uffd-stress.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Stress userfaultfd syscall.
  4 *
  5 *  Copyright (C) 2015  Red Hat, Inc.
  6 *
  7 * This test allocates two virtual areas and bounces the physical
  8 * memory across the two virtual areas (from area_src to area_dst)
  9 * using userfaultfd.
 10 *
 11 * There are three threads running per CPU:
 12 *
 13 * 1) one per-CPU thread takes a per-page pthread_mutex in a random
 14 *    page of the area_dst (while the physical page may still be in
 15 *    area_src), and increments a per-page counter in the same page,
 16 *    and checks its value against a verification region.
 17 *
 18 * 2) another per-CPU thread handles the userfaults generated by
 19 *    thread 1 above. userfaultfd blocking reads or poll() modes are
 20 *    exercised interleaved.
 21 *
 22 * 3) one last per-CPU thread transfers the memory in the background
 23 *    at maximum bandwidth (if not already transferred by thread
 24 *    2). Each cpu thread takes cares of transferring a portion of the
 25 *    area.
 26 *
 27 * When all threads of type 3 completed the transfer, one bounce is
 28 * complete. area_src and area_dst are then swapped. All threads are
 29 * respawned and so the bounce is immediately restarted in the
 30 * opposite direction.
 31 *
 32 * per-CPU threads 1 by triggering userfaults inside
 33 * pthread_mutex_lock will also verify the atomicity of the memory
 34 * transfer (UFFDIO_COPY).
 35 */
 36
 37#include "uffd-common.h"
 38
 39uint64_t features;
 40#ifdef __NR_userfaultfd
 41
 42#define BOUNCE_RANDOM		(1<<0)
 43#define BOUNCE_RACINGFAULTS	(1<<1)
 44#define BOUNCE_VERIFY		(1<<2)
 45#define BOUNCE_POLL		(1<<3)
 46static int bounces;
 47/* defined globally for this particular test as the sigalrm handler
 48 * depends on test_uffdio_*_eexist.
 49 * XXX: define gopts in main() when we figure out a way to deal with
 50 * test_uffdio_*_eexist.
 51 */
 52static uffd_global_test_opts_t *gopts;
 53
 54/* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
 55#define ALARM_INTERVAL_SECS 10
 56static char *zeropage;
 57pthread_attr_t attr;
 58
 59#define swap(a, b) \
 60	do { __auto_type __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
 61
 62const char *examples =
 63	"# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
 64	"./uffd-stress anon 100 99999\n\n"
 65	"# Run share memory test on 1GiB region with 99 bounces:\n"
 66	"./uffd-stress shmem 1000 99\n\n"
 67	"# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
 68	"./uffd-stress hugetlb 256 50\n\n"
 69	"# Run the same hugetlb test but using private file:\n"
 70	"./uffd-stress hugetlb-private 256 50\n\n"
 71	"# 10MiB-~6GiB 999 bounces anonymous test, "
 72	"continue forever unless an error triggers\n"
 73	"while ./uffd-stress anon $[RANDOM % 6000 + 10] 999; do true; done\n\n";
 74
 75static void usage(void)
 76{
 77	fprintf(stderr, "\nUsage: ./uffd-stress <test type> <MiB> <bounces>\n\n");
 78	fprintf(stderr, "Supported <test type>: anon, hugetlb, "
 79		"hugetlb-private, shmem, shmem-private\n\n");
 80	fprintf(stderr, "Examples:\n\n");
 81	fprintf(stderr, "%s", examples);
 82	exit(1);
 83}
 84
 85static void uffd_stats_reset(uffd_global_test_opts_t *gopts, struct uffd_args *args,
 86			     unsigned long n_cpus)
 87{
 88	int i;
 89
 90	for (i = 0; i < n_cpus; i++) {
 91		args[i].cpu = i;
 92		args[i].apply_wp = gopts->test_uffdio_wp;
 93		args[i].missing_faults = 0;
 94		args[i].wp_faults = 0;
 95		args[i].minor_faults = 0;
 96		args[i].gopts = gopts;
 97	}
 98}
 99
100static void *locking_thread(void *arg)
101{
102	struct uffd_args *args = (struct uffd_args *) arg;
103	uffd_global_test_opts_t *gopts = args->gopts;
104	unsigned long cpu = (unsigned long) args->cpu;
105	unsigned long page_nr;
106	unsigned long long count;
107
108	if (!(bounces & BOUNCE_RANDOM)) {
109		page_nr = -bounces;
110		if (!(bounces & BOUNCE_RACINGFAULTS))
111			page_nr += cpu * gopts->nr_pages_per_cpu;
112	}
113
114	while (!gopts->finished) {
115		if (bounces & BOUNCE_RANDOM) {
116			if (getrandom(&page_nr, sizeof(page_nr), 0) != sizeof(page_nr))
117				err("getrandom failed");
118		} else
119			page_nr += 1;
120		page_nr %= gopts->nr_pages;
121		pthread_mutex_lock(area_mutex(gopts->area_dst, page_nr, gopts));
122		count = *area_count(gopts->area_dst, page_nr, gopts);
123		if (count != gopts->count_verify[page_nr])
124			err("page_nr %lu memory corruption %llu %llu",
125			    page_nr, count, gopts->count_verify[page_nr]);
126		count++;
127		*area_count(gopts->area_dst, page_nr, gopts) = gopts->count_verify[page_nr] = count;
128		pthread_mutex_unlock(area_mutex(gopts->area_dst, page_nr, gopts));
129	}
130
131	return NULL;
132}
133
134static int copy_page_retry(uffd_global_test_opts_t *gopts, unsigned long offset)
135{
136	return __copy_page(gopts, offset, true, gopts->test_uffdio_wp);
137}
138
139pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;
140
141static void *uffd_read_thread(void *arg)
142{
143	struct uffd_args *args = (struct uffd_args *)arg;
144	uffd_global_test_opts_t *gopts = args->gopts;
145	struct uffd_msg msg;
146
147	pthread_mutex_unlock(&uffd_read_mutex);
148	/* from here cancellation is ok */
149
150	for (;;) {
151		if (uffd_read_msg(gopts, &msg))
152			continue;
153		uffd_handle_page_fault(gopts, &msg, args);
154	}
155
156	return NULL;
157}
158
159static void *background_thread(void *arg)
160{
161	struct uffd_args *args = (struct uffd_args *) arg;
162	uffd_global_test_opts_t *gopts = args->gopts;
163	unsigned long cpu = (unsigned long) args->cpu;
164	unsigned long page_nr, start_nr, mid_nr, end_nr;
165
166	start_nr = cpu * gopts->nr_pages_per_cpu;
167	end_nr = (cpu+1) * gopts->nr_pages_per_cpu;
168	mid_nr = (start_nr + end_nr) / 2;
169
170	/* Copy the first half of the pages */
171	for (page_nr = start_nr; page_nr < mid_nr; page_nr++)
172		copy_page_retry(gopts, page_nr * gopts->page_size);
173
174	/*
175	 * If we need to test uffd-wp, set it up now.  Then we'll have
176	 * at least the first half of the pages mapped already which
177	 * can be write-protected for testing
178	 */
179	if (gopts->test_uffdio_wp)
180		wp_range(gopts->uffd, (unsigned long)gopts->area_dst + start_nr * gopts->page_size,
181			gopts->nr_pages_per_cpu * gopts->page_size, true);
182
183	/*
184	 * Continue the 2nd half of the page copying, handling write
185	 * protection faults if any
186	 */
187	for (page_nr = mid_nr; page_nr < end_nr; page_nr++)
188		copy_page_retry(gopts, page_nr * gopts->page_size);
189
190	return NULL;
191}
192
193static int stress(struct uffd_args *args)
194{
195	unsigned long cpu;
196	uffd_global_test_opts_t *gopts = args->gopts;
197	pthread_t locking_threads[gopts->nr_parallel];
198	pthread_t uffd_threads[gopts->nr_parallel];
199	pthread_t background_threads[gopts->nr_parallel];
200
201	gopts->finished = 0;
202	for (cpu = 0; cpu < gopts->nr_parallel; cpu++) {
203		if (pthread_create(&locking_threads[cpu], &attr,
204				   locking_thread, (void *)&args[cpu]))
205			return 1;
206		if (bounces & BOUNCE_POLL) {
207			if (pthread_create(&uffd_threads[cpu],
208					   &attr,
209					   uffd_poll_thread,
210					   (void *) &args[cpu]))
211				err("uffd_poll_thread create");
212		} else {
213			if (pthread_create(&uffd_threads[cpu], &attr,
214					   uffd_read_thread,
215					   (void *)&args[cpu]))
216				return 1;
217			pthread_mutex_lock(&uffd_read_mutex);
218		}
219		if (pthread_create(&background_threads[cpu], &attr,
220				   background_thread, (void *)&args[cpu]))
221			return 1;
222	}
223	for (cpu = 0; cpu < gopts->nr_parallel; cpu++)
224		if (pthread_join(background_threads[cpu], NULL))
225			return 1;
226
227	/*
228	 * Be strict and immediately zap area_src, the whole area has
229	 * been transferred already by the background treads. The
230	 * area_src could then be faulted in a racy way by still
231	 * running uffdio_threads reading zeropages after we zapped
232	 * area_src (but they're guaranteed to get -EEXIST from
233	 * UFFDIO_COPY without writing zero pages into area_dst
234	 * because the background threads already completed).
235	 */
236	uffd_test_ops->release_pages(gopts, gopts->area_src);
237
238	gopts->finished = 1;
239	for (cpu = 0; cpu < gopts->nr_parallel; cpu++)
240		if (pthread_join(locking_threads[cpu], NULL))
241			return 1;
242
243	for (cpu = 0; cpu < gopts->nr_parallel; cpu++) {
244		char c = '\0';
245		if (bounces & BOUNCE_POLL) {
246			if (write(gopts->pipefd[cpu*2+1], &c, 1) != 1)
247				err("pipefd write error");
248			if (pthread_join(uffd_threads[cpu],
249					 (void *)&args[cpu]))
250				return 1;
251		} else {
252			if (pthread_cancel(uffd_threads[cpu]))
253				return 1;
254			if (pthread_join(uffd_threads[cpu], NULL))
255				return 1;
256		}
257	}
258
259	return 0;
260}
261
262static int userfaultfd_stress(uffd_global_test_opts_t *gopts)
263{
264	void *area;
265	unsigned long nr;
266	struct uffd_args args[gopts->nr_parallel];
267	uint64_t mem_size = gopts->nr_pages * gopts->page_size;
268	int flags = 0;
269
270	memset(args, 0, sizeof(struct uffd_args) * gopts->nr_parallel);
271
272	if (features & UFFD_FEATURE_WP_UNPOPULATED && gopts->test_type == TEST_ANON)
273		flags = UFFD_FEATURE_WP_UNPOPULATED;
274
275	if (uffd_test_ctx_init(gopts, flags, NULL))
276		err("context init failed");
277
278	if (posix_memalign(&area, gopts->page_size, gopts->page_size))
279		err("out of memory");
280	zeropage = area;
281	bzero(zeropage, gopts->page_size);
282
283	pthread_mutex_lock(&uffd_read_mutex);
284
285	pthread_attr_init(&attr);
286	pthread_attr_setstacksize(&attr, 16*1024*1024);
287
288	while (bounces--) {
289		printf("bounces: %d, mode:", bounces);
290		if (bounces & BOUNCE_RANDOM)
291			printf(" rnd");
292		if (bounces & BOUNCE_RACINGFAULTS)
293			printf(" racing");
294		if (bounces & BOUNCE_VERIFY)
295			printf(" ver");
296		if (bounces & BOUNCE_POLL)
297			printf(" poll");
298		else
299			printf(" read");
300		printf(", ");
301		fflush(stdout);
302
303		if (bounces & BOUNCE_POLL)
304			fcntl(gopts->uffd, F_SETFL, gopts->uffd_flags | O_NONBLOCK);
305		else
306			fcntl(gopts->uffd, F_SETFL, gopts->uffd_flags & ~O_NONBLOCK);
307
308		/* register */
309		if (uffd_register(gopts->uffd, gopts->area_dst, mem_size,
310				  true, gopts->test_uffdio_wp, false))
311			err("register failure");
312
313		if (gopts->area_dst_alias) {
314			if (uffd_register(gopts->uffd, gopts->area_dst_alias, mem_size,
315					  true, gopts->test_uffdio_wp, false))
316				err("register failure alias");
317		}
318
319		/*
320		 * The madvise done previously isn't enough: some
321		 * uffd_thread could have read userfaults (one of
322		 * those already resolved by the background thread)
323		 * and it may be in the process of calling
324		 * UFFDIO_COPY. UFFDIO_COPY will read the zapped
325		 * area_src and it would map a zero page in it (of
326		 * course such a UFFDIO_COPY is perfectly safe as it'd
327		 * return -EEXIST). The problem comes at the next
328		 * bounce though: that racing UFFDIO_COPY would
329		 * generate zeropages in the area_src, so invalidating
330		 * the previous MADV_DONTNEED. Without this additional
331		 * MADV_DONTNEED those zeropages leftovers in the
332		 * area_src would lead to -EEXIST failure during the
333		 * next bounce, effectively leaving a zeropage in the
334		 * area_dst.
335		 *
336		 * Try to comment this out madvise to see the memory
337		 * corruption being caught pretty quick.
338		 *
339		 * khugepaged is also inhibited to collapse THP after
340		 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
341		 * required to MADV_DONTNEED here.
342		 */
343		uffd_test_ops->release_pages(gopts, gopts->area_dst);
344
345		uffd_stats_reset(gopts, args, gopts->nr_parallel);
346
347		/* bounce pass */
348		if (stress(args)) {
349			uffd_test_ctx_clear(gopts);
350			return 1;
351		}
352
353		/* Clear all the write protections if there is any */
354		if (gopts->test_uffdio_wp)
355			wp_range(gopts->uffd, (unsigned long)gopts->area_dst,
356				 gopts->nr_pages * gopts->page_size, false);
357
358		/* unregister */
359		if (uffd_unregister(gopts->uffd, gopts->area_dst, mem_size))
360			err("unregister failure");
361		if (gopts->area_dst_alias) {
362			if (uffd_unregister(gopts->uffd, gopts->area_dst_alias, mem_size))
363				err("unregister failure alias");
364		}
365
366		/* verification */
367		if (bounces & BOUNCE_VERIFY)
368			for (nr = 0; nr < gopts->nr_pages; nr++)
369				if (*area_count(gopts->area_dst, nr, gopts) !=
370						gopts->count_verify[nr])
371					err("error area_count %llu %llu %lu\n",
372					    *area_count(gopts->area_src, nr, gopts),
373					    gopts->count_verify[nr], nr);
374
375		/* prepare next bounce */
376		swap(gopts->area_src, gopts->area_dst);
377
378		swap(gopts->area_src_alias, gopts->area_dst_alias);
379
380		uffd_stats_report(args, gopts->nr_parallel);
381	}
382	uffd_test_ctx_clear(gopts);
383
384	return 0;
385}
386
387static void set_test_type(uffd_global_test_opts_t *gopts, const char *type)
388{
389	if (!strcmp(type, "anon")) {
390		gopts->test_type = TEST_ANON;
391		uffd_test_ops = &anon_uffd_test_ops;
392	} else if (!strcmp(type, "hugetlb")) {
393		gopts->test_type = TEST_HUGETLB;
394		uffd_test_ops = &hugetlb_uffd_test_ops;
395		gopts->map_shared = true;
396	} else if (!strcmp(type, "hugetlb-private")) {
397		gopts->test_type = TEST_HUGETLB;
398		uffd_test_ops = &hugetlb_uffd_test_ops;
399	} else if (!strcmp(type, "shmem")) {
400		gopts->map_shared = true;
401		gopts->test_type = TEST_SHMEM;
402		uffd_test_ops = &shmem_uffd_test_ops;
403	} else if (!strcmp(type, "shmem-private")) {
404		gopts->test_type = TEST_SHMEM;
405		uffd_test_ops = &shmem_uffd_test_ops;
406	}
407}
408
409static void parse_test_type_arg(uffd_global_test_opts_t *gopts, const char *raw_type)
410{
411	set_test_type(gopts, raw_type);
412
413	if (!gopts->test_type)
414		err("failed to parse test type argument: '%s'", raw_type);
415
416	if (gopts->test_type == TEST_HUGETLB)
417		gopts->page_size = default_huge_page_size();
418	else
419		gopts->page_size = sysconf(_SC_PAGE_SIZE);
420
421	if (!gopts->page_size)
422		err("Unable to determine page size");
423	if ((unsigned long) area_count(NULL, 0, gopts) + sizeof(unsigned long long) * 2
424	    > gopts->page_size)
425		err("Impossible to run this test");
426
427	/*
428	 * Whether we can test certain features depends not just on test type,
429	 * but also on whether or not this particular kernel supports the
430	 * feature.
431	 */
432
433	if (uffd_get_features(&features) && errno == ENOENT)
434		ksft_exit_skip("failed to get available features (%d)\n", errno);
435
436	gopts->test_uffdio_wp = gopts->test_uffdio_wp &&
437		(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
438
439	if (gopts->test_type != TEST_ANON && !(features & UFFD_FEATURE_WP_HUGETLBFS_SHMEM))
440		gopts->test_uffdio_wp = false;
441
442	close(gopts->uffd);
443	gopts->uffd = -1;
444}
445
446static void sigalrm(int sig)
447{
448	if (sig != SIGALRM)
449		abort();
450	gopts->test_uffdio_copy_eexist = true;
451	alarm(ALARM_INTERVAL_SECS);
452}
453
454int main(int argc, char **argv)
455{
456	unsigned long nr_cpus;
457	size_t bytes;
458
459	gopts = (uffd_global_test_opts_t *) malloc(sizeof(uffd_global_test_opts_t));
460
461	if (argc < 4)
462		usage();
463
464	if (signal(SIGALRM, sigalrm) == SIG_ERR)
465		err("failed to arm SIGALRM");
466	alarm(ALARM_INTERVAL_SECS);
467
468	parse_test_type_arg(gopts, argv[1]);
469	bytes = atol(argv[2]) * 1024 * 1024;
470
471	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
472	if (nr_cpus > 32) {
473		/* Don't let calculation below go to zero. */
474		ksft_print_msg("_SC_NPROCESSORS_ONLN (%lu) too large, capping nr_threads to 32\n",
475			       nr_cpus);
476		gopts->nr_parallel = 32;
477	} else {
478		gopts->nr_parallel = nr_cpus;
479	}
480
481	/*
482	 * src and dst each require bytes / page_size number of hugepages.
483	 * Ensure nr_parallel - 1 hugepages on top of that to account
484	 * for racy extra reservation of hugepages.
485	 */
486	if (gopts->test_type == TEST_HUGETLB &&
487	   get_free_hugepages() < 2 * (bytes / gopts->page_size) + gopts->nr_parallel - 1) {
488		printf("skip: Skipping userfaultfd... not enough hugepages\n");
489		return KSFT_SKIP;
490	}
491
492	gopts->nr_pages_per_cpu = bytes / gopts->page_size / gopts->nr_parallel;
493	if (!gopts->nr_pages_per_cpu) {
494		_err("pages_per_cpu = 0, cannot test (%lu / %lu / %lu)",
495			bytes, gopts->page_size, gopts->nr_parallel);
496		usage();
497	}
498
499	bounces = atoi(argv[3]);
500	if (bounces <= 0) {
501		_err("invalid bounces");
502		usage();
503	}
504	gopts->nr_pages = gopts->nr_pages_per_cpu * gopts->nr_parallel;
505
506	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
507	       gopts->nr_pages, gopts->nr_pages_per_cpu);
508	return userfaultfd_stress(gopts);
509}
510
511#else /* __NR_userfaultfd */
512
513#warning "missing __NR_userfaultfd definition"
514
515int main(void)
516{
517	printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n");
518	return KSFT_SKIP;
519}
520
521#endif /* __NR_userfaultfd */