summaryrefslogtreecommitdiffstats
path: root/arch/x86/xen/p2m.c
blob: b3e11afed25bbbc3f6497240cef40a59b5cc12b6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
// SPDX-License-Identifier: GPL-2.0

/*
 * Xen leaves the responsibility for maintaining p2m mappings to the
 * guests themselves, but it must also access and update the p2m array
 * during suspend/resume when all the pages are reallocated.
 *
 * The logical flat p2m table is mapped to a linear kernel memory area.
 * For accesses by Xen a three-level tree linked via mfns only is set up to
 * allow the address space to be sparse.
 *
 *               Xen
 *                |
 *          p2m_top_mfn
 *              /   \
 * p2m_mid_mfn p2m_mid_mfn
 *         /           /
 *  p2m p2m p2m ...
 *
 * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
 *
 * The p2m_top_mfn level is limited to 1 page, so the maximum representable
 * pseudo-physical address space is:
 *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
 *
 * P2M_PER_PAGE depends on the architecture, as a mfn is always
 * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
 * 512 and 1024 entries respectively.
 *
 * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
 *
 * However not all entries are filled with MFNs. Specifically for all other
 * leaf entries, or for the top  root, or middle one, for which there is a void
 * entry, we assume it is  "missing". So (for example)
 *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
 * We have a dedicated page p2m_missing with all entries being
 * INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
 * list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
 *
 * We also have the possibility of setting 1-1 mappings on certain regions, so
 * that:
 *  pfn_to_mfn(0xc0000)=0xc0000
 *
 * The benefit of this is, that we can assume for non-RAM regions (think
 * PCI BARs, or ACPI spaces), we can create mappings easily because we
 * get the PFN value to match the MFN.
 *
 * For this to work efficiently we have one new page p2m_identity. All entries
 * in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
 * recognizes that and MFNs, no other fancy value).
 *
 * On lookup we spot that the entry points to p2m_identity and return the
 * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
 * If the entry points to an allocated page, we just proceed as before and
 * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
 * appropriate functions (pfn_to_mfn).
 *
 * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
 * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
 * non-identity pfn. To protect ourselves against we elect to set (and get) the
 * IDENTITY_FRAME_BIT on all identity mapped PFNs.
 */

#include <linux/init.h>
#include <linux/export.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/bootmem.h>
#include <linux/memblock.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include <asm/cache.h>
#include <asm/setup.h>
#include <linux/uaccess.h>

#include <asm/xen/page.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <xen/balloon.h>
#include <xen/grant_table.h>

#include "multicalls.h"
#include "xen-ops.h"

#define P2M_MID_PER_PAGE	(PAGE_SIZE / sizeof(unsigned long *))
#define P2M_TOP_PER_PAGE	(PAGE_SIZE / sizeof(unsigned long **))

#define MAX_P2M_PFN	(P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)

#define PMDS_PER_MID_PAGE	(P2M_MID_PER_PAGE / PTRS_PER_PTE)

unsigned long *xen_p2m_addr __read_mostly;
EXPORT_SYMBOL_GPL(xen_p2m_addr);
unsigned long xen_p2m_size __read_mostly;
EXPORT_SYMBOL_GPL(xen_p2m_size);
unsigned long xen_max_p2m_pfn __read_mostly;
EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);

#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
#define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
#else
#define P2M_LIMIT 0
#endif

static DEFINE_SPINLOCK(p2m_update_lock);

static unsigned long *p2m_mid_missing_mfn;
static unsigned long *p2m_top_mfn;
static unsigned long **p2m_top_mfn_p;
static unsigned long *p2m_missing;
static unsigned long *p2m_identity;
static pte_t *p2m_missing_pte;
static pte_t *p2m_identity_pte;

/*
 * Hint at last populated PFN.
 *
 * Used to set HYPERVISOR_shared_info->arch.max_pfn so the toolstack
 * can avoid scanning the whole P2M (which may be sized to account for
 * hotplugged memory).
 */
static unsigned long xen_p2m_last_pfn;

static inline unsigned p2m_top_index(unsigned long pfn)
{
	BUG_ON(pfn >= MAX_P2M_PFN);
	return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
}

static inline unsigned p2m_mid_index(unsigned long pfn)
{
	return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
}

static inline unsigned p2m_index(unsigned long pfn)
{
	return pfn % P2M_PER_PAGE;
}

static void p2m_top_mfn_init(unsigned long *top)
{
	unsigned i;

	for (i = 0; i < P2M_TOP_PER_PAGE; i++)
		top[i] = virt_to_mfn(p2m_mid_missing_mfn);
}

static void p2m_top_mfn_p_init(unsigned long **top)
{
	unsigned i;

	for (i = 0; i < P2M_TOP_PER_PAGE; i++)
		top[i] = p2m_mid_missing_mfn;
}

static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
{
	unsigned i;

	for (i = 0; i < P2M_MID_PER_PAGE; i++)
		mid[i] = virt_to_mfn(leaf);
}

static void p2m_init(unsigned long *p2m)
{
	unsigned i;

	for (i = 0; i < P2M_PER_PAGE; i++)
		p2m[i] = INVALID_P2M_ENTRY;
}

static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
{
	unsigned i;

	for (i = 0; i < P2M_PER_PAGE; i++)
		p2m[i] = IDENTITY_FRAME(pfn + i);
}

static void * __ref alloc_p2m_page(void)
{
	if (unlikely(!slab_is_available()))
		return memblock_alloc(PAGE_SIZE, PAGE_SIZE);

	return (void *)__get_free_page(GFP_KERNEL);
}

static void __ref free_p2m_page(void *p)
{
	if (unlikely(!slab_is_available())) {
		memblock_free((unsigned long)p, PAGE_SIZE);
		return;
	}

	free_page((unsigned long)p);
}

/*
 * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
 *
 * This is called both at boot time, and after resuming from suspend:
 * - At boot time we're called rather early, and must use alloc_bootmem*()
 *   to allocate memory.
 *
 * - After resume we're called from within stop_machine, but the mfn
 *   tree should already be completely allocated.
 */
void __ref xen_build_mfn_list_list(void)
{
	unsigned long pfn, mfn;
	pte_t *ptep;
	unsigned int level, topidx, mididx;
	unsigned long *mid_mfn_p;

	if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
		return;

	/* Pre-initialize p2m_top_mfn to be completely missing */
	if (p2m_top_mfn == NULL) {
		p2m_mid_missing_mfn = alloc_p2m_page();
		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);

		p2m_top_mfn_p = alloc_p2m_page();
		p2m_top_mfn_p_init(p2m_top_mfn_p);

		p2m_top_mfn = alloc_p2m_page();
		p2m_top_mfn_init(p2m_top_mfn);
	} else {
		/* Reinitialise, mfn's all change after migration */
		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
	}

	for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
	     pfn += P2M_PER_PAGE) {
		topidx = p2m_top_index(pfn);
		mididx = p2m_mid_index(pfn);

		mid_mfn_p = p2m_top_mfn_p[topidx];
		ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
				      &level);
		BUG_ON(!ptep || level != PG_LEVEL_4K);
		mfn = pte_mfn(*ptep);
		ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));

		/* Don't bother allocating any mfn mid levels if
		 * they're just missing, just update the stored mfn,
		 * since all could have changed over a migrate.
		 */
		if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
			BUG_ON(mididx);
			BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
			p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
			pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
			continue;
		}

		if (mid_mfn_p == p2m_mid_missing_mfn) {
			mid_mfn_p = alloc_p2m_page();
			p2m_mid_mfn_init(mid_mfn_p, p2m_missing);

			p2m_top_mfn_p[topidx] = mid_mfn_p;
		}

		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
		mid_mfn_p[mididx] = mfn;
	}
}

void xen_setup_mfn_list_list(void)
{
	BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);

	if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
		HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = ~0UL;
	else
		HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
			virt_to_mfn(p2m_top_mfn);
	HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
	HYPERVISOR_shared_info->arch.p2m_generation = 0;
	HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
	HYPERVISOR_shared_info->arch.p2m_cr3 =
		xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
}

/* Set up p2m_top to point to the domain-builder provided p2m pages */
void __init xen_build_dynamic_phys_to_machine(void)
{
	unsigned long pfn;

	xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
	xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);

	for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
		xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;

	xen_max_p2m_pfn = xen_p2m_size;
}

#define P2M_TYPE_IDENTITY	0
#define P2M_TYPE_MISSING	1
#define P2M_TYPE_PFN		2
#define P2M_TYPE_UNKNOWN	3

static int xen_p2m_elem_type(unsigned long pfn)
{
	unsigned long mfn;

	if (pfn >= xen_p2m_size)
		return P2M_TYPE_IDENTITY;

	mfn = xen_p2m_addr[pfn];

	if (mfn == INVALID_P2M_ENTRY)
		return P2M_TYPE_MISSING;

	if (mfn & IDENTITY_FRAME_BIT)
		return P2M_TYPE_IDENTITY;

	return P2M_TYPE_PFN;
}

static void __init xen_rebuild_p2m_list(unsigned long *p2m)
{
	unsigned int i, chunk;
	unsigned long pfn;
	unsigned long *mfns;
	pte_t *ptep;
	pmd_t *pmdp;
	int type;

	p2m_missing = alloc_p2m_page();
	p2m_init(p2m_missing);
	p2m_identity = alloc_p2m_page();
	p2m_init(p2m_identity);

	p2m_missing_pte = alloc_p2m_page();
	paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
	p2m_identity_pte = alloc_p2m_page();
	paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
	for (i = 0; i < PTRS_PER_PTE; i++) {
		set_pte(p2m_missing_pte + i,
			pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
		set_pte(p2m_identity_pte + i,
			pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
	}

	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
		/*
		 * Try to map missing/identity PMDs or p2m-pages if possible.
		 * We have to respect the structure of the mfn_list_list
		 * which will be built just afterwards.
		 * Chunk size to test is one p2m page if we are in the middle
		 * of a mfn_list_list mid page and the complete mid page area
		 * if we are at index 0 of the mid page. Please note that a
		 * mid page might cover more than one PMD, e.g. on 32 bit PAE
		 * kernels.
		 */
		chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
			P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;

		type = xen_p2m_elem_type(pfn);
		i = 0;
		if (type != P2M_TYPE_PFN)
			for (i = 1; i < chunk; i++)
				if (xen_p2m_elem_type(pfn + i) != type)
					break;
		if (i < chunk)
			/* Reset to minimal chunk size. */
			chunk = P2M_PER_PAGE;

		if (type == P2M_TYPE_PFN || i < chunk) {
			/* Use initial p2m page contents. */
#ifdef CONFIG_X86_64
			mfns = alloc_p2m_page();
			copy_page(mfns, xen_p2m_addr + pfn);
#else
			mfns = xen_p2m_addr + pfn;
#endif
			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
			set_pte(ptep,
				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
			continue;
		}

		if (chunk == P2M_PER_PAGE) {
			/* Map complete missing or identity p2m-page. */
			mfns = (type == P2M_TYPE_MISSING) ?
				p2m_missing : p2m_identity;
			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
			set_pte(ptep,
				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
			continue;
		}

		/* Complete missing or identity PMD(s) can be mapped. */
		ptep = (type == P2M_TYPE_MISSING) ?
			p2m_missing_pte : p2m_identity_pte;
		for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
			pmdp = populate_extra_pmd(
				(unsigned long)(p2m + pfn) + i * PMD_SIZE);
			set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
		}
	}
}

void __init xen_vmalloc_p2m_tree(void)
{
	static struct vm_struct vm;
	unsigned long p2m_limit;

	xen_p2m_last_pfn = xen_max_p2m_pfn;

	p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
	vm.flags = VM_ALLOC;
	vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
			PMD_SIZE * PMDS_PER_MID_PAGE);
	vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
	pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);

	xen_max_p2m_pfn = vm.size / sizeof(unsigned long);

	xen_rebuild_p2m_list(vm.addr);

	xen_p2m_addr = vm.addr;
	xen_p2m_size = xen_max_p2m_pfn;

	xen_inv_extra_mem();
}

unsigned long get_phys_to_machine(unsigned long pfn)
{
	pte_t *ptep;
	unsigned int level;

	if (unlikely(pfn >= xen_p2m_size)) {
		if (pfn < xen_max_p2m_pfn)
			return xen_chk_extra_mem(pfn);

		return IDENTITY_FRAME(pfn);
	}

	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
	BUG_ON(!ptep || level != PG_LEVEL_4K);

	/*
	 * The INVALID_P2M_ENTRY is filled in both p2m_*identity
	 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
	 * would be wrong.
	 */
	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
		return IDENTITY_FRAME(pfn);

	return xen_p2m_addr[pfn];
}
EXPORT_SYMBOL_GPL(get_phys_to_machine);

/*
 * Allocate new pmd(s). It is checked whether the old pmd is still in place.
 * If not, nothing is changed. This is okay as the only reason for allocating
 * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
 * pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
 */
static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
{
	pte_t *ptechk;
	pte_t *pte_newpg[PMDS_PER_MID_PAGE];
	pmd_t *pmdp;
	unsigned int level;
	unsigned long flags;
	unsigned long vaddr;
	int i;

	/* Do all allocations first to bail out in error case. */
	for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
		pte_newpg[i] = alloc_p2m_page();
		if (!pte_newpg[i]) {
			for (i--; i >= 0; i--)
				free_p2m_page(pte_newpg[i]);

			return NULL;
		}
	}

	vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);

	for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
		copy_page(pte_newpg[i], pte_pg);
		paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);

		pmdp = lookup_pmd_address(vaddr);
		BUG_ON(!pmdp);

		spin_lock_irqsave(&p2m_update_lock, flags);

		ptechk = lookup_address(vaddr, &level);
		if (ptechk == pte_pg) {
			HYPERVISOR_shared_info->arch.p2m_generation++;
			wmb(); /* Tools are synchronizing via p2m_generation. */
			set_pmd(pmdp,
				__pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
			wmb(); /* Tools are synchronizing via p2m_generation. */
			HYPERVISOR_shared_info->arch.p2m_generation++;
			pte_newpg[i] = NULL;
		}

		spin_unlock_irqrestore(&p2m_update_lock, flags);

		if (pte_newpg[i]) {
			paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
			free_p2m_page(pte_newpg[i]);
		}

		vaddr += PMD_SIZE;
	}

	return lookup_address(addr, &level);
}

/*
 * Fully allocate the p2m structure for a given pfn.  We need to check
 * that both the top and mid levels are allocated, and make sure the
 * parallel mfn tree is kept in sync.  We may race with other cpus, so
 * the new pages are installed with cmpxchg; if we lose the race then
 * simply free the page we allocated and use the one that's there.
 */
int xen_alloc_p2m_entry(unsigned long pfn)
{
	unsigned topidx;
	unsigned long *top_mfn_p, *mid_mfn;
	pte_t *ptep, *pte_pg;
	unsigned int level;
	unsigned long flags;
	unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
	unsigned long p2m_pfn;

	ptep = lookup_address(addr, &level);
	BUG_ON(!ptep || level != PG_LEVEL_4K);
	pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));

	if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
		/* PMD level is missing, allocate a new one */
		ptep = alloc_p2m_pmd(addr, pte_pg);
		if (!ptep)
			return -ENOMEM;
	}

	if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
		topidx = p2m_top_index(pfn);
		top_mfn_p = &p2m_top_mfn[topidx];
		mid_mfn = READ_ONCE(p2m_top_mfn_p[topidx]);

		BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);

		if (mid_mfn == p2m_mid_missing_mfn) {
			/* Separately check the mid mfn level */
			unsigned long missing_mfn;
			unsigned long mid_mfn_mfn;
			unsigned long old_mfn;

			mid_mfn = alloc_p2m_page();
			if (!mid_mfn)
				return -ENOMEM;

			p2m_mid_mfn_init(mid_mfn, p2m_missing);

			missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
			mid_mfn_mfn = virt_to_mfn(mid_mfn);
			old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
			if (old_mfn != missing_mfn) {
				free_p2m_page(mid_mfn);
				mid_mfn = mfn_to_virt(old_mfn);
			} else {
				p2m_top_mfn_p[topidx] = mid_mfn;
			}
		}
	} else {
		mid_mfn = NULL;
	}

	p2m_pfn = pte_pfn(READ_ONCE(*ptep));
	if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
	    p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
		/* p2m leaf page is missing */
		unsigned long *p2m;

		p2m = alloc_p2m_page();
		if (!p2m)
			return -ENOMEM;

		if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
			p2m_init(p2m);
		else
			p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));

		spin_lock_irqsave(&p2m_update_lock, flags);

		if (pte_pfn(*ptep) == p2m_pfn) {
			HYPERVISOR_shared_info->arch.p2m_generation++;
			wmb(); /* Tools are synchronizing via p2m_generation. */
			set_pte(ptep,
				pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
			wmb(); /* Tools are synchronizing via p2m_generation. */
			HYPERVISOR_shared_info->arch.p2m_generation++;
			if (mid_mfn)
				mid_mfn[p2m_mid_index(pfn)] = virt_to_mfn(p2m);
			p2m = NULL;
		}

		spin_unlock_irqrestore(&p2m_update_lock, flags);

		if (p2m)
			free_p2m_page(p2m);
	}

	/* Expanded the p2m? */
	if (pfn > xen_p2m_last_pfn) {
		xen_p2m_last_pfn = pfn;
		HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
	}

	return 0;
}
EXPORT_SYMBOL(xen_alloc_p2m_entry);

unsigned long __init set_phys_range_identity(unsigned long pfn_s,
				      unsigned long pfn_e)
{
	unsigned long pfn;

	if (unlikely(pfn_s >= xen_p2m_size))
		return 0;

	if (pfn_s > pfn_e)
		return 0;

	if (pfn_e > xen_p2m_size)
		pfn_e = xen_p2m_size;

	for (pfn = pfn_s; pfn < pfn_e; pfn++)
		xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);

	return pfn - pfn_s;
}

bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
	pte_t *ptep;
	unsigned int level;

	if (unlikely(pfn >= xen_p2m_size)) {
		BUG_ON(mfn != INVALID_P2M_ENTRY);
		return true;
	}

	/*
	 * The interface requires atomic updates on p2m elements.
	 * xen_safe_write_ulong() is using __put_user which does an atomic
	 * store via asm().
	 */
	if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
		return true;

	ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
	BUG_ON(!ptep || level != PG_LEVEL_4K);

	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
		return mfn == INVALID_P2M_ENTRY;

	if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
		return mfn == IDENTITY_FRAME(pfn);

	return false;
}

bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
	if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
		int ret;

		ret = xen_alloc_p2m_entry(pfn);
		if (ret < 0)
			return false;

		return __set_phys_to_machine(pfn, mfn);
	}

	return true;
}

int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
			    struct gnttab_map_grant_ref *kmap_ops,
			    struct page **pages, unsigned int count)
{
	int i, ret = 0;
	pte_t *pte;

	if (xen_feature(XENFEAT_auto_translated_physmap))
		return 0;

	if (kmap_ops) {
		ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
						kmap_ops, count);
		if (ret)
			goto out;
	}

	for (i = 0; i < count; i++) {
		unsigned long mfn, pfn;

		/* Do not add to override if the map failed. */
		if (map_ops[i].status)
			continue;

		if (map_ops[i].flags & GNTMAP_contains_pte) {
			pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
				(map_ops[i].host_addr & ~PAGE_MASK));
			mfn = pte_mfn(*pte);
		} else {
			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
		}
		pfn = page_to_pfn(pages[i]);

		WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned");

		if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
			ret = -ENOMEM;
			goto out;
		}
	}

out:
	return ret;
}
EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);

int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
			      struct gnttab_unmap_grant_ref *kunmap_ops,
			      struct page **pages, unsigned int count)
{
	int i, ret = 0;

	if (xen_feature(XENFEAT_auto_translated_physmap))
		return 0;

	for (i = 0; i < count; i++) {
		unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
		unsigned long pfn = page_to_pfn(pages[i]);

		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
			ret = -EINVAL;
			goto out;
		}

		set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
	}
	if (kunmap_ops)
		ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
						kunmap_ops, count);
out:
	return ret;
}
EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);

#ifdef CONFIG_XEN_DEBUG_FS
#include <linux/debugfs.h>
#include "debugfs.h"
static int p2m_dump_show(struct seq_file *m, void *v)
{
	static const char * const type_name[] = {
				[P2M_TYPE_IDENTITY] = "identity",
				[P2M_TYPE_MISSING] = "missing",
				[P2M_TYPE_PFN] = "pfn",
				[P2M_TYPE_UNKNOWN] = "abnormal"};
	unsigned long pfn, first_pfn;
	int type, prev_type;

	prev_type = xen_p2m_elem_type(0);
	first_pfn = 0;

	for (pfn = 0; pfn < xen_p2m_size; pfn++) {
		type = xen_p2m_elem_type(pfn);
		if (type != prev_type) {
			seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
				   type_name[prev_type]);
			prev_type = type;
			first_pfn = pfn;
		}
	}
	seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
		   type_name[prev_type]);
	return 0;
}

static int p2m_dump_open(struct inode *inode, struct file *filp)
{
	return single_open(filp, p2m_dump_show, NULL);
}

static const struct file_operations p2m_dump_fops = {
	.open		= p2m_dump_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static struct dentry *d_mmu_debug;

static int __init xen_p2m_debugfs(void)
{
	struct dentry *d_xen = xen_init_debugfs();

	if (d_xen == NULL)
		return -ENOMEM;

	d_mmu_debug = debugfs_create_dir("mmu", d_xen);

	debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
	return 0;
}
fs_initcall(xen_p2m_debugfs);
#endif /* CONFIG_XEN_DEBUG_FS */