict permissions
 596 * again but the state of the mode of these files will be uncertain when
 597 * a failure occurs.
 598 */
 599static int rdtgroup_locksetup_user_restore(struct rdtgroup *rdtgrp)
 600{
 601        int ret;
 602
 603        ret = rdtgroup_kn_mode_restore(rdtgrp, "tasks", 0777);
 604        if (ret)
 605                return ret;
 606
 607        ret = rdtgroup_kn_mode_restore(rdtgrp, "cpus", 0777);
 608        if (ret)
 609                goto err_tasks;
 610
 611        ret = rdtgroup_kn_mode_restore(rdtgrp, "cpus_list", 0777);
 612        if (ret)
 613                goto err_cpus;
 614
 615        if (rdt_mon_capable) {
 616                ret = rdtgroup_kn_mode_restore(rdtgrp, "mon_groups", 0777);
 617                if (ret)
 618                        goto err_cpus_list;
 619        }
 620
 621        ret = 0;
 622        goto out;
 623
 624err_cpus_list:
 625        rdtgroup_kn_mode_restrict(rdtgrp, "cpus_list");
 626err_cpus:
 627        rdtgroup_kn_mode_restrict(rdtgrp, "cpus");
 628err_tasks:
 629        rdtgroup_kn_mode_restrict(rdtgrp, "tasks");
 630out:
 631        return ret;
 632}
 633
 634/**
 635 * rdtgroup_locksetup_enter - Resource group enters locksetup mode
 636 * @rdtgrp: resource group requested to enter locksetup mode
 637 *
 638 * A resource group enters locksetup mode to reflect that it would be used
 639 * to represent a pseudo-locked region and is in the process of being set
 640 * up to do so. A resource group used for a pseudo-locked region would
 641 * lose the closid associated with it so we cannot allow it to have any
 642 * tasks or cpus assigned nor permit tasks or cpus to be assigned in the
 643 * future. Monitoring of a pseudo-locked region is not allowed either.
 644 *
 645 * The above and more restrictions on a pseudo-locked region are checked
 646 * for and enforced before the resource group enters the locksetup mode.
 647 *
 648 * Returns: 0 if the resource group successfully entered locksetup mode, <0
 649 * on failure. On failure the last_cmd_status buffer is updated with text to
 650 * communicate details of failure to the user.
 651 */
 652int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp)
 653{
 654        int ret;
 655
 656        /*
 657         * The default resource group can neither be removed nor lose the
 658         * default closid associated with it.
 659         */
 660        if (rdtgrp == &rdtgroup_default) {
 661                rdt_last_cmd_puts("Cannot pseudo-lock default group\n");
 662                return -EINVAL;
 663        }
 664
 665        /*
 666         * Cache Pseudo-locking not supported when CDP is enabled.
 667         *
 668         * Some things to consider if you would like to enable this
 669         * support (using L3 CDP as example):
 670         * - When CDP is enabled two separate resources are exposed,
 671         *   L3DATA and L3CODE, but they are actually on the same cache.
 672         *   The implication for pseudo-locking is that if a
 673         *   pseudo-locked region is created on a domain of one
 674         *   resource (eg. L3CODE), then a pseudo-locked region cannot
 675         *   be created on that same domain of the other resource
 676         *   (eg. L3DATA). This is because the creation of a
 677         *   pseudo-locked region involves a call to wbinvd that will
 678         *   affect all cache allocations on particular domain.
 679         * - Considering the previous, it may be possible to only
 680         *   expose one of the CDP resources to pseudo-locking and
 681         *   hide the other. For example, we could consider to only
 682         *   expose L3DATA and since the L3 cache is unified it is
 683         *   still possible to place instructions there are execute it.
 684         * - If only one region is exposed to pseudo-locking we should
 685         *   still keep in mind that availability of a portion of cache
 686         *   for pseudo-locking should take into account both resources.
 687         *   Similarly, if a pseudo-locked region is created in one
 688         *   resource, the portion of cache used by it should be made
 689         *   unavailable to all future allocations from both resources.
 690         */
 691        if (rdt_resources_all[RDT_RESOURCE_L3DATA].alloc_enabled ||
 692            rdt_resources_all[RDT_RESOURCE_L2DATA].alloc_enabled) {
 693                rdt_last_cmd_puts("CDP enabled\n");
 694                return -EINVAL;
 695        }
 696
 697        /*
 698         * Not knowing the bits to disable prefetching implies that this
 699         * platform does not support Cache Pseudo-Locking.
 700         */
 701        prefetch_disable_bits = get_prefetch_disable_bits();
 702        if (prefetch_disable_bits == 0) {
 703                rdt_last_cmd_puts("Pseudo-locking not supported\n");
 704                return -EINVAL;
 705        }
 706
 707        if (rdtgroup_monitor_in_progress(rdtgrp)) {
 708                rdt_last_cmd_puts("Monitoring in progress\n");
 709                return -EINVAL;
 710        }
 711
 712        if (rdtgroup_tasks_assigned(rdtgrp)) {
 713                rdt_last_cmd_puts("Tasks assigned to resource group\n");
 714                return -EINVAL;
 715        }
 716
 717        if (!cpumask_empty(&rdtgrp->cpu_mask)) {
 718                rdt_last_cmd_puts("CPUs assigned to resource group\n");
 719                return -EINVAL;
 720        }
 721
 722        if (rdtgroup_locksetup_user_restrict(rdtgrp)) {
 723                rdt_last_cmd_puts("Unable to modify resctrl permissions\n");
 724                return -EIO;
 725        }
 726
 727        ret = pseudo_lock_init(rdtgrp);
 728        if (ret) {
 729                rdt_last_cmd_puts("Unable to init pseudo-lock region\n");
 730                goto out_release;
 731        }
 732
 733        /*
 734         * If this system is capable of monitoring a rmid would have been
 735         * allocated when the control group was created. This is not needed
 736         * anymore when this group would be used for pseudo-locking. This
 737         * is safe to call on platforms not capable of monitoring.
 738         */
 739        free_rmid(rdtgrp->mon.rmid);
 740
 741        ret = 0;
 742        goto out;
 743
 744out_release:
 745        rdtgroup_locksetup_user_restore(rdtgrp);
 746out:
 747        return ret;
 748}
 749
 750/**
 751 * rdtgroup_locksetup_exit - resource group exist locksetup mode
 752 * @rdtgrp: resource group
 753 *
 754 * When a resource group exits locksetup mode the earlier restrictions are
 755 * lifted.
 756 *
 757 * Return: 0 on success, <0 on failure
 758 */
 759int rdtgroup_locksetup_exit(struct rdtgroup *rdtgrp)
 760{
 761        int ret;
 762
 763        if (rdt_mon_capable) {
 764                ret = alloc_rmid();
 765                if (ret < 0) {
 766                        rdt_last_cmd_puts("Out of RMIDs\n");
 767                        return ret;
 768                }
 769                rdtgrp->mon.rmid = ret;
 770        }
 771
 772        ret = rdtgroup_locksetup_user_restore(rdtgrp);
 773        if (ret) {
 774                free_rmid(rdtgrp->mon.rmid);
 775                return ret;
 776        }
 777
 778        pseudo_lock_free(rdtgrp);
 779        return 0;
 780}
 781
 782/**
 783 * rdtgroup_cbm_overlaps_pseudo_locked - Test if CBM or portion is pseudo-locked
 784 * @d: RDT domain
 785 * @cbm: CBM to test
 786 *
 787 * @d represents a cache instance and @cbm a capacity bitmask that is
 788 * considered for it. Determine if @cbm overlaps with any existing
 789 * pseudo-locked region on @d.
 790 *
 791 * @cbm is unsigned long, even if only 32 bits are used, to make the
 792 * bitmap functions work correctly.
 793 *
 794 * Return: true if @cbm overlaps with pseudo-locked region on @d, false
 795 * otherwise.
 796 */
 797bool rdtgroup_cbm_overlaps_pseudo_locked(struct rdt_domain *d, unsigned long cbm)
 798{
 799        unsigned int cbm_len;
 800        unsigned long cbm_b;
 801
 802        if (d->plr) {
 803                cbm_len = d->plr->r->cache.cbm_len;
 804                cbm_b = d->plr->cbm;
 805                if (bitmap_intersects(&cbm, &cbm_b, cbm_len))
 806                        return true;
 807        }
 808        return false;
 809}
 810
 811/**
 812 * rdtgroup_pseudo_locked_in_hierarchy - Pseudo-locked region in cache hierarchy
 813 * @d: RDT domain under test
 814 *
 815 * The setup of a pseudo-locked region affects all cache instances within
 816 * the hierarchy of the region. It is thus essential to know if any
 817 * pseudo-locked regions exist within a cache hierarchy to prevent any
 818 * attempts to create new pseudo-locked regions in the same hierarchy.
 819 *
 820 * Return: true if a pseudo-locked region exists in the hierarchy of @d or
 821 *         if it is not possible to test due to memory allocation issue,
 822 *         false otherwise.
 823 */
 824bool rdtgroup_pseudo_locked_in_hierarchy(struct rdt_domain *d)
 825{
 826        cpumask_var_t cpu_with_psl;
 827        struct rdt_resource *r;
 828        struct rdt_domain *d_i;
 829        bool ret = false;
 830
 831        if (!zalloc_cpumask_var(&cpu_with_psl, GFP_KERNEL))
 832                return true;
 833
 834        /*
 835         * First determine which cpus have pseudo-locked regions
 836         * associated with them.
 837         */
 838        for_each_alloc_enabled_rdt_resource(r) {
 839                list_for_each_entry(d_i, &r->domains, list) {
 840                        if (d_i->plr)
 841                                cpumask_or(cpu_with_psl, cpu_with_psl,
 842                                           &d_i->cpu_mask);
 843                }
 844        }
 845
 846        /*
 847         * Next test if new pseudo-locked region would intersect with
 848         * existing region.
 849         */
 850        if (cpumask_intersects(&d->cpu_mask, cpu_with_psl))
 851                ret = true;
 852
 853        free_cpumask_var(cpu_with_psl);
 854        return ret;
 855}
 856
 857/**
 858 * measure_cycles_lat_fn - Measure cycle latency to read pseudo-locked memory
 859 * @_plr: pseudo-lock region to measure
 860 *
 861 * There is no deterministic way to test if a memory region is cached. One
 862 * way is to measure how long it takes to read the memory, the speed of
 863 * access is a good way to learn how close to the cpu the data was. Even
 864 * more, if the prefetcher is disabled and the memory is read at a stride
 865 * of half the cache line, then a cache miss will be easy to spot since the
 866 * read of the first half would be significantly slower than the read of
 867 * the second half.
 868 *
 869 * Return: 0. Waiter on waitqueue will be woken on completion.
 870 */
 871static int measure_cycles_lat_fn(void *_plr)
 872{
 873        struct pseudo_lock_region *plr = _plr;
 874        unsigned long i;
 875        u64 start, end;
 876        void *mem_r;
 877
 878        local_irq_disable();
 879        /*
 880         * Disable hardware prefetchers.
 881         */
 882        wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
 883        mem_r = READ_ONCE(plr->kmem);
 884        /*
 885         * Dummy execute of the time measurement to load the needed
 886         * instructions into the L1 instruction cache.
 887         */
 888        start = rdtsc_ordered();
 889        for (i = 0; i < plr->size; i += 32) {
 890                start = rdtsc_ordered();
 891                asm volatile("mov (%0,%1,1), %%eax\n\t"
 892                             :
 893                             : "r" (mem_r), "r" (i)
 894                             : "%eax", "memory");
 895                end = rdtsc_ordered();
 896                trace_pseudo_lock_mem_latency((u32)(end - start));
 897        }
 898        wrmsr(MSR_MISC_FEATURE_CONTROL, 0x0, 0x0);
 899        local_irq_enable();
 900        plr->thread_done = 1;
 901        wake_up_interruptible(&plr->lock_thread_wq);
 902        return 0;
 903}
 904
 905/*
 906 * Create a perf_event_attr for the hit and miss perf events that will
 907 * be used during the performance measurement. A perf_event maintains
 908 * a pointer to its perf_event_attr so a unique attribute structure is
 909 * created for each perf_event.
 910 *
 911 * The actual configuration of the event is set right before use in order
 912 * to use the X86_CONFIG macro.
 913 */
 914static struct perf_event_attr perf_miss_attr = {
 915        .type           = PERF_TYPE_RAW,
 916        .size           = sizeof(struct perf_event_attr),
 917        .pinned         = 1,
 918        .disabled       = 0,
 919        .exclude_user   = 1,
 920};
 921
 922static struct perf_event_attr perf_hit_attr = {
 923        .type           = PERF_TYPE_RAW,
 924        .size           = sizeof(struct perf_event_attr),
 925        .pinned         = 1,
 926        .disabled       = 0,
 927        .exclude_user   = 1,
 928};
 929
 930struct residency_counts {
 931        u64 miss_before, hits_before;
 932        u64 miss_after,  hits_after;
 933};
 934
 935static int measure_residency_fn(struct perf_event_attr *miss_attr,
 936                                struct perf_event_attr *hit_attr,
 937                                struct pseudo_lock_region *plr,
 938                                struct residency_counts *counts)
 939{
 940        u64 hits_before = 0, hits_after = 0, miss_before = 0, miss_after = 0;
 941        struct perf_event *miss_event, *hit_event;
 942        int hit_pmcnum, miss_pmcnum;
 943        unsigned int line_size;
 944        unsigned int size;
 945        unsigned long i;
 946        void *mem_r;
 947        u64 tmp;
 948
 949        miss_event = perf_event_create_kernel_counter(miss_attr, plr->cpu,
 950                                                      NULL, NULL, NULL);
 951        if (IS_ERR(miss_event))
 952                goto out;
 953
 954        hit_event = perf_event_create_kernel_counter(hit_attr, plr->cpu,
 955                                                     NULL, NULL, NULL);
 956        if (IS_ERR(hit_event))
 957                goto out_miss;
 958
 959        local_irq_disable();
 960        /*
 961         * Check any possible error state of events used by performing
 962         * one local read.
 963         */
 964        if (perf_event_read_local(miss_event, &tmp, NULL, NULL)) {
 965                local_irq_enable();
 966                goto out_hit;
 967        }
 968        if (perf_event_read_local(hit_event, &tmp, NULL, NULL)) {
 969                local_irq_enable();
 970                goto out_hit;
 971        }
 972
 973        /*
 974         * Disable hardware prefetchers.
 975         */
 976        wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
 977
 978        /* Initialize rest of local variables */
 979        /*
 980         * Performance event has been validated right before this with
 981         * interrupts disabled - it is thus safe to read the counter index.
 982         */
 983        miss_pmcnum = x86_perf_rdpmc_index(miss_event);
 984        hit_pmcnum = x86_perf_rdpmc_index(hit_event);
 985        line_size = READ_ONCE(plr->line_size);
 986        mem_r = READ_ONCE(plr->kmem);
 987        size = READ_ONCE(plr->size);
 988
 989        /*
 990         * Read counter variables twice - first to load the instructions
 991         * used in L1 cache, second to capture accurate value that does not
 992         * include cache misses incurred because of instruction loads.
 993         */
 994        rdpmcl(hit_pmcnum, hits_before);
 995        rdpmcl(miss_pmcnum, miss_before);
 996        /*
 997         * From SDM: Performing back-to-back fast reads are not guaranteed
 998         * to be monotonic.
 999         * Use LFENCE to ensure all previous instructions are retired
1000         * before proceeding.
1001         */
1002        rmb();
1003        rdpmcl(hit_pmcnum, hits_before);
1004        rdpmcl(miss_pmcnum, miss_before);
1005        /*
1006         * Use LFENCE to ensure all previous instructions are retired
1007         * before proceeding.
1008         */
1009        rmb();
1010        for (i = 0; i < size; i += line_size) {
1011                /*
1012                 * Add a barrier to prevent speculative execution of this
1013                 * loop reading beyond the end of the buffer.
1014                 */
1015                rmb();
1016                asm volatile("mov (%0,%1,1), %%eax\n\t"
1017                             :
1018                             : "r" (mem_r), "r" (i)
1019                             : "%eax", "memory");
1020        }
1021        /*
1022         * Use LFENCE to ensure all previous instructions are retired
1023         * before proceeding.
1024         */
1025        rmb();
1026        rdpmcl(hit_pmcnum, hits_after);
1027        rdpmcl(miss_pmcnum, miss_after);
1028        /*
1029         * Use LFENCE to ensure all previous instructions are retired
1030         * before proceeding.
1031         */
1032        rmb();
1033        /* Re-enable hardware prefetchers */
1034        wrmsr(MSR_MISC_FEATURE_CONTROL, 0x0, 0x0);
1035        local_irq_enable();
1036out_hit:
1037        perf_event_release_kernel(hit_event);
1038out_miss:
1039        perf_event_release_kernel(miss_event);
1040out:
1041        /*
1042         * All counts will be zero on failure.
1043         */
1044        counts->miss_before = miss_before;
1045        counts->hits_before = hits_before;
1046        counts->miss_after  = miss_after;
1047        counts->hits_after  = hits_after;
1048        return 0;
1049}
1050
1051static int measure_l2_residency(void *_plr)
1052{
1053        struct pseudo_lock_region *plr = _plr;
1054        struct residency_counts counts = {0};
1055
1056        /*
1057         * Non-architectural event for the Goldmont Microarchitecture
1058         * from Intel x86 Architecture Software Developer Manual (SDM):
1059         * MEM_LOAD_UOPS_RETIRED D1H (event number)
1060         * Umask values:
1061         *     L2_HIT   02H
1062         *     L2_MISS  10H
1063         */
1064        switch (boot_cpu_data.x86_model) {
1065        case INTEL_FAM6_ATOM_GOLDMONT:
1066        case INTEL_FAM6_ATOM_GOLDMONT_PLUS:
1067                perf_miss_attr.config = X86_CONFIG(.event = 0xd1,
1068                                                   .umask = 0x10);
1069                perf_hit_attr.config = X86_CONFIG(.event = 0xd1,
1070                                                  .umask = 0x2);
1071                break;
1072        default:
1073                goto out;
1074        }
1075
1076        measure_residency_fn(&perf_miss_attr, &perf_hit_attr, plr, &counts);
1077        /*
1078         * If a failure prevented the measurements from succeeding
1079         * tracepoints will still be written and all counts will be zero.
1080         */
1081        trace_pseudo_lock_l2(counts.hits_after - counts.hits_before,
1082                             counts.miss_after - counts.miss_before);
1083out:
1084        plr->thread_done = 1;
1085        wake_up_interruptible(&plr->lock_thread_wq);
1086        return 0;
1087}
1088
1089static int measure_l3_residency(void *_plr)
1090{
1091        struct pseudo_lock_region *plr = _plr;
1092        struct residency_counts counts = {0};
1093
1094        /*
1095         * On Broadwell Microarchitecture the MEM_LOAD_UOPS_RETIRED event
1096         * has two "no fix" errata associated with it: BDM35 and BDM100. On
1097         * this platform the following events are used instead:
1098         * LONGEST_LAT_CACHE 2EH (Documented in SDM)
1099         *       REFERENCE 4FH
1100         *       MISS      41H
1101         */
1102
1103        switch (boot_cpu_data.x86_model) {
1104        case INTEL_FAM6_BROADWELL_X:
1105                /* On BDW the hit event counts references, not hits */
1106                perf_hit_attr.config = X86_CONFIG(.event = 0x2e,
1107                                                  .umask = 0x4f);
1108                perf_miss_attr.config = X86_CONFIG(.event = 0x2e,
1109                                                   .umask = 0x41);
1110                break;
1111        default:
1112                goto out;
1113        }
1114
1115        measure_residency_fn(&perf_miss_attr, &perf_hit_attr, plr, &counts);
1116        /*
1117         * If a failure prevented the measurements from succeeding
1118         * tracepoints will still be written and all counts will be zero.
1119         */
1120
1121        counts.miss_after -= counts.miss_before;
1122        if (boot_cpu_data.x86_model == INTEL_FAM6_BROADWELL_X) {
1123                /*
1124                 * On BDW references and misses are counted, need to adjust.
1125                 * Sometimes the "hits" counter is a bit more than the
1126                 * references, for example, x references but x + 1 hits.
1127                 * To not report invalid hit values in this case we treat
1128                 * that as misses equal to references.
1129                 */
1130                /* First compute the number of cache references measured */
1131                counts.hits_after -= counts.hits_before;
1132                /* Next convert references to cache hits */
1133                counts.hits_after -= min(counts.miss_after, counts.hits_after);
1134        } else {
1135                counts.hits_after -= counts.hits_before;
1136        }
1137
1138        trace_pseudo_lock_l3(counts.hits_after, counts.miss_after);
1139out:
1140        plr->thread_done = 1;
1141        wake_up_interruptible(&plr->lock_thread_wq);
1142        return 0;
1143}
1144
1145/**
1146 * pseudo_lock_measure_cycles - Trigger latency measure to pseudo-locked region
1147 * @rdtgrp: Resource group to which the pseudo-locked region belongs.
1148 * @sel: Selector of which measurement to perform on a pseudo-locked region.
1149 *
1150 * The measurement of latency to access a pseudo-locked region should be
1151 * done from a cpu that is associated with that pseudo-locked region.
1152 * Determine which cpu is associated with this region and start a thread on
1153 * that cpu to perform the measurement, wait for that thread to complete.
1154 *
1155 * Return: 0 on success, <0 on failure
1156 */
1157static int pseudo_lock_measure_cycles(struct rdtgroup *rdtgrp, int sel)
1158{
1159        struct pseudo_lock_region *plr = rdtgrp->plr;
1160        struct task_struct *thread;
1161        unsigned int cpu;
1162        int ret = -1;
1163
1164        cpus_read_lock();
1165        mutex_lock(&rdtgroup_mutex);
1166
1167        if (rdtgrp->flags & RDT_DELETED) {
1168                ret = -ENODEV;
1169                goto out;
1170        }
1171
1172        if (!plr->d) {
1173                ret = -ENODEV;
1174                goto out;
1175        }
1176
1177        plr->thread_done = 0;
1178        cpu = cpumask_first(&plr->d->cpu_mask);
1179        if (!cpu_online(cpu)) {
1180                ret = -ENODEV;
1181                goto out;
1182        }
1183
1184        plr->cpu = cpu;
1185
1186        if (sel == 1)
1187                thread = kthread_create_on_node(measure_cycles_lat_fn, plr,
1188                                                cpu_to_node(cpu),
1189                                                "pseudo_lock_measure/%u",
1190                                                cpu);
1191        else if (sel == 2)
1192                thread = kthread_create_on_node(measure_l2_residency, plr,
1193                                                cpu_to_node(cpu),
1194                                                "pseudo_lock_measure/%u",
1195                                                cpu);
1196        else if (sel == 3)
1197                thread = kthread_create_on_node(measure_l3_residency, plr,
1198                                                cpu_to_node(cpu),
1199                                                "pseudo_lock_measure/%u",
1200                                                cpu);
1201        else
1202                goto out;
1203
1204        if (IS_ERR(thread)) {
1205                ret = PTR_ERR(thread);
1206                goto out;
1207        }
1208        kthread_bind(thread, cpu);
1209        wake_up_process(thread);
1210
1211        ret = wait_event_interruptible(plr->lock_thread_wq,
1212                                       plr->thread_done == 1);
1213        if (ret < 0)
1214                goto out;
1215
1216        ret = 0;
1217
1218out:
1219        mutex_unlock(&rdtgroup_mutex);
1220        cpus_read_unlock();
1221        return ret;
1222}
1223
1224static ssize_t pseudo_lock_measure_trigger(struct file *file,
1225                                           const char __user *user_buf,
1226                                           size_t count, loff_t *ppos)
1227{
1228        struct rdtgroup *rdtgrp = file->private_data;
1229        size_t buf_size;
1230        char buf[32];
1231        int ret;
1232        int sel;
1233
1234        buf_size = min(count, (sizeof(buf) - 1));
1235        if (copy_from_user(buf, user_buf, buf_size))
1236                return -EFAULT;
1237
1238        buf[buf_size] = '\0';
1239        ret = kstrtoint(buf, 10, &sel);
1240        if (ret == 0) {
1241                if (sel != 1 && sel != 2 && sel != 3)
1242                        return -EINVAL;
1243                ret = debugfs_file_get(file->f_path.dentry);
1244                if (ret)
1245                        return ret;
1246                ret = pseudo_lock_measure_cycles(rdtgrp, sel);
1247                if (ret == 0)
1248                        ret = count;
1249                debugfs_file_put(file->f_path.dentry);
1250        }
1251
1252        return ret;
1253}
1254
1255static const struct file_operations pseudo_measure_fops = {
1256        .write = pseudo_lock_measure_trigger,
1257        .open = simple_open,
1258        .llseek = default_llseek,
1259};
1260
1261/**
1262 * rdtgroup_pseudo_lock_create - Create a pseudo-locked region
1263 * @rdtgrp: resource group to which pseudo-lock region belongs
1264 *
1265 * Called when a resource group in the pseudo-locksetup mode receives a
1266 * valid schemata that should be pseudo-locked. Since the resource group is
1267 * in pseudo-locksetup mode the &struct pseudo_lock_region has already been
1268 * allocated and initialized with the essential information. If a failure
1269 * occurs the resource group remains in the pseudo-locksetup mode with the
1270 * &struct pseudo_lock_region associated with it, but cleared from all
1271 * information and ready for the user to re-attempt pseudo-locking by
1272 * writing the schemata again.
1273 *
1274 * Return: 0 if the pseudo-locked region was successfully pseudo-locked, <0
1275 * on failure. Descriptive error will be written to last_cmd_status buffer.
1276 */
1277int rdtgroup_pseudo_lock_create(struct rdtgroup *rdtgrp)
1278{
1279        struct pseudo_lock_region *plr = rdtgrp->plr;
1280        struct task_struct *thread;
1281        unsigned int new_minor;
1282        struct device *dev;
1283        int ret;
1284
1285        ret = pseudo_lock_region_alloc(plr);
1286        if (ret < 0)
1287                return ret;
1288
1289        ret = pseudo_lock_cstates_constrain(plr);
1290        if (ret < 0) {
1291                ret = -EINVAL;
1292                goto out_region;
1293        }
1294
1295        plr->thread_done = 0;
1296
1297        thread = kthread_create_on_node(pseudo_lock_fn, rdtgrp,
1298                                        cpu_to_node(plr->cpu),
1299                                        "pseudo_lock/%u", plr->cpu);
1300        if (IS_ERR(thread)) {
1301                ret = PTR_ERR(thread);
1302                rdt_last_cmd_printf("Locking thread returned error %d\n", ret);
1303                goto out_cstates;
1304        }
1305
1306        kthread_bind(thread, plr->cpu);
1307        wake_up_process(thread);
1308
1309        ret = wait_event_interruptible(plr->lock_thread_wq,
1310                                       plr->thread_done == 1);
1311        if (ret < 0) {
1312                /*
1313                 * If the thread does not get on the CPU for whatever
1314                 * reason and the process which sets up the region is
1315                 * interrupted then this will leave the thread in runnable
1316                 * state and once it gets on the CPU it will dereference
1317                 * the cleared, but not freed, plr struct resulting in an
1318                 * empty pseudo-locking loop.
1319                 */
1320                rdt_last_cmd_puts("Locking thread interrupted\n");
1321                goto out_cstates;
1322        }
1323
1324        ret = pseudo_lock_minor_get(&new_minor);
1325        if (ret < 0) {
1326                rdt_last_cmd_puts("Unable to obtain a new minor number\n");
1327                goto out_cstates;
1328        }
1329
1330        /*
1331         * Unlock access but do not release the reference. The
1332         * pseudo-locked region will still be here on return.
1333         *
1334         * The mutex has to be released temporarily to avoid a potential
1335         * deadlock with the mm->mmap_lock which is obtained in the
1336         * device_create() and debugfs_create_dir() callpath below as well as
1337         * before the mmap() callback is called.
1338         */
1339        mutex_unlock(&rdtgroup_mutex);
1340
1341        if (!IS_ERR_OR_NULL(debugfs_resctrl)) {
1342                plr->debugfs_dir = debugfs_create_dir(rdtgrp->kn->name,
1343                                                      debugfs_resctrl);
1344                if (!IS_ERR_OR_NULL(plr->debugfs_dir))
1345                        debugfs_create_file("pseudo_lock_measure", 0200,
1346                                            plr->debugfs_dir, rdtgrp,
1347                                            &pseudo_measure_fops);
1348        }
1349
1350        dev = device_create(pseudo_lock_class, NULL,
1351                            MKDEV(pseudo_lock_major, new_minor),
1352                            rdtgrp, "%s", rdtgrp->kn->name);
1353
1354        mutex_lock(&rdtgroup_mutex);
1355
1356        if (IS_ERR(dev)) {
1357                ret = PTR_ERR(dev);
1358                rdt_last_cmd_printf("Failed to create character device: %d\n",
1359                                    ret);
1360                goto out_debugfs;
1361        }
1362
1363        /* We released the mutex - check if group was removed while we did so */
1364        if (rdtgrp->flags & RDT_DELETED) {
1365                ret = -ENODEV;
1366                goto out_device;
1367        }
1368
1369        plr->minor = new_minor;
1370
1371        rdtgrp->mode = RDT_MODE_PSEUDO_LOCKED;
1372        closid_free(rdtgrp->closid);
1373        rdtgroup_kn_mode_restore(rdtgrp, "cpus", 0444);
1374        rdtgroup_kn_mode_restore(rdtgrp, "cpus_list", 0444);
1375
1376        ret = 0;
1377        goto out;
1378
1379out_device:
1380        device_destroy(pseudo_lock_class, MKDEV(pseudo_lock_major, new_minor));
1381out_debugfs:
1382        debugfs_remove_recursive(plr->debugfs_dir);
1383        pseudo_lock_minor_release(new_minor);
1384out_cstates:
1385        pseudo_lock_cstates_relax(plr);
1386out_region:
1387        pseudo_lock_region_clear(plr);
1388out:
1389        return ret;
1390}
1391
1392/**
1393 * rdtgroup_pseudo_lock_remove - Remove a pseudo-locked region
1394 * @rdtgrp: resource group to which the pseudo-locked region belongs
1395 *
1396 * The removal of a pseudo-locked region can be initiated when the resource
1397 * group is removed from user space via a "rmdir" from userspace or the
1398 * unmount of the resctrl filesystem. On removal the resource group does
1399 * not go back to pseudo-locksetup mode before it is removed, instead it is
1400 * removed directly. There is thus asymmetry with the creation where the
1401 * &struct pseudo_lock_region is removed here while it was not created in
1402 * rdtgroup_pseudo_lock_create().
1403 *
1404 * Return: void
1405 */
1406void rdtgroup_pseudo_lock_remove(struct rdtgroup *rdtgrp)
1407{
1408        struct pseudo_lock_region *plr = rdtgrp->plr;
1409
1410        if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
1411                /*
1412                 * Default group cannot be a pseudo-locked region so we can
1413                 * free closid here.
1414                 */
1415                closid_free(rdtgrp->closid);
1416                goto free;
1417        }
1418
1419        pseudo_lock_cstates_relax(plr);
1420        debugfs_remove_recursive(rdtgrp->plr->debugfs_dir);
1421        device_destroy(pseudo_lock_class, MKDEV(pseudo_lock_major, plr->minor));
1422        pseudo_lock_minor_release(plr->minor);
1423
1424free:
1425        pseudo_lock_free(rdtgrp);
1426}
1427
1428static int pseudo_lock_dev_open(struct inode *inode, struct file *filp)
1429{
1430        struct rdtgroup *rdtgrp;
1431
1432        mutex_lock(&rdtgroup_mutex);
1433
1434        rdtgrp = region_find_by_minor(iminor(inode));
1435        if (!rdtgrp) {
1436                mutex_unlock(&rdtgroup_mutex);
1437                return -ENODEV;
1438        }
1439
1440        filp->private_data = rdtgrp;
1441        atomic_inc(&rdtgrp->waitcount);
1442        /* Perform a non-seekable open - llseek is not supported */
1443        filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1444
1445        mutex_unlock(&rdtgroup_mutex);
1446
1447        return 0;
1448}
1449
1450static int pseudo_lock_dev_release(struct inode *inode, struct file *filp)
1451{
1452        struct rdtgroup *rdtgrp;
1453
1454        mutex_lock(&rdtgroup_mutex);
1455        rdtgrp = filp->private_data;
1456        WARN_ON(!rdtgrp);
1457        if (!rdtgrp) {
1458                mutex_unlock(&rdtgroup_mutex);
1459                return -ENODEV;
1460        }
1461        filp->private_data = NULL;
1462        atomic_dec(&rdtgrp->waitcount);
1463        mutex_unlock(&rdtgroup_mutex);
1464        return 0;
1465}
1466
1467static int pseudo_lock_dev_mremap(struct vm_area_struct *area)
1468{
1469        /* Not supported */
1470        return -EINVAL;
1471}
1472
1473static const struct vm_operations_struct pseudo_mmap_ops = {
1474        .mremap = pseudo_lock_dev_mremap,
1475};
1476
1477static int pseudo_lock_dev_mmap(struct file *filp, struct vm_area_struct *vma)
1478{
1479        unsigned long vsize = vma->vm_end - vma->vm_start;
1480        unsigned long off = vma->vm_pgoff << PAGE_SHIFT;
1481        struct pseudo_lock_region *plr;
1482        struct rdtgroup *rdtgrp;
1483        unsigned long physical;
1484        unsigned long psize;
1485
1486        mutex_lock(&rdtgroup_mutex);
1487
1488        rdtgrp = filp->private_data;
1489        WARN_ON(!rdtgrp);
1490        if (!rdtgrp) {
1491                mutex_unlock(&rdtgroup_mutex);
1492                return -ENODEV;
1493        }
1494
1495        plr = rdtgrp->plr;
1496
1497        if (!plr->d) {
1498                mutex_unlock(&rdtgroup_mutex);
1499                return -ENODEV;
1500        }
1501
1502        /*
1503         * Task is required to run with affinity to the cpus associated
1504         * with the pseudo-locked region. If this is not the case the task
1505         * may be scheduled elsewhere and invalidate entries in the
1506         * pseudo-locked region.
1507         */
1508        if (!cpumask_subset(current->cpus_ptr, &plr->d->cpu_mask)) {
1509                mutex_unlock(&rdtgroup_mutex);
1510                return -EINVAL;
1511        }
1512
1513        physical = __pa(plr->kmem) >> PAGE_SHIFT;
1514        psize = plr->size - off;
1515
1516        if (off > plr->size) {
1517                mutex_unlock(&rdtgroup_mutex);
1518                return -ENOSPC;
1519        }
1520
1521        /*
1522         * Ensure changes are carried directly to the memory being mapped,
1523         * do not allow copy-on-write mapping.
1524         */
1525        if (!(vma->vm_flags & VM_SHARED)) {
1526                mutex_unlock(&rdtgroup_mutex);
1527                return -EINVAL;
1528        }
1529
1530        if (vsize > psize) {
1531                mutex_unlock(&rdtgroup_mutex);
1532                return -ENOSPC;
1533        }
1534
1535        memset(plr->kmem + off, 0, vsize);
1536
1537        if (remap_pfn_range(vma, vma->vm_start, physical + vma->vm_pgoff,
1538                            vsize, vma->vm_page_prot)) {
1539                mutex_unlock(&rdtgroup_mutex);
1540                return -EAGAIN;
1541        }
1542        vma->vm_ops = &pseudo_mmap_ops;
1543        mutex_unlock(&rdtgroup_mutex);
1544        return 0;
1545}
1546
1547static const struct file_operations pseudo_lock_dev_fops = {
1548        .owner =        THIS_MODULE,
1549        .llseek =       no_llseek,
1550        .read =         NULL,
1551        .write =        NULL,
1552        .open =         pseudo_lock_dev_open,
1553        .release =      pseudo_lock_dev_release,
1554        .mmap =         pseudo_lock_dev_mmap,
1555};
1556
1557static char *pseudo_lock_devnode(struct device *dev, umode_t *mode)
1558{
1559        struct rdtgroup *rdtgrp;
1560
1561        rdtgrp = dev_get_drvdata(dev);
1562        if (mode)
1563                *mode = 0600;
1564        return kasprintf(GFP_KERNEL, "pseudo_lock/%s", rdtgrp->kn->name);
1565}
1566
1567int rdt_pseudo_lock_init(void)
1568{
1569        int ret;
1570
1571        ret = register_chrdev(0, "pseudo_lock", &pseudo_lock_dev_fops);
1572        if (ret < 0)
1573                return ret;
1574
1575        pseudo_lock_major = ret;
1576
1577        pseudo_lock_class = class_create(THIS_MODULE, "pseudo_lock");
1578        if (IS_ERR(pseudo_lock_class)) {
1579                ret = PTR_ERR(pseudo_lock_class);
1580                unregister_chrdev(pseudo_lock_major, "pseudo_lock");
1581                return ret;
1582        }
1583
1584        pseudo_lock_class->devnode = pseudo_lock_devnode;
1585        return 0;
1586}
1587
1588void rdt_pseudo_lock_release(void)
1589{
1590        class_destroy(pseudo_lock_class);
1591        pseudo_lock_class = NULL;
1592        unregister_chrdev(pseudo_lock_major, "pseudo_lock");
1593        pseudo_lock_major = 0;
1594}
1595