xref: /freebsd/sys/x86/iommu/intel_utils.c (revision c57c26179033f64c2011a2d2a904ee3fa62e826a)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2013 The FreeBSD Foundation
5  *
6  * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
7  * under sponsorship from the FreeBSD Foundation.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGE.
29  */
30 
31 #include <sys/param.h>
32 #include <sys/bus.h>
33 #include <sys/kernel.h>
34 #include <sys/lock.h>
35 #include <sys/malloc.h>
36 #include <sys/memdesc.h>
37 #include <sys/mutex.h>
38 #include <sys/proc.h>
39 #include <sys/queue.h>
40 #include <sys/rman.h>
41 #include <sys/rwlock.h>
42 #include <sys/sched.h>
43 #include <sys/sf_buf.h>
44 #include <sys/sysctl.h>
45 #include <sys/systm.h>
46 #include <sys/taskqueue.h>
47 #include <sys/time.h>
48 #include <sys/tree.h>
49 #include <sys/vmem.h>
50 #include <vm/vm.h>
51 #include <vm/vm_extern.h>
52 #include <vm/vm_kern.h>
53 #include <vm/vm_object.h>
54 #include <vm/vm_page.h>
55 #include <vm/vm_map.h>
56 #include <vm/vm_pageout.h>
57 #include <dev/pci/pcireg.h>
58 #include <dev/pci/pcivar.h>
59 #include <machine/bus.h>
60 #include <machine/cpu.h>
61 #include <machine/intr_machdep.h>
62 #include <x86/include/apicvar.h>
63 #include <x86/include/busdma_impl.h>
64 #include <dev/iommu/busdma_iommu.h>
65 #include <x86/iommu/intel_reg.h>
66 #include <x86/iommu/x86_iommu.h>
67 #include <x86/iommu/intel_dmar.h>
68 
69 u_int
70 dmar_nd2mask(u_int nd)
71 {
72 	static const u_int masks[] = {
73 		0x000f,	/* nd == 0 */
74 		0x002f,	/* nd == 1 */
75 		0x00ff,	/* nd == 2 */
76 		0x02ff,	/* nd == 3 */
77 		0x0fff,	/* nd == 4 */
78 		0x2fff,	/* nd == 5 */
79 		0xffff,	/* nd == 6 */
80 		0x0000,	/* nd == 7 reserved */
81 	};
82 
83 	KASSERT(nd <= 6, ("number of domains %d", nd));
84 	return (masks[nd]);
85 }
86 
87 static const struct sagaw_bits_tag {
88 	int agaw;
89 	int cap;
90 	int awlvl;
91 	int pglvl;
92 } sagaw_bits[] = {
93 	{.agaw = 30, .cap = DMAR_CAP_SAGAW_2LVL, .awlvl = DMAR_CTX2_AW_2LVL,
94 	    .pglvl = 2},
95 	{.agaw = 39, .cap = DMAR_CAP_SAGAW_3LVL, .awlvl = DMAR_CTX2_AW_3LVL,
96 	    .pglvl = 3},
97 	{.agaw = 48, .cap = DMAR_CAP_SAGAW_4LVL, .awlvl = DMAR_CTX2_AW_4LVL,
98 	    .pglvl = 4},
99 	{.agaw = 57, .cap = DMAR_CAP_SAGAW_5LVL, .awlvl = DMAR_CTX2_AW_5LVL,
100 	    .pglvl = 5}
101 	/*
102 	 * 6-level paging (DMAR_CAP_SAGAW_6LVL) is not supported on any
103 	 * current VT-d hardware and its SAGAW field value is listed as
104 	 * reserved in the VT-d spec.  If support is added in the future,
105 	 * this structure and the logic in dmar_maxaddr2mgaw() will need
106 	 * to change to avoid attempted comparison against 1ULL << 64.
107 	 */
108 };
109 
110 bool
111 dmar_pglvl_supported(struct dmar_unit *unit, int pglvl)
112 {
113 	int i;
114 
115 	for (i = 0; i < nitems(sagaw_bits); i++) {
116 		if (sagaw_bits[i].pglvl != pglvl)
117 			continue;
118 		if ((DMAR_CAP_SAGAW(unit->hw_cap) & sagaw_bits[i].cap) != 0)
119 			return (true);
120 	}
121 	return (false);
122 }
123 
124 int
125 domain_set_agaw(struct dmar_domain *domain, int mgaw)
126 {
127 	int sagaw, i;
128 
129 	domain->mgaw = mgaw;
130 	sagaw = DMAR_CAP_SAGAW(domain->dmar->hw_cap);
131 	for (i = 0; i < nitems(sagaw_bits); i++) {
132 		if (sagaw_bits[i].agaw >= mgaw) {
133 			domain->agaw = sagaw_bits[i].agaw;
134 			domain->pglvl = sagaw_bits[i].pglvl;
135 			domain->awlvl = sagaw_bits[i].awlvl;
136 			return (0);
137 		}
138 	}
139 	device_printf(domain->dmar->iommu.dev,
140 	    "context request mgaw %d: no agaw found, sagaw %x\n",
141 	    mgaw, sagaw);
142 	return (EINVAL);
143 }
144 
145 /*
146  * Find a best fit mgaw for the given maxaddr:
147  *   - if allow_less is false, must find sagaw which maps all requested
148  *     addresses (used by identity mappings);
149  *   - if allow_less is true, and no supported sagaw can map all requested
150  *     address space, accept the biggest sagaw, whatever is it.
151  */
152 int
153 dmar_maxaddr2mgaw(struct dmar_unit *unit, iommu_gaddr_t maxaddr, bool allow_less)
154 {
155 	int i;
156 
157 	for (i = 0; i < nitems(sagaw_bits); i++) {
158 		if ((1ULL << sagaw_bits[i].agaw) >= maxaddr &&
159 		    (DMAR_CAP_SAGAW(unit->hw_cap) & sagaw_bits[i].cap) != 0)
160 			break;
161 	}
162 	if (allow_less && i == nitems(sagaw_bits)) {
163 		do {
164 			i--;
165 		} while ((DMAR_CAP_SAGAW(unit->hw_cap) & sagaw_bits[i].cap)
166 		    == 0);
167 	}
168 	if (i < nitems(sagaw_bits))
169 		return (sagaw_bits[i].agaw);
170 	KASSERT(0, ("no mgaw for maxaddr %jx allow_less %d",
171 	    (uintmax_t) maxaddr, allow_less));
172 	return (-1);
173 }
174 
175 /*
176  * Calculate the total amount of page table pages needed to map the
177  * whole bus address space on the context with the selected agaw.
178  */
179 vm_pindex_t
180 pglvl_max_pages(int pglvl)
181 {
182 	vm_pindex_t res;
183 	int i;
184 
185 	for (res = 0, i = pglvl; i > 0; i--) {
186 		res *= IOMMU_NPTEPG;
187 		res++;
188 	}
189 	return (res);
190 }
191 
192 /*
193  * Return true if the page table level lvl supports the superpage for
194  * the context ctx.
195  */
196 int
197 domain_is_sp_lvl(struct dmar_domain *domain, int lvl)
198 {
199 	int alvl, cap_sps;
200 	static const int sagaw_sp[] = {
201 		DMAR_CAP_SPS_2M,
202 		DMAR_CAP_SPS_1G,
203 		DMAR_CAP_SPS_512G,
204 		DMAR_CAP_SPS_1T
205 	};
206 
207 	alvl = domain->pglvl - lvl - 1;
208 	cap_sps = DMAR_CAP_SPS(domain->dmar->hw_cap);
209 	return (alvl < nitems(sagaw_sp) && (sagaw_sp[alvl] & cap_sps) != 0);
210 }
211 
212 iommu_gaddr_t
213 pglvl_page_size(int total_pglvl, int lvl)
214 {
215 	int rlvl;
216 	static const iommu_gaddr_t pg_sz[] = {
217 		(iommu_gaddr_t)IOMMU_PAGE_SIZE,
218 		(iommu_gaddr_t)IOMMU_PAGE_SIZE << IOMMU_NPTEPGSHIFT,
219 		(iommu_gaddr_t)IOMMU_PAGE_SIZE << (2 * IOMMU_NPTEPGSHIFT),
220 		(iommu_gaddr_t)IOMMU_PAGE_SIZE << (3 * IOMMU_NPTEPGSHIFT),
221 		(iommu_gaddr_t)IOMMU_PAGE_SIZE << (4 * IOMMU_NPTEPGSHIFT),
222 		(iommu_gaddr_t)IOMMU_PAGE_SIZE << (5 * IOMMU_NPTEPGSHIFT),
223 	};
224 
225 	KASSERT(lvl >= 0 && lvl < total_pglvl,
226 	    ("total %d lvl %d", total_pglvl, lvl));
227 	rlvl = total_pglvl - lvl - 1;
228 	KASSERT(rlvl < nitems(pg_sz), ("sizeof pg_sz lvl %d", lvl));
229 	return (pg_sz[rlvl]);
230 }
231 
232 iommu_gaddr_t
233 domain_page_size(struct dmar_domain *domain, int lvl)
234 {
235 
236 	return (pglvl_page_size(domain->pglvl, lvl));
237 }
238 
239 int
240 calc_am(struct dmar_unit *unit, iommu_gaddr_t base, iommu_gaddr_t size,
241     iommu_gaddr_t *isizep)
242 {
243 	iommu_gaddr_t isize;
244 	int am;
245 
246 	for (am = DMAR_CAP_MAMV(unit->hw_cap);; am--) {
247 		isize = 1ULL << (am + IOMMU_PAGE_SHIFT);
248 		if ((base & (isize - 1)) == 0 && size >= isize)
249 			break;
250 		if (am == 0)
251 			break;
252 	}
253 	*isizep = isize;
254 	return (am);
255 }
256 
257 int haw;
258 int dmar_tbl_pagecnt;
259 
260 static void
261 dmar_flush_transl_to_ram(struct dmar_unit *unit, void *dst, size_t sz)
262 {
263 
264 	if (DMAR_IS_COHERENT(unit))
265 		return;
266 	/*
267 	 * If DMAR does not snoop paging structures accesses, flush
268 	 * CPU cache to memory.
269 	 */
270 	pmap_force_invalidate_cache_range((uintptr_t)dst, (uintptr_t)dst + sz);
271 }
272 
273 void
274 dmar_flush_pte_to_ram(struct dmar_unit *unit, iommu_pte_t *dst)
275 {
276 
277 	dmar_flush_transl_to_ram(unit, dst, sizeof(*dst));
278 }
279 
280 void
281 dmar_flush_ctx_to_ram(struct dmar_unit *unit, dmar_ctx_entry_t *dst)
282 {
283 
284 	dmar_flush_transl_to_ram(unit, dst, sizeof(*dst));
285 }
286 
287 void
288 dmar_flush_root_to_ram(struct dmar_unit *unit, dmar_root_entry_t *dst)
289 {
290 
291 	dmar_flush_transl_to_ram(unit, dst, sizeof(*dst));
292 }
293 
294 /*
295  * Load the root entry pointer into the hardware, busily waiting for
296  * the completion.
297  */
298 int
299 dmar_load_root_entry_ptr(struct dmar_unit *unit)
300 {
301 	vm_page_t root_entry;
302 	int error;
303 
304 	/*
305 	 * Access to the GCMD register must be serialized while the
306 	 * command is submitted.
307 	 */
308 	DMAR_ASSERT_LOCKED(unit);
309 
310 	VM_OBJECT_RLOCK(unit->ctx_obj);
311 	root_entry = vm_page_lookup(unit->ctx_obj, 0);
312 	VM_OBJECT_RUNLOCK(unit->ctx_obj);
313 	dmar_write8(unit, DMAR_RTADDR_REG, VM_PAGE_TO_PHYS(root_entry));
314 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd | DMAR_GCMD_SRTP);
315 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_RTPS)
316 	    != 0));
317 	return (error);
318 }
319 
320 /*
321  * Globally invalidate the context entries cache, busily waiting for
322  * the completion.
323  */
324 int
325 dmar_inv_ctx_glob(struct dmar_unit *unit)
326 {
327 	int error;
328 
329 	/*
330 	 * Access to the CCMD register must be serialized while the
331 	 * command is submitted.
332 	 */
333 	DMAR_ASSERT_LOCKED(unit);
334 	KASSERT(!unit->qi_enabled, ("QI enabled"));
335 
336 	/*
337 	 * The DMAR_CCMD_ICC bit in the upper dword should be written
338 	 * after the low dword write is completed.  Amd64
339 	 * dmar_write8() does not have this issue, i386 dmar_write8()
340 	 * writes the upper dword last.
341 	 */
342 	dmar_write8(unit, DMAR_CCMD_REG, DMAR_CCMD_ICC | DMAR_CCMD_CIRG_GLOB);
343 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_CCMD_REG + 4) & DMAR_CCMD_ICC32)
344 	    == 0));
345 	return (error);
346 }
347 
348 /*
349  * Globally invalidate the IOTLB, busily waiting for the completion.
350  */
351 int
352 dmar_inv_iotlb_glob(struct dmar_unit *unit)
353 {
354 	int error, reg;
355 
356 	DMAR_ASSERT_LOCKED(unit);
357 	KASSERT(!unit->qi_enabled, ("QI enabled"));
358 
359 	reg = 16 * DMAR_ECAP_IRO(unit->hw_ecap);
360 	/* See a comment about DMAR_CCMD_ICC in dmar_inv_ctx_glob. */
361 	dmar_write8(unit, reg + DMAR_IOTLB_REG_OFF, DMAR_IOTLB_IVT |
362 	    DMAR_IOTLB_IIRG_GLB | DMAR_IOTLB_DR | DMAR_IOTLB_DW);
363 	DMAR_WAIT_UNTIL(((dmar_read4(unit, reg + DMAR_IOTLB_REG_OFF + 4) &
364 	    DMAR_IOTLB_IVT32) == 0));
365 	return (error);
366 }
367 
368 /*
369  * Flush the chipset write buffers.  See 11.1 "Write Buffer Flushing"
370  * in the architecture specification.
371  */
372 int
373 dmar_flush_write_bufs(struct dmar_unit *unit)
374 {
375 	int error;
376 
377 	DMAR_ASSERT_LOCKED(unit);
378 
379 	/*
380 	 * DMAR_GCMD_WBF is only valid when CAP_RWBF is reported.
381 	 */
382 	KASSERT((unit->hw_cap & DMAR_CAP_RWBF) != 0,
383 	    ("dmar%d: no RWBF", unit->iommu.unit));
384 
385 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd | DMAR_GCMD_WBF);
386 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_WBFS)
387 	    != 0));
388 	return (error);
389 }
390 
391 /*
392  * Some BIOSes protect memory region they reside in by using DMAR to
393  * prevent devices from doing any DMA transactions to that part of RAM.
394  * AMI refers to this as "DMA Control Guarantee".
395  * We need to disable this when address translation is enabled.
396  */
397 int
398 dmar_disable_protected_regions(struct dmar_unit *unit)
399 {
400 	uint32_t reg;
401 	int error;
402 
403 	DMAR_ASSERT_LOCKED(unit);
404 
405 	/* Check if we support the feature. */
406 	if ((unit->hw_cap & (DMAR_CAP_PLMR | DMAR_CAP_PHMR)) == 0)
407 		return (0);
408 
409 	reg = dmar_read4(unit, DMAR_PMEN_REG);
410 	if ((reg & DMAR_PMEN_EPM) == 0)
411 		return (0);
412 
413 	reg &= ~DMAR_PMEN_EPM;
414 	dmar_write4(unit, DMAR_PMEN_REG, reg);
415 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_PMEN_REG) & DMAR_PMEN_PRS)
416 	    != 0));
417 
418 	return (error);
419 }
420 
421 int
422 dmar_enable_translation(struct dmar_unit *unit)
423 {
424 	int error;
425 
426 	DMAR_ASSERT_LOCKED(unit);
427 	unit->hw_gcmd |= DMAR_GCMD_TE;
428 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd);
429 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_TES)
430 	    != 0));
431 	return (error);
432 }
433 
434 int
435 dmar_disable_translation(struct dmar_unit *unit)
436 {
437 	int error;
438 
439 	DMAR_ASSERT_LOCKED(unit);
440 	unit->hw_gcmd &= ~DMAR_GCMD_TE;
441 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd);
442 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_TES)
443 	    == 0));
444 	return (error);
445 }
446 
447 int
448 dmar_load_irt_ptr(struct dmar_unit *unit)
449 {
450 	uint64_t irta, s;
451 	int error;
452 
453 	DMAR_ASSERT_LOCKED(unit);
454 	irta = unit->irt_phys;
455 	if (DMAR_X2APIC(unit))
456 		irta |= DMAR_IRTA_EIME;
457 	s = fls(unit->irte_cnt) - 2;
458 	KASSERT(unit->irte_cnt >= 2 && s <= DMAR_IRTA_S_MASK &&
459 	    powerof2(unit->irte_cnt),
460 	    ("IRTA_REG_S overflow %x", unit->irte_cnt));
461 	irta |= s;
462 	dmar_write8(unit, DMAR_IRTA_REG, irta);
463 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd | DMAR_GCMD_SIRTP);
464 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_IRTPS)
465 	    != 0));
466 	return (error);
467 }
468 
469 int
470 dmar_enable_ir(struct dmar_unit *unit)
471 {
472 	int error;
473 
474 	DMAR_ASSERT_LOCKED(unit);
475 	unit->hw_gcmd |= DMAR_GCMD_IRE;
476 	unit->hw_gcmd &= ~DMAR_GCMD_CFI;
477 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd);
478 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_IRES)
479 	    != 0));
480 	return (error);
481 }
482 
483 int
484 dmar_disable_ir(struct dmar_unit *unit)
485 {
486 	int error;
487 
488 	DMAR_ASSERT_LOCKED(unit);
489 	unit->hw_gcmd &= ~DMAR_GCMD_IRE;
490 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd);
491 	DMAR_WAIT_UNTIL(((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_IRES)
492 	    == 0));
493 	return (error);
494 }
495 
496 #define BARRIER_F				\
497 	u_int f_done, f_inproc, f_wakeup;	\
498 						\
499 	f_done = 1 << (barrier_id * 3);		\
500 	f_inproc = 1 << (barrier_id * 3 + 1);	\
501 	f_wakeup = 1 << (barrier_id * 3 + 2)
502 
503 bool
504 dmar_barrier_enter(struct dmar_unit *dmar, u_int barrier_id)
505 {
506 	BARRIER_F;
507 
508 	DMAR_LOCK(dmar);
509 	if ((dmar->barrier_flags & f_done) != 0) {
510 		DMAR_UNLOCK(dmar);
511 		return (false);
512 	}
513 
514 	if ((dmar->barrier_flags & f_inproc) != 0) {
515 		while ((dmar->barrier_flags & f_inproc) != 0) {
516 			dmar->barrier_flags |= f_wakeup;
517 			msleep(&dmar->barrier_flags, &dmar->iommu.lock, 0,
518 			    "dmarb", 0);
519 		}
520 		KASSERT((dmar->barrier_flags & f_done) != 0,
521 		    ("dmar%d barrier %d missing done", dmar->iommu.unit,
522 		    barrier_id));
523 		DMAR_UNLOCK(dmar);
524 		return (false);
525 	}
526 
527 	dmar->barrier_flags |= f_inproc;
528 	DMAR_UNLOCK(dmar);
529 	return (true);
530 }
531 
532 void
533 dmar_barrier_exit(struct dmar_unit *dmar, u_int barrier_id)
534 {
535 	BARRIER_F;
536 
537 	DMAR_ASSERT_LOCKED(dmar);
538 	KASSERT((dmar->barrier_flags & (f_done | f_inproc)) == f_inproc,
539 	    ("dmar%d barrier %d missed entry", dmar->iommu.unit, barrier_id));
540 	dmar->barrier_flags |= f_done;
541 	if ((dmar->barrier_flags & f_wakeup) != 0)
542 		wakeup(&dmar->barrier_flags);
543 	dmar->barrier_flags &= ~(f_inproc | f_wakeup);
544 	DMAR_UNLOCK(dmar);
545 }
546 
547 int dmar_batch_coalesce = 100;
548 struct timespec dmar_hw_timeout = {
549 	.tv_sec = 0,
550 	.tv_nsec = 1000000
551 };
552 
553 static const uint64_t d = 1000000000;
554 
555 void
556 dmar_update_timeout(uint64_t newval)
557 {
558 
559 	/* XXXKIB not atomic */
560 	dmar_hw_timeout.tv_sec = newval / d;
561 	dmar_hw_timeout.tv_nsec = newval % d;
562 }
563 
564 uint64_t
565 dmar_get_timeout(void)
566 {
567 
568 	return ((uint64_t)dmar_hw_timeout.tv_sec * d +
569 	    dmar_hw_timeout.tv_nsec);
570 }
571 
572 static int
573 dmar_timeout_sysctl(SYSCTL_HANDLER_ARGS)
574 {
575 	uint64_t val;
576 	int error;
577 
578 	val = dmar_get_timeout();
579 	error = sysctl_handle_long(oidp, &val, 0, req);
580 	if (error != 0 || req->newptr == NULL)
581 		return (error);
582 	dmar_update_timeout(val);
583 	return (error);
584 }
585 
586 SYSCTL_INT(_hw_iommu_dmar, OID_AUTO, batch_coalesce, CTLFLAG_RWTUN,
587     &dmar_batch_coalesce, 0,
588     "Number of qi batches between interrupt");
589 SYSCTL_PROC(_hw_iommu_dmar, OID_AUTO, timeout,
590     CTLTYPE_U64 | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
591     dmar_timeout_sysctl, "QU",
592     "Timeout for command wait, in nanoseconds");
593