xref: /linux/arch/riscv/kernel/sys_hwprobe.c (revision ba23adb6533149df33b9a247f31a87227b3c86d5)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * The hwprobe interface, for allowing userspace to probe to see which features
4  * are supported by the hardware.  See Documentation/arch/riscv/hwprobe.rst for
5  * more details.
6  */
7 #include <linux/syscalls.h>
8 #include <linux/completion.h>
9 #include <linux/atomic.h>
10 #include <linux/once.h>
11 #include <asm/cacheflush.h>
12 #include <asm/cpufeature.h>
13 #include <asm/hwprobe.h>
14 #include <asm/processor.h>
15 #include <asm/delay.h>
16 #include <asm/sbi.h>
17 #include <asm/switch_to.h>
18 #include <asm/uaccess.h>
19 #include <asm/unistd.h>
20 #include <asm/vector.h>
21 #include <asm/vendor_extensions/mips_hwprobe.h>
22 #include <asm/vendor_extensions/sifive_hwprobe.h>
23 #include <asm/vendor_extensions/thead_hwprobe.h>
24 #include <vdso/vsyscall.h>
25 
26 
27 #define EXT_KEY(isa_arg, ext, pv, missing)					\
28 	do {										\
29 		if (__riscv_isa_extension_available(isa_arg, RISCV_ISA_EXT_##ext))	\
30 			pv |= RISCV_HWPROBE_EXT_##ext;				\
31 		else									\
32 			missing |= RISCV_HWPROBE_EXT_##ext;				\
33 	} while (false)
34 
hwprobe_arch_id(struct riscv_hwprobe * pair,const struct cpumask * cpus)35 static void hwprobe_arch_id(struct riscv_hwprobe *pair,
36 			    const struct cpumask *cpus)
37 {
38 	u64 id = -1ULL;
39 	bool first = true;
40 	int cpu;
41 
42 	if (pair->key != RISCV_HWPROBE_KEY_MVENDORID &&
43 	    pair->key != RISCV_HWPROBE_KEY_MIMPID &&
44 	    pair->key != RISCV_HWPROBE_KEY_MARCHID)
45 		goto out;
46 
47 	for_each_cpu(cpu, cpus) {
48 		u64 cpu_id;
49 
50 		switch (pair->key) {
51 		case RISCV_HWPROBE_KEY_MVENDORID:
52 			cpu_id = riscv_cached_mvendorid(cpu);
53 			break;
54 		case RISCV_HWPROBE_KEY_MIMPID:
55 			cpu_id = riscv_cached_mimpid(cpu);
56 			break;
57 		case RISCV_HWPROBE_KEY_MARCHID:
58 			cpu_id = riscv_cached_marchid(cpu);
59 			break;
60 		}
61 
62 		if (first) {
63 			id = cpu_id;
64 			first = false;
65 		}
66 
67 		/*
68 		 * If there's a mismatch for the given set, return -1 in the
69 		 * value.
70 		 */
71 		if (id != cpu_id) {
72 			id = -1ULL;
73 			break;
74 		}
75 	}
76 
77 out:
78 	pair->value = id;
79 }
80 
hwprobe_isa_ext0(struct riscv_hwprobe * pair,const struct cpumask * cpus)81 static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
82 			     const struct cpumask *cpus)
83 {
84 	int cpu;
85 	u64 missing = 0;
86 
87 	pair->value = 0;
88 	if (has_fpu())
89 		pair->value |= RISCV_HWPROBE_IMA_FD;
90 
91 	if (riscv_isa_extension_available(NULL, c))
92 		pair->value |= RISCV_HWPROBE_IMA_C;
93 
94 	if (has_vector() && riscv_isa_extension_available(NULL, v))
95 		pair->value |= RISCV_HWPROBE_IMA_V;
96 
97 	/*
98 	 * Loop through and record extensions that 1) anyone has, and 2) anyone
99 	 * doesn't have.
100 	 */
101 	for_each_cpu(cpu, cpus) {
102 		struct riscv_isainfo *isainfo = &hart_isa[cpu];
103 
104 		/*
105 		 * Only use EXT_KEY() for extensions which can be exposed to userspace,
106 		 * regardless of the kernel's configuration, as no other checks, besides
107 		 * presence in the hart_isa bitmap, are made.
108 		 */
109 		EXT_KEY(isainfo->isa, ZAAMO, pair->value, missing);
110 		EXT_KEY(isainfo->isa, ZABHA, pair->value, missing);
111 		EXT_KEY(isainfo->isa, ZACAS, pair->value, missing);
112 		EXT_KEY(isainfo->isa, ZALASR, pair->value, missing);
113 		EXT_KEY(isainfo->isa, ZALRSC, pair->value, missing);
114 		EXT_KEY(isainfo->isa, ZAWRS, pair->value, missing);
115 		EXT_KEY(isainfo->isa, ZBA, pair->value, missing);
116 		EXT_KEY(isainfo->isa, ZBB, pair->value, missing);
117 		EXT_KEY(isainfo->isa, ZBC, pair->value, missing);
118 		EXT_KEY(isainfo->isa, ZBKB, pair->value, missing);
119 		EXT_KEY(isainfo->isa, ZBKC, pair->value, missing);
120 		EXT_KEY(isainfo->isa, ZBKX, pair->value, missing);
121 		EXT_KEY(isainfo->isa, ZBS, pair->value, missing);
122 		EXT_KEY(isainfo->isa, ZCA, pair->value, missing);
123 		EXT_KEY(isainfo->isa, ZCB, pair->value, missing);
124 		EXT_KEY(isainfo->isa, ZCLSD, pair->value, missing);
125 		EXT_KEY(isainfo->isa, ZCMOP, pair->value, missing);
126 		EXT_KEY(isainfo->isa, ZICBOM, pair->value, missing);
127 		EXT_KEY(isainfo->isa, ZICBOP, pair->value, missing);
128 		EXT_KEY(isainfo->isa, ZICBOZ, pair->value, missing);
129 		EXT_KEY(isainfo->isa, ZICFILP, pair->value, missing);
130 		EXT_KEY(isainfo->isa, ZICNTR, pair->value, missing);
131 		EXT_KEY(isainfo->isa, ZICOND, pair->value, missing);
132 		EXT_KEY(isainfo->isa, ZIHINTNTL, pair->value, missing);
133 		EXT_KEY(isainfo->isa, ZIHINTPAUSE, pair->value, missing);
134 		EXT_KEY(isainfo->isa, ZIHPM, pair->value, missing);
135 		EXT_KEY(isainfo->isa, ZILSD, pair->value, missing);
136 		EXT_KEY(isainfo->isa, ZIMOP, pair->value, missing);
137 		EXT_KEY(isainfo->isa, ZKND, pair->value, missing);
138 		EXT_KEY(isainfo->isa, ZKNE, pair->value, missing);
139 		EXT_KEY(isainfo->isa, ZKNH, pair->value, missing);
140 		EXT_KEY(isainfo->isa, ZKSED, pair->value, missing);
141 		EXT_KEY(isainfo->isa, ZKSH, pair->value, missing);
142 		EXT_KEY(isainfo->isa, ZKT, pair->value, missing);
143 		EXT_KEY(isainfo->isa, ZTSO, pair->value, missing);
144 
145 		/*
146 		 * All the following extensions must depend on the kernel
147 		 * support of V.
148 		 */
149 		if (has_vector()) {
150 			EXT_KEY(isainfo->isa, ZVBB, pair->value, missing);
151 			EXT_KEY(isainfo->isa, ZVBC, pair->value, missing);
152 			EXT_KEY(isainfo->isa, ZVE32F, pair->value, missing);
153 			EXT_KEY(isainfo->isa, ZVE32X, pair->value, missing);
154 			EXT_KEY(isainfo->isa, ZVE64D, pair->value, missing);
155 			EXT_KEY(isainfo->isa, ZVE64F, pair->value, missing);
156 			EXT_KEY(isainfo->isa, ZVE64X, pair->value, missing);
157 			EXT_KEY(isainfo->isa, ZVFBFMIN, pair->value, missing);
158 			EXT_KEY(isainfo->isa, ZVFBFWMA, pair->value, missing);
159 			EXT_KEY(isainfo->isa, ZVFH, pair->value, missing);
160 			EXT_KEY(isainfo->isa, ZVFHMIN, pair->value, missing);
161 			EXT_KEY(isainfo->isa, ZVKB, pair->value, missing);
162 			EXT_KEY(isainfo->isa, ZVKG, pair->value, missing);
163 			EXT_KEY(isainfo->isa, ZVKNED, pair->value, missing);
164 			EXT_KEY(isainfo->isa, ZVKNHA, pair->value, missing);
165 			EXT_KEY(isainfo->isa, ZVKNHB, pair->value, missing);
166 			EXT_KEY(isainfo->isa, ZVKSED, pair->value, missing);
167 			EXT_KEY(isainfo->isa, ZVKSH, pair->value, missing);
168 			EXT_KEY(isainfo->isa, ZVKT, pair->value, missing);
169 		}
170 
171 		EXT_KEY(isainfo->isa, ZCD, pair->value, missing);
172 		EXT_KEY(isainfo->isa, ZCF, pair->value, missing);
173 		EXT_KEY(isainfo->isa, ZFA, pair->value, missing);
174 		EXT_KEY(isainfo->isa, ZFBFMIN, pair->value, missing);
175 		EXT_KEY(isainfo->isa, ZFH, pair->value, missing);
176 		EXT_KEY(isainfo->isa, ZFHMIN, pair->value, missing);
177 
178 		if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM))
179 			EXT_KEY(isainfo->isa, SUPM, pair->value, missing);
180 	}
181 
182 	/* Now turn off reporting features if any CPU is missing it. */
183 	pair->value &= ~missing;
184 }
185 
hwprobe_isa_ext1(struct riscv_hwprobe * pair,const struct cpumask * cpus)186 static void hwprobe_isa_ext1(struct riscv_hwprobe *pair,
187 			     const struct cpumask *cpus)
188 {
189 	int cpu;
190 	u64 missing = 0;
191 
192 	pair->value = 0;
193 
194 	/*
195 	 * Loop through and record extensions that 1) anyone has, and 2) anyone
196 	 * doesn't have.
197 	 */
198 	for_each_cpu(cpu, cpus) {
199 		struct riscv_isainfo *isainfo = &hart_isa[cpu];
200 
201 		/*
202 		 * Only use EXT_KEY() for extensions which can be
203 		 * exposed to userspace, regardless of the kernel's
204 		 * configuration, as no other checks, besides presence
205 		 * in the hart_isa bitmap, are made.
206 		 */
207 		EXT_KEY(isainfo->isa, ZICFISS, pair->value, missing);
208 	}
209 
210 	/* Now turn off reporting features if any CPU is missing it. */
211 	pair->value &= ~missing;
212 }
213 
hwprobe_ext0_has(const struct cpumask * cpus,u64 ext)214 static bool hwprobe_ext0_has(const struct cpumask *cpus, u64 ext)
215 {
216 	struct riscv_hwprobe pair;
217 
218 	hwprobe_isa_ext0(&pair, cpus);
219 	return (pair.value & ext);
220 }
221 
222 #if defined(CONFIG_RISCV_PROBE_UNALIGNED_ACCESS)
hwprobe_misaligned(const struct cpumask * cpus)223 static u64 hwprobe_misaligned(const struct cpumask *cpus)
224 {
225 	int cpu;
226 	u64 perf = -1ULL;
227 
228 	for_each_cpu(cpu, cpus) {
229 		int this_perf = per_cpu(misaligned_access_speed, cpu);
230 
231 		if (perf == -1ULL)
232 			perf = this_perf;
233 
234 		if (perf != this_perf) {
235 			perf = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
236 			break;
237 		}
238 	}
239 
240 	if (perf == -1ULL)
241 		return RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
242 
243 	return perf;
244 }
245 #else
hwprobe_misaligned(const struct cpumask * cpus)246 static u64 hwprobe_misaligned(const struct cpumask *cpus)
247 {
248 	if (IS_ENABLED(CONFIG_RISCV_EFFICIENT_UNALIGNED_ACCESS))
249 		return RISCV_HWPROBE_MISALIGNED_SCALAR_FAST;
250 
251 	if (IS_ENABLED(CONFIG_RISCV_EMULATED_UNALIGNED_ACCESS) && unaligned_ctl_available())
252 		return RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED;
253 
254 	return RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW;
255 }
256 #endif
257 
258 #ifdef CONFIG_RISCV_VECTOR_MISALIGNED
hwprobe_vec_misaligned(const struct cpumask * cpus)259 static u64 hwprobe_vec_misaligned(const struct cpumask *cpus)
260 {
261 	int cpu;
262 	u64 perf = -1ULL;
263 
264 	/* Return if supported or not even if speed wasn't probed */
265 	for_each_cpu(cpu, cpus) {
266 		int this_perf = per_cpu(vector_misaligned_access, cpu);
267 
268 		if (perf == -1ULL)
269 			perf = this_perf;
270 
271 		if (perf != this_perf) {
272 			perf = RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN;
273 			break;
274 		}
275 	}
276 
277 	if (perf == -1ULL)
278 		return RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN;
279 
280 	return perf;
281 }
282 #else
hwprobe_vec_misaligned(const struct cpumask * cpus)283 static u64 hwprobe_vec_misaligned(const struct cpumask *cpus)
284 {
285 	if (IS_ENABLED(CONFIG_RISCV_EFFICIENT_VECTOR_UNALIGNED_ACCESS))
286 		return RISCV_HWPROBE_MISALIGNED_VECTOR_FAST;
287 
288 	if (IS_ENABLED(CONFIG_RISCV_SLOW_VECTOR_UNALIGNED_ACCESS))
289 		return RISCV_HWPROBE_MISALIGNED_VECTOR_SLOW;
290 
291 	return RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN;
292 }
293 #endif
294 
hwprobe_one_pair(struct riscv_hwprobe * pair,const struct cpumask * cpus)295 static void hwprobe_one_pair(struct riscv_hwprobe *pair,
296 			     const struct cpumask *cpus)
297 {
298 	switch (pair->key) {
299 	case RISCV_HWPROBE_KEY_MVENDORID:
300 	case RISCV_HWPROBE_KEY_MARCHID:
301 	case RISCV_HWPROBE_KEY_MIMPID:
302 		hwprobe_arch_id(pair, cpus);
303 		break;
304 	/*
305 	 * The kernel already assumes that the base single-letter ISA
306 	 * extensions are supported on all harts, and only supports the
307 	 * IMA base, so just cheat a bit here and tell that to
308 	 * userspace.
309 	 */
310 	case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
311 		pair->value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA;
312 		break;
313 
314 	case RISCV_HWPROBE_KEY_IMA_EXT_0:
315 		hwprobe_isa_ext0(pair, cpus);
316 		break;
317 
318 	case RISCV_HWPROBE_KEY_IMA_EXT_1:
319 		hwprobe_isa_ext1(pair, cpus);
320 		break;
321 
322 	case RISCV_HWPROBE_KEY_CPUPERF_0:
323 	case RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF:
324 		pair->value = hwprobe_misaligned(cpus);
325 		break;
326 
327 	case RISCV_HWPROBE_KEY_MISALIGNED_VECTOR_PERF:
328 		pair->value = hwprobe_vec_misaligned(cpus);
329 		break;
330 
331 	case RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE:
332 		pair->value = 0;
333 		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOZ))
334 			pair->value = riscv_cboz_block_size;
335 		break;
336 	case RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE:
337 		pair->value = 0;
338 		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOM))
339 			pair->value = riscv_cbom_block_size;
340 		break;
341 	case RISCV_HWPROBE_KEY_ZICBOP_BLOCK_SIZE:
342 		pair->value = 0;
343 		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOP))
344 			pair->value = riscv_cbop_block_size;
345 		break;
346 	case RISCV_HWPROBE_KEY_HIGHEST_VIRT_ADDRESS:
347 		pair->value = user_max_virt_addr();
348 		break;
349 
350 	case RISCV_HWPROBE_KEY_TIME_CSR_FREQ:
351 		pair->value = riscv_timebase;
352 		break;
353 
354 	case RISCV_HWPROBE_KEY_VENDOR_EXT_SIFIVE_0:
355 		hwprobe_isa_vendor_ext_sifive_0(pair, cpus);
356 		break;
357 
358 	case RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0:
359 		hwprobe_isa_vendor_ext_thead_0(pair, cpus);
360 		break;
361 	case RISCV_HWPROBE_KEY_VENDOR_EXT_MIPS_0:
362 		hwprobe_isa_vendor_ext_mips_0(pair, cpus);
363 		break;
364 
365 	/*
366 	 * For forward compatibility, unknown keys don't fail the whole
367 	 * call, but get their element key set to -1 and value set to 0
368 	 * indicating they're unrecognized.
369 	 */
370 	default:
371 		pair->key = -1;
372 		pair->value = 0;
373 		break;
374 	}
375 }
376 
hwprobe_get_values(struct riscv_hwprobe __user * pairs,size_t pair_count,size_t cpusetsize,unsigned long __user * cpus_user,unsigned int flags)377 static int hwprobe_get_values(struct riscv_hwprobe __user *pairs,
378 			      size_t pair_count, size_t cpusetsize,
379 			      unsigned long __user *cpus_user,
380 			      unsigned int flags)
381 {
382 	size_t out;
383 	int ret;
384 	cpumask_t cpus;
385 
386 	/* Check the reserved flags. */
387 	if (flags != 0)
388 		return -EINVAL;
389 
390 	/*
391 	 * The interface supports taking in a CPU mask, and returns values that
392 	 * are consistent across that mask. Allow userspace to specify NULL and
393 	 * 0 as a shortcut to all online CPUs.
394 	 */
395 	cpumask_clear(&cpus);
396 	if (!cpusetsize && !cpus_user) {
397 		cpumask_copy(&cpus, cpu_online_mask);
398 	} else {
399 		if (cpusetsize > cpumask_size())
400 			cpusetsize = cpumask_size();
401 
402 		ret = copy_from_user(&cpus, cpus_user, cpusetsize);
403 		if (ret)
404 			return -EFAULT;
405 
406 		/*
407 		 * Userspace must provide at least one online CPU, without that
408 		 * there's no way to define what is supported.
409 		 */
410 		cpumask_and(&cpus, &cpus, cpu_online_mask);
411 		if (cpumask_empty(&cpus))
412 			return -EINVAL;
413 	}
414 
415 	for (out = 0; out < pair_count; out++, pairs++) {
416 		struct riscv_hwprobe pair;
417 
418 		if (get_user(pair.key, &pairs->key))
419 			return -EFAULT;
420 
421 		pair.value = 0;
422 		hwprobe_one_pair(&pair, &cpus);
423 		ret = put_user(pair.key, &pairs->key);
424 		if (ret == 0)
425 			ret = put_user(pair.value, &pairs->value);
426 
427 		if (ret)
428 			return -EFAULT;
429 	}
430 
431 	return 0;
432 }
433 
hwprobe_get_cpus(struct riscv_hwprobe __user * pairs,size_t pair_count,size_t cpusetsize,unsigned long __user * cpus_user,unsigned int flags)434 static int hwprobe_get_cpus(struct riscv_hwprobe __user *pairs,
435 			    size_t pair_count, size_t cpusetsize,
436 			    unsigned long __user *cpus_user,
437 			    unsigned int flags)
438 {
439 	cpumask_t cpus, one_cpu;
440 	bool clear_all = false;
441 	size_t i;
442 	int ret;
443 
444 	if (flags != RISCV_HWPROBE_WHICH_CPUS)
445 		return -EINVAL;
446 
447 	if (!cpusetsize || !cpus_user)
448 		return -EINVAL;
449 
450 	if (cpusetsize > cpumask_size())
451 		cpusetsize = cpumask_size();
452 
453 	ret = copy_from_user(&cpus, cpus_user, cpusetsize);
454 	if (ret)
455 		return -EFAULT;
456 
457 	if (cpumask_empty(&cpus))
458 		cpumask_copy(&cpus, cpu_online_mask);
459 
460 	cpumask_and(&cpus, &cpus, cpu_online_mask);
461 
462 	cpumask_clear(&one_cpu);
463 
464 	for (i = 0; i < pair_count; i++) {
465 		struct riscv_hwprobe pair, tmp;
466 		int cpu;
467 
468 		ret = copy_from_user(&pair, &pairs[i], sizeof(pair));
469 		if (ret)
470 			return -EFAULT;
471 
472 		if (!riscv_hwprobe_key_is_valid(pair.key)) {
473 			clear_all = true;
474 			pair = (struct riscv_hwprobe){ .key = -1, };
475 			ret = copy_to_user(&pairs[i], &pair, sizeof(pair));
476 			if (ret)
477 				return -EFAULT;
478 		}
479 
480 		if (clear_all)
481 			continue;
482 
483 		tmp = (struct riscv_hwprobe){ .key = pair.key, };
484 
485 		for_each_cpu(cpu, &cpus) {
486 			cpumask_set_cpu(cpu, &one_cpu);
487 
488 			hwprobe_one_pair(&tmp, &one_cpu);
489 
490 			if (!riscv_hwprobe_pair_cmp(&tmp, &pair))
491 				cpumask_clear_cpu(cpu, &cpus);
492 
493 			cpumask_clear_cpu(cpu, &one_cpu);
494 		}
495 	}
496 
497 	if (clear_all)
498 		cpumask_clear(&cpus);
499 
500 	ret = copy_to_user(cpus_user, &cpus, cpusetsize);
501 	if (ret)
502 		return -EFAULT;
503 
504 	return 0;
505 }
506 
507 #ifdef CONFIG_MMU
508 
509 static DECLARE_COMPLETION(boot_probes_done);
510 static atomic_t pending_boot_probes = ATOMIC_INIT(1);
511 
riscv_hwprobe_register_async_probe(void)512 void riscv_hwprobe_register_async_probe(void)
513 {
514 	atomic_inc(&pending_boot_probes);
515 }
516 
riscv_hwprobe_complete_async_probe(void)517 void riscv_hwprobe_complete_async_probe(void)
518 {
519 	if (atomic_dec_and_test(&pending_boot_probes))
520 		complete(&boot_probes_done);
521 }
522 
complete_hwprobe_vdso_data(void)523 static int complete_hwprobe_vdso_data(void)
524 {
525 	struct vdso_arch_data *avd = vdso_k_arch_data;
526 	u64 id_bitsmash = 0;
527 	struct riscv_hwprobe pair;
528 	int key;
529 
530 	if (unlikely(!atomic_dec_and_test(&pending_boot_probes)))
531 		wait_for_completion(&boot_probes_done);
532 
533 	/*
534 	 * Initialize vDSO data with the answers for the "all CPUs" case, to
535 	 * save a syscall in the common case.
536 	 */
537 	for (key = 0; key <= RISCV_HWPROBE_MAX_KEY; key++) {
538 		pair.key = key;
539 		hwprobe_one_pair(&pair, cpu_online_mask);
540 
541 		WARN_ON_ONCE(pair.key < 0);
542 
543 		avd->all_cpu_hwprobe_values[key] = pair.value;
544 		/*
545 		 * Smash together the vendor, arch, and impl IDs to see if
546 		 * they're all 0 or any negative.
547 		 */
548 		if (key <= RISCV_HWPROBE_KEY_MIMPID)
549 			id_bitsmash |= pair.value;
550 	}
551 
552 	/*
553 	 * If the arch, vendor, and implementation ID are all the same across
554 	 * all harts, then assume all CPUs are the same, and allow the vDSO to
555 	 * answer queries for arbitrary masks. However if all values are 0 (not
556 	 * populated) or any value returns -1 (varies across CPUs), then the
557 	 * vDSO should defer to the kernel for exotic cpu masks.
558 	 */
559 	avd->homogeneous_cpus = id_bitsmash != 0 && id_bitsmash != -1;
560 
561 	/*
562 	 * Make sure all the VDSO values are visible before we look at them.
563 	 * This pairs with the implicit "no speculativly visible accesses"
564 	 * barrier in the VDSO hwprobe code.
565 	 */
566 	smp_wmb();
567 	avd->ready = true;
568 	return 0;
569 }
570 
init_hwprobe_vdso_data(void)571 static int __init init_hwprobe_vdso_data(void)
572 {
573 	struct vdso_arch_data *avd = vdso_k_arch_data;
574 
575 	/*
576 	 * Prevent the vDSO cached values from being used, as they're not ready
577 	 * yet.
578 	 */
579 	avd->ready = false;
580 	return 0;
581 }
582 
583 arch_initcall_sync(init_hwprobe_vdso_data);
584 
585 #else
586 
complete_hwprobe_vdso_data(void)587 static int complete_hwprobe_vdso_data(void) { return 0; }
588 
589 #endif /* CONFIG_MMU */
590 
do_riscv_hwprobe(struct riscv_hwprobe __user * pairs,size_t pair_count,size_t cpusetsize,unsigned long __user * cpus_user,unsigned int flags)591 static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
592 			    size_t pair_count, size_t cpusetsize,
593 			    unsigned long __user *cpus_user,
594 			    unsigned int flags)
595 {
596 	DO_ONCE_SLEEPABLE(complete_hwprobe_vdso_data);
597 
598 	if (flags & RISCV_HWPROBE_WHICH_CPUS)
599 		return hwprobe_get_cpus(pairs, pair_count, cpusetsize,
600 					cpus_user, flags);
601 
602 	return hwprobe_get_values(pairs, pair_count, cpusetsize,
603 				cpus_user, flags);
604 }
605 
SYSCALL_DEFINE5(riscv_hwprobe,struct riscv_hwprobe __user *,pairs,size_t,pair_count,size_t,cpusetsize,unsigned long __user *,cpus,unsigned int,flags)606 SYSCALL_DEFINE5(riscv_hwprobe, struct riscv_hwprobe __user *, pairs,
607 		size_t, pair_count, size_t, cpusetsize, unsigned long __user *,
608 		cpus, unsigned int, flags)
609 {
610 	return do_riscv_hwprobe(pairs, pair_count, cpusetsize,
611 				cpus, flags);
612 }
613