1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * KVM demand paging test
4 * Adapted from dirty_log_test.c
5 *
6 * Copyright (C) 2018, Red Hat, Inc.
7 * Copyright (C) 2019, Google, Inc.
8 */
9 #include <inttypes.h>
10 #include <stdio.h>
11 #include <stdlib.h>
12 #include <time.h>
13 #include <pthread.h>
14 #include <linux/userfaultfd.h>
15 #include <sys/syscall.h>
16
17 #include "kvm_util.h"
18 #include "test_util.h"
19 #include "memstress.h"
20 #include "guest_modes.h"
21 #include "ucall_common.h"
22 #include "userfaultfd_util.h"
23
24 #ifdef __NR_userfaultfd
25
26 static int nr_vcpus = 1;
27 static uint64_t guest_percpu_mem_size = DEFAULT_PER_VCPU_MEM_SIZE;
28
29 static size_t demand_paging_size;
30 static char *guest_data_prototype;
31
vcpu_worker(struct memstress_vcpu_args * vcpu_args)32 static void vcpu_worker(struct memstress_vcpu_args *vcpu_args)
33 {
34 struct kvm_vcpu *vcpu = vcpu_args->vcpu;
35 int vcpu_idx = vcpu_args->vcpu_idx;
36 struct kvm_run *run = vcpu->run;
37 struct timespec start;
38 struct timespec ts_diff;
39 int ret;
40
41 clock_gettime(CLOCK_MONOTONIC, &start);
42
43 /* Let the guest access its memory */
44 ret = _vcpu_run(vcpu);
45 TEST_ASSERT(ret == 0, "vcpu_run failed: %d", ret);
46 if (get_ucall(vcpu, NULL) != UCALL_SYNC) {
47 TEST_ASSERT(false,
48 "Invalid guest sync status: exit_reason=%s",
49 exit_reason_str(run->exit_reason));
50 }
51
52 ts_diff = timespec_elapsed(start);
53 PER_VCPU_DEBUG("vCPU %d execution time: %ld.%.9lds\n", vcpu_idx,
54 ts_diff.tv_sec, ts_diff.tv_nsec);
55 }
56
handle_uffd_page_request(int uffd_mode,int uffd,struct uffd_msg * msg)57 static int handle_uffd_page_request(int uffd_mode, int uffd,
58 struct uffd_msg *msg)
59 {
60 pid_t tid = syscall(__NR_gettid);
61 uint64_t addr = msg->arg.pagefault.address;
62 struct timespec start;
63 struct timespec ts_diff;
64 int r;
65
66 clock_gettime(CLOCK_MONOTONIC, &start);
67
68 if (uffd_mode == UFFDIO_REGISTER_MODE_MISSING) {
69 struct uffdio_copy copy;
70
71 copy.src = (uint64_t)guest_data_prototype;
72 copy.dst = addr;
73 copy.len = demand_paging_size;
74 copy.mode = 0;
75
76 r = ioctl(uffd, UFFDIO_COPY, ©);
77 /*
78 * With multiple vCPU threads fault on a single page and there are
79 * multiple readers for the UFFD, at least one of the UFFDIO_COPYs
80 * will fail with EEXIST: handle that case without signaling an
81 * error.
82 *
83 * Note that this also suppress any EEXISTs occurring from,
84 * e.g., the first UFFDIO_COPY/CONTINUEs on a page. That never
85 * happens here, but a realistic VMM might potentially maintain
86 * some external state to correctly surface EEXISTs to userspace
87 * (or prevent duplicate COPY/CONTINUEs in the first place).
88 */
89 if (r == -1 && errno != EEXIST) {
90 pr_info("Failed UFFDIO_COPY in 0x%lx from thread %d, errno = %d\n",
91 addr, tid, errno);
92 return r;
93 }
94 } else if (uffd_mode == UFFDIO_REGISTER_MODE_MINOR) {
95 struct uffdio_continue cont = {0};
96
97 cont.range.start = addr;
98 cont.range.len = demand_paging_size;
99
100 r = ioctl(uffd, UFFDIO_CONTINUE, &cont);
101 /*
102 * With multiple vCPU threads fault on a single page and there are
103 * multiple readers for the UFFD, at least one of the UFFDIO_COPYs
104 * will fail with EEXIST: handle that case without signaling an
105 * error.
106 *
107 * Note that this also suppress any EEXISTs occurring from,
108 * e.g., the first UFFDIO_COPY/CONTINUEs on a page. That never
109 * happens here, but a realistic VMM might potentially maintain
110 * some external state to correctly surface EEXISTs to userspace
111 * (or prevent duplicate COPY/CONTINUEs in the first place).
112 */
113 if (r == -1 && errno != EEXIST) {
114 pr_info("Failed UFFDIO_CONTINUE in 0x%lx, thread %d, errno = %d\n",
115 addr, tid, errno);
116 return r;
117 }
118 } else {
119 TEST_FAIL("Invalid uffd mode %d", uffd_mode);
120 }
121
122 ts_diff = timespec_elapsed(start);
123
124 PER_PAGE_DEBUG("UFFD page-in %d \t%ld ns\n", tid,
125 timespec_to_ns(ts_diff));
126 PER_PAGE_DEBUG("Paged in %ld bytes at 0x%lx from thread %d\n",
127 demand_paging_size, addr, tid);
128
129 return 0;
130 }
131
132 struct test_params {
133 int uffd_mode;
134 bool single_uffd;
135 useconds_t uffd_delay;
136 int readers_per_uffd;
137 enum vm_mem_backing_src_type src_type;
138 bool partition_vcpu_memory_access;
139 };
140
prefault_mem(void * alias,uint64_t len)141 static void prefault_mem(void *alias, uint64_t len)
142 {
143 size_t p;
144
145 TEST_ASSERT(alias != NULL, "Alias required for minor faults");
146 for (p = 0; p < (len / demand_paging_size); ++p) {
147 memcpy(alias + (p * demand_paging_size),
148 guest_data_prototype, demand_paging_size);
149 }
150 }
151
run_test(enum vm_guest_mode mode,void * arg)152 static void run_test(enum vm_guest_mode mode, void *arg)
153 {
154 struct memstress_vcpu_args *vcpu_args;
155 struct test_params *p = arg;
156 struct uffd_desc **uffd_descs = NULL;
157 uint64_t uffd_region_size;
158 struct timespec start;
159 struct timespec ts_diff;
160 double vcpu_paging_rate;
161 struct kvm_vm *vm;
162 int i, num_uffds = 0;
163
164 vm = memstress_create_vm(mode, nr_vcpus, guest_percpu_mem_size, 1,
165 p->src_type, p->partition_vcpu_memory_access);
166
167 demand_paging_size = get_backing_src_pagesz(p->src_type);
168
169 guest_data_prototype = malloc(demand_paging_size);
170 TEST_ASSERT(guest_data_prototype,
171 "Failed to allocate buffer for guest data pattern");
172 memset(guest_data_prototype, 0xAB, demand_paging_size);
173
174 if (p->uffd_mode == UFFDIO_REGISTER_MODE_MINOR) {
175 num_uffds = p->single_uffd ? 1 : nr_vcpus;
176 for (i = 0; i < num_uffds; i++) {
177 vcpu_args = &memstress_args.vcpu_args[i];
178 prefault_mem(addr_gpa2alias(vm, vcpu_args->gpa),
179 vcpu_args->pages * memstress_args.guest_page_size);
180 }
181 }
182
183 if (p->uffd_mode) {
184 num_uffds = p->single_uffd ? 1 : nr_vcpus;
185 uffd_region_size = nr_vcpus * guest_percpu_mem_size / num_uffds;
186
187 uffd_descs = malloc(num_uffds * sizeof(struct uffd_desc *));
188 TEST_ASSERT(uffd_descs, "Memory allocation failed");
189 for (i = 0; i < num_uffds; i++) {
190 struct memstress_vcpu_args *vcpu_args;
191 void *vcpu_hva;
192
193 vcpu_args = &memstress_args.vcpu_args[i];
194
195 /* Cache the host addresses of the region */
196 vcpu_hva = addr_gpa2hva(vm, vcpu_args->gpa);
197 /*
198 * Set up user fault fd to handle demand paging
199 * requests.
200 */
201 uffd_descs[i] = uffd_setup_demand_paging(
202 p->uffd_mode, p->uffd_delay, vcpu_hva,
203 uffd_region_size,
204 p->readers_per_uffd,
205 &handle_uffd_page_request);
206 }
207 }
208
209 pr_info("Finished creating vCPUs and starting uffd threads\n");
210
211 clock_gettime(CLOCK_MONOTONIC, &start);
212 memstress_start_vcpu_threads(nr_vcpus, vcpu_worker);
213 pr_info("Started all vCPUs\n");
214
215 memstress_join_vcpu_threads(nr_vcpus);
216 ts_diff = timespec_elapsed(start);
217 pr_info("All vCPU threads joined\n");
218
219 if (p->uffd_mode) {
220 /* Tell the user fault fd handler threads to quit */
221 for (i = 0; i < num_uffds; i++)
222 uffd_stop_demand_paging(uffd_descs[i]);
223 }
224
225 pr_info("Total guest execution time:\t%ld.%.9lds\n",
226 ts_diff.tv_sec, ts_diff.tv_nsec);
227
228 vcpu_paging_rate = memstress_args.vcpu_args[0].pages /
229 ((double)ts_diff.tv_sec + (double)ts_diff.tv_nsec / NSEC_PER_SEC);
230 pr_info("Per-vcpu demand paging rate:\t%f pgs/sec/vcpu\n",
231 vcpu_paging_rate);
232 pr_info("Overall demand paging rate:\t%f pgs/sec\n",
233 vcpu_paging_rate * nr_vcpus);
234
235 memstress_destroy_vm(vm);
236
237 free(guest_data_prototype);
238 if (p->uffd_mode)
239 free(uffd_descs);
240 }
241
help(char * name)242 static void help(char *name)
243 {
244 puts("");
245 printf("usage: %s [-h] [-m vm_mode] [-u uffd_mode] [-a]\n"
246 " [-d uffd_delay_usec] [-r readers_per_uffd] [-b memory]\n"
247 " [-s type] [-v vcpus] [-c cpu_list] [-o]\n", name);
248 guest_modes_help();
249 printf(" -u: use userfaultfd to handle vCPU page faults. Mode is a\n"
250 " UFFD registration mode: 'MISSING' or 'MINOR'.\n");
251 kvm_print_vcpu_pinning_help();
252 printf(" -a: Use a single userfaultfd for all of guest memory, instead of\n"
253 " creating one for each region paged by a unique vCPU\n"
254 " Set implicitly with -o, and no effect without -u.\n");
255 printf(" -d: add a delay in usec to the User Fault\n"
256 " FD handler to simulate demand paging\n"
257 " overheads. Ignored without -u.\n");
258 printf(" -r: Set the number of reader threads per uffd.\n");
259 printf(" -b: specify the size of the memory region which should be\n"
260 " demand paged by each vCPU. e.g. 10M or 3G.\n"
261 " Default: 1G\n");
262 backing_src_help("-s");
263 printf(" -v: specify the number of vCPUs to run.\n");
264 printf(" -o: Overlap guest memory accesses instead of partitioning\n"
265 " them into a separate region of memory for each vCPU.\n");
266 puts("");
267 exit(0);
268 }
269
main(int argc,char * argv[])270 int main(int argc, char *argv[])
271 {
272 int max_vcpus = kvm_check_cap(KVM_CAP_MAX_VCPUS);
273 const char *cpulist = NULL;
274 struct test_params p = {
275 .src_type = DEFAULT_VM_MEM_SRC,
276 .partition_vcpu_memory_access = true,
277 .readers_per_uffd = 1,
278 .single_uffd = false,
279 };
280 int opt;
281
282 guest_modes_append_default();
283
284 while ((opt = getopt(argc, argv, "ahom:u:d:b:s:v:c:r:")) != -1) {
285 switch (opt) {
286 case 'm':
287 guest_modes_cmdline(optarg);
288 break;
289 case 'u':
290 if (!strcmp("MISSING", optarg))
291 p.uffd_mode = UFFDIO_REGISTER_MODE_MISSING;
292 else if (!strcmp("MINOR", optarg))
293 p.uffd_mode = UFFDIO_REGISTER_MODE_MINOR;
294 TEST_ASSERT(p.uffd_mode, "UFFD mode must be 'MISSING' or 'MINOR'.");
295 break;
296 case 'a':
297 p.single_uffd = true;
298 break;
299 case 'd':
300 p.uffd_delay = strtoul(optarg, NULL, 0);
301 TEST_ASSERT(p.uffd_delay >= 0, "A negative UFFD delay is not supported.");
302 break;
303 case 'b':
304 guest_percpu_mem_size = parse_size(optarg);
305 break;
306 case 's':
307 p.src_type = parse_backing_src_type(optarg);
308 break;
309 case 'v':
310 nr_vcpus = atoi_positive("Number of vCPUs", optarg);
311 TEST_ASSERT(nr_vcpus <= max_vcpus,
312 "Invalid number of vcpus, must be between 1 and %d", max_vcpus);
313 break;
314 case 'c':
315 cpulist = optarg;
316 break;
317 case 'o':
318 p.partition_vcpu_memory_access = false;
319 p.single_uffd = true;
320 break;
321 case 'r':
322 p.readers_per_uffd = atoi(optarg);
323 TEST_ASSERT(p.readers_per_uffd >= 1,
324 "Invalid number of readers per uffd %d: must be >=1",
325 p.readers_per_uffd);
326 break;
327 case 'h':
328 default:
329 help(argv[0]);
330 break;
331 }
332 }
333
334 if (p.uffd_mode == UFFDIO_REGISTER_MODE_MINOR &&
335 !backing_src_is_shared(p.src_type)) {
336 TEST_FAIL("userfaultfd MINOR mode requires shared memory; pick a different -s");
337 }
338
339 if (cpulist) {
340 kvm_parse_vcpu_pinning(cpulist, memstress_args.vcpu_to_pcpu,
341 nr_vcpus);
342 memstress_args.pin_vcpus = true;
343 }
344
345 for_each_guest_mode(run_test, &p);
346
347 return 0;
348 }
349
350 #else /* __NR_userfaultfd */
351
352 #warning "missing __NR_userfaultfd definition"
353
main(void)354 int main(void)
355 {
356 print_skip("__NR_userfaultfd must be present for userfaultfd test");
357 return KSFT_SKIP;
358 }
359
360 #endif /* __NR_userfaultfd */
361