xref: /freebsd/sys/x86/iommu/intel_utils.c (revision 0fcefb433d1265c4e6d4275eae7478cda1bf6a34)
1 /*-
2  * Copyright (c) 2013 The FreeBSD Foundation
3  * All rights reserved.
4  *
5  * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
6  * under sponsorship from the FreeBSD Foundation.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
32 
33 #include <sys/param.h>
34 #include <sys/bus.h>
35 #include <sys/kernel.h>
36 #include <sys/lock.h>
37 #include <sys/malloc.h>
38 #include <sys/memdesc.h>
39 #include <sys/mutex.h>
40 #include <sys/proc.h>
41 #include <sys/queue.h>
42 #include <sys/rman.h>
43 #include <sys/rwlock.h>
44 #include <sys/sched.h>
45 #include <sys/sf_buf.h>
46 #include <sys/sysctl.h>
47 #include <sys/systm.h>
48 #include <sys/taskqueue.h>
49 #include <sys/tree.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 <machine/bus.h>
58 #include <machine/cpu.h>
59 #include <x86/include/busdma_impl.h>
60 #include <x86/iommu/intel_reg.h>
61 #include <x86/iommu/busdma_dmar.h>
62 #include <x86/iommu/intel_dmar.h>
63 
64 u_int
65 dmar_nd2mask(u_int nd)
66 {
67 	static const u_int masks[] = {
68 		0x000f,	/* nd == 0 */
69 		0x002f,	/* nd == 1 */
70 		0x00ff,	/* nd == 2 */
71 		0x02ff,	/* nd == 3 */
72 		0x0fff,	/* nd == 4 */
73 		0x2fff,	/* nd == 5 */
74 		0xffff,	/* nd == 6 */
75 		0x0000,	/* nd == 7 reserved */
76 	};
77 
78 	KASSERT(nd <= 6, ("number of domains %d", nd));
79 	return (masks[nd]);
80 }
81 
82 static const struct sagaw_bits_tag {
83 	int agaw;
84 	int cap;
85 	int awlvl;
86 	int pglvl;
87 } sagaw_bits[] = {
88 	{.agaw = 30, .cap = DMAR_CAP_SAGAW_2LVL, .awlvl = DMAR_CTX2_AW_2LVL,
89 	    .pglvl = 2},
90 	{.agaw = 39, .cap = DMAR_CAP_SAGAW_3LVL, .awlvl = DMAR_CTX2_AW_3LVL,
91 	    .pglvl = 3},
92 	{.agaw = 48, .cap = DMAR_CAP_SAGAW_4LVL, .awlvl = DMAR_CTX2_AW_4LVL,
93 	    .pglvl = 4},
94 	{.agaw = 57, .cap = DMAR_CAP_SAGAW_5LVL, .awlvl = DMAR_CTX2_AW_5LVL,
95 	    .pglvl = 5},
96 	{.agaw = 64, .cap = DMAR_CAP_SAGAW_6LVL, .awlvl = DMAR_CTX2_AW_6LVL,
97 	    .pglvl = 6}
98 };
99 #define SIZEOF_SAGAW_BITS (sizeof(sagaw_bits) / sizeof(sagaw_bits[0]))
100 
101 bool
102 dmar_pglvl_supported(struct dmar_unit *unit, int pglvl)
103 {
104 	int i;
105 
106 	for (i = 0; i < SIZEOF_SAGAW_BITS; i++) {
107 		if (sagaw_bits[i].pglvl != pglvl)
108 			continue;
109 		if ((DMAR_CAP_SAGAW(unit->hw_cap) & sagaw_bits[i].cap) != 0)
110 			return (true);
111 	}
112 	return (false);
113 }
114 
115 int
116 ctx_set_agaw(struct dmar_ctx *ctx, int mgaw)
117 {
118 	int sagaw, i;
119 
120 	ctx->mgaw = mgaw;
121 	sagaw = DMAR_CAP_SAGAW(ctx->dmar->hw_cap);
122 	for (i = 0; i < SIZEOF_SAGAW_BITS; i++) {
123 		if (sagaw_bits[i].agaw >= mgaw) {
124 			ctx->agaw = sagaw_bits[i].agaw;
125 			ctx->pglvl = sagaw_bits[i].pglvl;
126 			ctx->awlvl = sagaw_bits[i].awlvl;
127 			return (0);
128 		}
129 	}
130 	device_printf(ctx->dmar->dev,
131 	    "context request mgaw %d for pci%d:%d:%d:%d, "
132 	    "no agaw found, sagaw %x\n", mgaw, ctx->dmar->segment, ctx->bus,
133 	     ctx->slot, ctx->func, sagaw);
134 	return (EINVAL);
135 }
136 
137 /*
138  * Find a best fit mgaw for the given maxaddr:
139  *   - if allow_less is false, must find sagaw which maps all requested
140  *     addresses (used by identity mappings);
141  *   - if allow_less is true, and no supported sagaw can map all requested
142  *     address space, accept the biggest sagaw, whatever is it.
143  */
144 int
145 dmar_maxaddr2mgaw(struct dmar_unit *unit, dmar_gaddr_t maxaddr, bool allow_less)
146 {
147 	int i;
148 
149 	for (i = 0; i < SIZEOF_SAGAW_BITS; i++) {
150 		if ((1ULL << sagaw_bits[i].agaw) >= maxaddr &&
151 		    (DMAR_CAP_SAGAW(unit->hw_cap) & sagaw_bits[i].cap) != 0)
152 			break;
153 	}
154 	if (allow_less && i == SIZEOF_SAGAW_BITS) {
155 		do {
156 			i--;
157 		} while ((DMAR_CAP_SAGAW(unit->hw_cap) & sagaw_bits[i].cap)
158 		    == 0);
159 	}
160 	if (i < SIZEOF_SAGAW_BITS)
161 		return (sagaw_bits[i].agaw);
162 	KASSERT(0, ("no mgaw for maxaddr %jx allow_less %d",
163 	    (uintmax_t) maxaddr, allow_less));
164 	return (-1);
165 }
166 
167 /*
168  * Calculate the total amount of page table pages needed to map the
169  * whole bus address space on the context with the selected agaw.
170  */
171 vm_pindex_t
172 pglvl_max_pages(int pglvl)
173 {
174 	vm_pindex_t res;
175 	int i;
176 
177 	for (res = 0, i = pglvl; i > 0; i--) {
178 		res *= DMAR_NPTEPG;
179 		res++;
180 	}
181 	return (res);
182 }
183 
184 /*
185  * Return true if the page table level lvl supports the superpage for
186  * the context ctx.
187  */
188 int
189 ctx_is_sp_lvl(struct dmar_ctx *ctx, int lvl)
190 {
191 	int alvl, cap_sps;
192 	static const int sagaw_sp[] = {
193 		DMAR_CAP_SPS_2M,
194 		DMAR_CAP_SPS_1G,
195 		DMAR_CAP_SPS_512G,
196 		DMAR_CAP_SPS_1T
197 	};
198 
199 	alvl = ctx->pglvl - lvl - 1;
200 	cap_sps = DMAR_CAP_SPS(ctx->dmar->hw_cap);
201 	return (alvl < sizeof(sagaw_sp) / sizeof(sagaw_sp[0]) &&
202 	    (sagaw_sp[alvl] & cap_sps) != 0);
203 }
204 
205 dmar_gaddr_t
206 pglvl_page_size(int total_pglvl, int lvl)
207 {
208 	int rlvl;
209 	static const dmar_gaddr_t pg_sz[] = {
210 		(dmar_gaddr_t)DMAR_PAGE_SIZE,
211 		(dmar_gaddr_t)DMAR_PAGE_SIZE << DMAR_NPTEPGSHIFT,
212 		(dmar_gaddr_t)DMAR_PAGE_SIZE << (2 * DMAR_NPTEPGSHIFT),
213 		(dmar_gaddr_t)DMAR_PAGE_SIZE << (3 * DMAR_NPTEPGSHIFT),
214 		(dmar_gaddr_t)DMAR_PAGE_SIZE << (4 * DMAR_NPTEPGSHIFT),
215 		(dmar_gaddr_t)DMAR_PAGE_SIZE << (5 * DMAR_NPTEPGSHIFT)
216 	};
217 
218 	KASSERT(lvl >= 0 && lvl < total_pglvl,
219 	    ("total %d lvl %d", total_pglvl, lvl));
220 	rlvl = total_pglvl - lvl - 1;
221 	KASSERT(rlvl < sizeof(pg_sz) / sizeof(pg_sz[0]),
222 	    ("sizeof pg_sz lvl %d", lvl));
223 	return (pg_sz[rlvl]);
224 }
225 
226 dmar_gaddr_t
227 ctx_page_size(struct dmar_ctx *ctx, int lvl)
228 {
229 
230 	return (pglvl_page_size(ctx->pglvl, lvl));
231 }
232 
233 int
234 calc_am(struct dmar_unit *unit, dmar_gaddr_t base, dmar_gaddr_t size,
235     dmar_gaddr_t *isizep)
236 {
237 	dmar_gaddr_t isize;
238 	int am;
239 
240 	for (am = DMAR_CAP_MAMV(unit->hw_cap);; am--) {
241 		isize = 1ULL << (am + DMAR_PAGE_SHIFT);
242 		if ((base & (isize - 1)) == 0 && size >= isize)
243 			break;
244 		if (am == 0)
245 			break;
246 	}
247 	*isizep = isize;
248 	return (am);
249 }
250 
251 dmar_haddr_t dmar_high;
252 int haw;
253 int dmar_tbl_pagecnt;
254 
255 vm_page_t
256 dmar_pgalloc(vm_object_t obj, vm_pindex_t idx, int flags)
257 {
258 	vm_page_t m;
259 	int zeroed;
260 
261 	zeroed = (flags & DMAR_PGF_ZERO) != 0 ? VM_ALLOC_ZERO : 0;
262 	for (;;) {
263 		if ((flags & DMAR_PGF_OBJL) == 0)
264 			VM_OBJECT_WLOCK(obj);
265 		m = vm_page_lookup(obj, idx);
266 		if ((flags & DMAR_PGF_NOALLOC) != 0 || m != NULL) {
267 			if ((flags & DMAR_PGF_OBJL) == 0)
268 				VM_OBJECT_WUNLOCK(obj);
269 			break;
270 		}
271 		m = vm_page_alloc_contig(obj, idx, VM_ALLOC_NOBUSY |
272 		    VM_ALLOC_SYSTEM | VM_ALLOC_NODUMP | zeroed, 1, 0,
273 		    dmar_high, PAGE_SIZE, 0, VM_MEMATTR_DEFAULT);
274 		if ((flags & DMAR_PGF_OBJL) == 0)
275 			VM_OBJECT_WUNLOCK(obj);
276 		if (m != NULL) {
277 			if (zeroed && (m->flags & PG_ZERO) == 0)
278 				pmap_zero_page(m);
279 			atomic_add_int(&dmar_tbl_pagecnt, 1);
280 			break;
281 		}
282 		if ((flags & DMAR_PGF_WAITOK) == 0)
283 			break;
284 		if ((flags & DMAR_PGF_OBJL) != 0)
285 			VM_OBJECT_WUNLOCK(obj);
286 		VM_WAIT;
287 		if ((flags & DMAR_PGF_OBJL) != 0)
288 			VM_OBJECT_WLOCK(obj);
289 	}
290 	return (m);
291 }
292 
293 void
294 dmar_pgfree(vm_object_t obj, vm_pindex_t idx, int flags)
295 {
296 	vm_page_t m;
297 
298 	if ((flags & DMAR_PGF_OBJL) == 0)
299 		VM_OBJECT_WLOCK(obj);
300 	m = vm_page_lookup(obj, idx);
301 	if (m != NULL) {
302 		vm_page_free(m);
303 		atomic_subtract_int(&dmar_tbl_pagecnt, 1);
304 	}
305 	if ((flags & DMAR_PGF_OBJL) == 0)
306 		VM_OBJECT_WUNLOCK(obj);
307 }
308 
309 void *
310 dmar_map_pgtbl(vm_object_t obj, vm_pindex_t idx, int flags,
311     struct sf_buf **sf)
312 {
313 	vm_page_t m;
314 	bool allocated;
315 
316 	if ((flags & DMAR_PGF_OBJL) == 0)
317 		VM_OBJECT_WLOCK(obj);
318 	m = vm_page_lookup(obj, idx);
319 	if (m == NULL && (flags & DMAR_PGF_ALLOC) != 0) {
320 		m = dmar_pgalloc(obj, idx, flags | DMAR_PGF_OBJL);
321 		allocated = true;
322 	} else
323 		allocated = false;
324 	if (m == NULL) {
325 		if ((flags & DMAR_PGF_OBJL) == 0)
326 			VM_OBJECT_WUNLOCK(obj);
327 		return (NULL);
328 	}
329 	/* Sleepable allocations cannot fail. */
330 	if ((flags & DMAR_PGF_WAITOK) != 0)
331 		VM_OBJECT_WUNLOCK(obj);
332 	sched_pin();
333 	*sf = sf_buf_alloc(m, SFB_CPUPRIVATE | ((flags & DMAR_PGF_WAITOK)
334 	    == 0 ? SFB_NOWAIT : 0));
335 	if (*sf == NULL) {
336 		sched_unpin();
337 		if (allocated) {
338 			VM_OBJECT_ASSERT_WLOCKED(obj);
339 			dmar_pgfree(obj, m->pindex, flags | DMAR_PGF_OBJL);
340 		}
341 		if ((flags & DMAR_PGF_OBJL) == 0)
342 			VM_OBJECT_WUNLOCK(obj);
343 		return (NULL);
344 	}
345 	if ((flags & (DMAR_PGF_WAITOK | DMAR_PGF_OBJL)) ==
346 	    (DMAR_PGF_WAITOK | DMAR_PGF_OBJL))
347 		VM_OBJECT_WLOCK(obj);
348 	else if ((flags & (DMAR_PGF_WAITOK | DMAR_PGF_OBJL)) == 0)
349 		VM_OBJECT_WUNLOCK(obj);
350 	return ((void *)sf_buf_kva(*sf));
351 }
352 
353 void
354 dmar_unmap_pgtbl(struct sf_buf *sf, bool coherent)
355 {
356 	vm_page_t m;
357 
358 	m = sf_buf_page(sf);
359 	sf_buf_free(sf);
360 	sched_unpin();
361 
362 	/*
363 	 * If DMAR does not snoop paging structures accesses, flush
364 	 * CPU cache to memory.
365 	 */
366 	if (!coherent)
367 		pmap_invalidate_cache_pages(&m, 1);
368 }
369 
370 /*
371  * Load the root entry pointer into the hardware, busily waiting for
372  * the completion.
373  */
374 int
375 dmar_load_root_entry_ptr(struct dmar_unit *unit)
376 {
377 	vm_page_t root_entry;
378 
379 	/*
380 	 * Access to the GCMD register must be serialized while the
381 	 * command is submitted.
382 	 */
383 	DMAR_ASSERT_LOCKED(unit);
384 
385 	/* VM_OBJECT_RLOCK(unit->ctx_obj); */
386 	VM_OBJECT_WLOCK(unit->ctx_obj);
387 	root_entry = vm_page_lookup(unit->ctx_obj, 0);
388 	/* VM_OBJECT_RUNLOCK(unit->ctx_obj); */
389 	VM_OBJECT_WUNLOCK(unit->ctx_obj);
390 	dmar_write8(unit, DMAR_RTADDR_REG, VM_PAGE_TO_PHYS(root_entry));
391 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd | DMAR_GCMD_SRTP);
392 	/* XXXKIB should have a timeout */
393 	while ((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_RTPS) == 0)
394 		cpu_spinwait();
395 	return (0);
396 }
397 
398 /*
399  * Globally invalidate the context entries cache, busily waiting for
400  * the completion.
401  */
402 int
403 dmar_inv_ctx_glob(struct dmar_unit *unit)
404 {
405 
406 	/*
407 	 * Access to the CCMD register must be serialized while the
408 	 * command is submitted.
409 	 */
410 	DMAR_ASSERT_LOCKED(unit);
411 	KASSERT(!unit->qi_enabled, ("QI enabled"));
412 
413 	/*
414 	 * The DMAR_CCMD_ICC bit in the upper dword should be written
415 	 * after the low dword write is completed.  Amd64
416 	 * dmar_write8() does not have this issue, i386 dmar_write8()
417 	 * writes the upper dword last.
418 	 */
419 	dmar_write8(unit, DMAR_CCMD_REG, DMAR_CCMD_ICC | DMAR_CCMD_CIRG_GLOB);
420 	/* XXXKIB should have a timeout */
421 	while ((dmar_read4(unit, DMAR_CCMD_REG + 4) & DMAR_CCMD_ICC32) != 0)
422 		cpu_spinwait();
423 	return (0);
424 }
425 
426 /*
427  * Globally invalidate the IOTLB, busily waiting for the completion.
428  */
429 int
430 dmar_inv_iotlb_glob(struct dmar_unit *unit)
431 {
432 	int reg;
433 
434 	DMAR_ASSERT_LOCKED(unit);
435 	KASSERT(!unit->qi_enabled, ("QI enabled"));
436 
437 	reg = 16 * DMAR_ECAP_IRO(unit->hw_ecap);
438 	/* See a comment about DMAR_CCMD_ICC in dmar_inv_ctx_glob. */
439 	dmar_write8(unit, reg + DMAR_IOTLB_REG_OFF, DMAR_IOTLB_IVT |
440 	    DMAR_IOTLB_IIRG_GLB | DMAR_IOTLB_DR | DMAR_IOTLB_DW);
441 	/* XXXKIB should have a timeout */
442 	while ((dmar_read4(unit, reg + DMAR_IOTLB_REG_OFF + 4) &
443 	    DMAR_IOTLB_IVT32) != 0)
444 		cpu_spinwait();
445 	return (0);
446 }
447 
448 /*
449  * Flush the chipset write buffers.  See 11.1 "Write Buffer Flushing"
450  * in the architecture specification.
451  */
452 int
453 dmar_flush_write_bufs(struct dmar_unit *unit)
454 {
455 
456 	DMAR_ASSERT_LOCKED(unit);
457 
458 	/*
459 	 * DMAR_GCMD_WBF is only valid when CAP_RWBF is reported.
460 	 */
461 	KASSERT((unit->hw_cap & DMAR_CAP_RWBF) != 0,
462 	    ("dmar%d: no RWBF", unit->unit));
463 
464 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd | DMAR_GCMD_WBF);
465 	/* XXXKIB should have a timeout */
466 	while ((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_WBFS) == 0)
467 		cpu_spinwait();
468 	return (0);
469 }
470 
471 int
472 dmar_enable_translation(struct dmar_unit *unit)
473 {
474 
475 	DMAR_ASSERT_LOCKED(unit);
476 	unit->hw_gcmd |= DMAR_GCMD_TE;
477 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd);
478 	/* XXXKIB should have a timeout */
479 	while ((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_TES) == 0)
480 		cpu_spinwait();
481 	return (0);
482 }
483 
484 int
485 dmar_disable_translation(struct dmar_unit *unit)
486 {
487 
488 	DMAR_ASSERT_LOCKED(unit);
489 	unit->hw_gcmd &= ~DMAR_GCMD_TE;
490 	dmar_write4(unit, DMAR_GCMD_REG, unit->hw_gcmd);
491 	/* XXXKIB should have a timeout */
492 	while ((dmar_read4(unit, DMAR_GSTS_REG) & DMAR_GSTS_TES) != 0)
493 		cpu_spinwait();
494 	return (0);
495 }
496 
497 #define BARRIER_F				\
498 	u_int f_done, f_inproc, f_wakeup;	\
499 						\
500 	f_done = 1 << (barrier_id * 3);		\
501 	f_inproc = 1 << (barrier_id * 3 + 1);	\
502 	f_wakeup = 1 << (barrier_id * 3 + 2)
503 
504 bool
505 dmar_barrier_enter(struct dmar_unit *dmar, u_int barrier_id)
506 {
507 	BARRIER_F;
508 
509 	DMAR_LOCK(dmar);
510 	if ((dmar->barrier_flags & f_done) != 0) {
511 		DMAR_UNLOCK(dmar);
512 		return (false);
513 	}
514 
515 	if ((dmar->barrier_flags & f_inproc) != 0) {
516 		while ((dmar->barrier_flags & f_inproc) != 0) {
517 			dmar->barrier_flags |= f_wakeup;
518 			msleep(&dmar->barrier_flags, &dmar->lock, 0,
519 			    "dmarb", 0);
520 		}
521 		KASSERT((dmar->barrier_flags & f_done) != 0,
522 		    ("dmar%d barrier %d missing done", dmar->unit, 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->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_match_verbose;
548 
549 static SYSCTL_NODE(_hw, OID_AUTO, dmar, CTLFLAG_RD, NULL,
550     "");
551 SYSCTL_INT(_hw_dmar, OID_AUTO, tbl_pagecnt, CTLFLAG_RD | CTLFLAG_TUN,
552     &dmar_tbl_pagecnt, 0,
553     "Count of pages used for DMAR pagetables");
554 SYSCTL_INT(_hw_dmar, OID_AUTO, match_verbose, CTLFLAG_RW | CTLFLAG_TUN,
555     &dmar_match_verbose, 0,
556     "Verbose matching of the PCI devices to DMAR paths");
557 #ifdef INVARIANTS
558 int dmar_check_free;
559 SYSCTL_INT(_hw_dmar, OID_AUTO, check_free, CTLFLAG_RW | CTLFLAG_TUN,
560     &dmar_check_free, 0,
561     "Check the GPA RBtree for free_down and free_after validity");
562 #endif
563 
564