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  */
40 static u64 prefetch_disable_bits;
41 
42 /*
43  * Major number assigned to and shared by all devices exposing
44  * pseudo-locked regions.
45  */
46 static unsigned int pseudo_lock_major;
47 static unsigned long pseudo_lock_minor_avail = GENMASK(MINORBITS, 0);
48 static 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  */
71 static 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  */
114 static 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  */
133 static 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  */
152 static 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  */
170 struct pseudo_lock_pm_req {
171 	struct list_head list;
172 	struct dev_pm_qos_request req;
173 };
174 
175 static 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  */
204 static 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 
233 out_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  */
247 static 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  */
279 static 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");
308 out_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  */
324 static 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  */
348 static 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;
375 out_region:
376 	pseudo_lock_region_clear(plr);
377 out:
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  */
391 static 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  */
417 static 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  */
532 static 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  */
552 static 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 
577 err_cpus_list:
578 	rdtgroup_kn_mode_restore(rdtgrp, "cpus_list", 0777);
579 err_cpus:
580 	rdtgroup_kn_mode_restore(rdtgrp, "cpus", 0777);
581 err_tasks:
582 	rdtgroup_kn_mode_restore(rdtgrp, "tasks", 0777);
583 out:
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  */
599 static 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 
624 err_cpus_list:
625 	rdtgroup_kn_mode_restrict(rdtgrp, "cpus_list");
626 err_cpus:
627 	rdtgroup_kn_mode_restrict(rdtgrp, "cpus");
628 err_tasks:
629 	rdtgroup_kn_mode_restrict(rdtgrp, "tasks");
630 out:
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  */
652 int 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 
744 out_release:
745 	rdtgroup_locksetup_user_restore(rdtgrp);
746 out:
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  */
759 int 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  */
797 bool 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  */
824 bool 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  */
871 static 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  */
914 static 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 
922 static 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 
930 struct residency_counts {
931 	u64 miss_before, hits_before;
932 	u64 miss_after,  hits_after;
933 };
934 
935 static 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();
1036 out_hit:
1037 	perf_event_release_kernel(hit_event);
1038 out_miss:
1039 	perf_event_release_kernel(miss_event);
1040 out:
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 
1051 static 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);
1083 out:
1084 	plr->thread_done = 1;
1085 	wake_up_interruptible(&plr->lock_thread_wq);
1086 	return 0;
1087 }
1088 
1089 static 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);
1139 out:
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  */
1157 static 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 
1218 out:
1219 	mutex_unlock(&rdtgroup_mutex);
1220 	cpus_read_unlock();
1221 	return ret;
1222 }
1223 
1224 static 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 
1255 static 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  */
1277 int 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 
1379 out_device:
1380 	device_destroy(pseudo_lock_class, MKDEV(pseudo_lock_major, new_minor));
1381 out_debugfs:
1382 	debugfs_remove_recursive(plr->debugfs_dir);
1383 	pseudo_lock_minor_release(new_minor);
1384 out_cstates:
1385 	pseudo_lock_cstates_relax(plr);
1386 out_region:
1387 	pseudo_lock_region_clear(plr);
1388 out:
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  */
1406 void 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 
1424 free:
1425 	pseudo_lock_free(rdtgrp);
1426 }
1427 
1428 static 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 
1450 static 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 
1467 static int pseudo_lock_dev_mremap(struct vm_area_struct *area)
1468 {
1469 	/* Not supported */
1470 	return -EINVAL;
1471 }
1472 
1473 static const struct vm_operations_struct pseudo_mmap_ops = {
1474 	.mremap = pseudo_lock_dev_mremap,
1475 };
1476 
1477 static 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 
1547 static 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 
1557 static 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 
1567 int 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 
1588 void 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