aboutsummaryrefslogtreecommitdiffstats
path: root/arch/x86/mm/pat.c
blob: e7ca7fc48d123d723be9e3efef3e63b1c34b74ba (plain) (blame)
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
/*
 * Handle caching attributes in page tables (PAT)
 *
 * Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *          Suresh B Siddha <suresh.b.siddha@intel.com>
 *
 * Loosely based on earlier PAT patchset from Eric Biederman and Andi Kleen.
 */

#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/gfp.h>
#include <linux/fs.h>
#include <linux/bootmem.h>

#include <asm/msr.h>
#include <asm/tlbflush.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/pat.h>
#include <asm/e820.h>
#include <asm/cacheflush.h>
#include <asm/fcntl.h>
#include <asm/mtrr.h>
#include <asm/io.h>

int pat_wc_enabled = 1;

static u64 __read_mostly boot_pat_state;

static int nopat(char *str)
{
	pat_wc_enabled = 0;
	printk(KERN_INFO "x86: PAT support disabled.\n");

	return 0;
}
early_param("nopat", nopat);

static int pat_known_cpu(void)
{
	if (!pat_wc_enabled)
		return 0;

	if (cpu_has_pat)
		return 1;

	pat_wc_enabled = 0;
	printk(KERN_INFO "CPU and/or kernel does not support PAT.\n");
	return 0;
}

enum {
	PAT_UC = 0,		/* uncached */
	PAT_WC = 1,		/* Write combining */
	PAT_WT = 4,		/* Write Through */
	PAT_WP = 5,		/* Write Protected */
	PAT_WB = 6,		/* Write Back (default) */
	PAT_UC_MINUS = 7,	/* UC, but can be overriden by MTRR */
};

#define PAT(x,y)	((u64)PAT_ ## y << ((x)*8))

void pat_init(void)
{
	u64 pat;

#ifndef CONFIG_X86_PAT
	nopat(NULL);
#endif

	/* Boot CPU enables PAT based on CPU feature */
	if (!smp_processor_id() && !pat_known_cpu())
		return;

	/* APs enable PAT iff boot CPU has enabled it before */
	if (smp_processor_id() && !pat_wc_enabled)
		return;

	/* Set PWT to Write-Combining. All other bits stay the same */
	/*
	 * PTE encoding used in Linux:
	 *      PAT
	 *      |PCD
	 *      ||PWT
	 *      |||
	 *      000 WB		_PAGE_CACHE_WB
	 *      001 WC		_PAGE_CACHE_WC
	 *      010 UC-		_PAGE_CACHE_UC_MINUS
	 *      011 UC		_PAGE_CACHE_UC
	 * PAT bit unused
	 */
	pat = PAT(0,WB) | PAT(1,WC) | PAT(2,UC_MINUS) | PAT(3,UC) |
	      PAT(4,WB) | PAT(5,WC) | PAT(6,UC_MINUS) | PAT(7,UC);

	/* Boot CPU check */
	if (!smp_processor_id()) {
		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
	}

	wrmsrl(MSR_IA32_CR_PAT, pat);
	printk(KERN_INFO "x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",
	       smp_processor_id(), boot_pat_state, pat);
}

#undef PAT

static char *cattr_name(unsigned long flags)
{
	switch (flags & _PAGE_CACHE_MASK) {
		case _PAGE_CACHE_UC:		return "uncached";
		case _PAGE_CACHE_UC_MINUS:	return "uncached-minus";
		case _PAGE_CACHE_WB:		return "write-back";
		case _PAGE_CACHE_WC:		return "write-combining";
		default:			return "broken";
	}
}

/*
 * The global memtype list keeps track of memory type for specific
 * physical memory areas. Conflicting memory types in different
 * mappings can cause CPU cache corruption. To avoid this we keep track.
 *
 * The list is sorted based on starting address and can contain multiple
 * entries for each address (this allows reference counting for overlapping
 * areas). All the aliases have the same cache attributes of course.
 * Zero attributes are represented as holes.
 *
 * Currently the data structure is a list because the number of mappings
 * are expected to be relatively small. If this should be a problem
 * it could be changed to a rbtree or similar.
 *
 * memtype_lock protects the whole list.
 */

struct memtype {
	u64 start;
	u64 end;
	unsigned long type;
	struct list_head nd;
};

static LIST_HEAD(memtype_list);
static DEFINE_SPINLOCK(memtype_lock); 	/* protects memtype list */

/*
 * Does intersection of PAT memory type and MTRR memory type and returns
 * the resulting memory type as PAT understands it.
 * (Type in pat and mtrr will not have same value)
 * The intersection is based on "Effective Memory Type" tables in IA-32
 * SDM vol 3a
 */
static int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
				unsigned long *ret_prot)
{
	unsigned long pat_type;
	u8 mtrr_type;

	mtrr_type = mtrr_type_lookup(start, end);
	if (mtrr_type == 0xFF) {		/* MTRR not enabled */
		*ret_prot = prot;
		return 0;
	}
	if (mtrr_type == 0xFE) {		/* MTRR match error */
		*ret_prot = _PAGE_CACHE_UC;
		return -1;
	}
	if (mtrr_type != MTRR_TYPE_UNCACHABLE &&
	    mtrr_type != MTRR_TYPE_WRBACK &&
	    mtrr_type != MTRR_TYPE_WRCOMB) {	/* MTRR type unhandled */
		*ret_prot = _PAGE_CACHE_UC;
		return -1;
	}

	pat_type = prot & _PAGE_CACHE_MASK;
	prot &= (~_PAGE_CACHE_MASK);

	/* Currently doing intersection by hand. Optimize it later. */
	if (pat_type == _PAGE_CACHE_WC) {
		*ret_prot = prot | _PAGE_CACHE_WC;
	} else if (pat_type == _PAGE_CACHE_UC_MINUS) {
		*ret_prot = prot | _PAGE_CACHE_UC_MINUS;
	} else if (pat_type == _PAGE_CACHE_UC ||
	           mtrr_type == MTRR_TYPE_UNCACHABLE) {
		*ret_prot = prot | _PAGE_CACHE_UC;
	} else if (mtrr_type == MTRR_TYPE_WRCOMB) {
		*ret_prot = prot | _PAGE_CACHE_WC;
	} else {
		*ret_prot = prot | _PAGE_CACHE_WB;
	}

	return 0;
}

/*
 * req_type typically has one of the:
 * - _PAGE_CACHE_WB
 * - _PAGE_CACHE_WC
 * - _PAGE_CACHE_UC_MINUS
 * - _PAGE_CACHE_UC
 *
 * req_type will have a special case value '-1', when requester want to inherit
 * the memory type from mtrr (if WB), existing PAT, defaulting to UC_MINUS.
 *
 * If ret_type is NULL, function will return an error if it cannot reserve the
 * region with req_type. If ret_type is non-null, function will return
 * available type in ret_type in case of no error. In case of any error
 * it will return a negative return value.
 */
int reserve_memtype(u64 start, u64 end, unsigned long req_type,
			unsigned long *ret_type)
{
	struct memtype *new_entry = NULL;
	struct memtype *parse;
	unsigned long actual_type;
	int err = 0;

	/* Only track when pat_wc_enabled */
	if (!pat_wc_enabled) {
		/* This is identical to page table setting without PAT */
		if (ret_type) {
			if (req_type == -1) {
				*ret_type = _PAGE_CACHE_WB;
			} else {
				*ret_type = req_type;
			}
		}
		return 0;
	}

	/* Low ISA region is always mapped WB in page table. No need to track */
	if (start >= ISA_START_ADDRESS && (end - 1) <= ISA_END_ADDRESS) {
		if (ret_type)
			*ret_type = _PAGE_CACHE_WB;

		return 0;
	}

	if (req_type == -1) {
		/*
		 * Special case where caller wants to inherit from mtrr or
		 * existing pat mapping, defaulting to UC_MINUS in case of
		 * no match.
		 */
		u8 mtrr_type = mtrr_type_lookup(start, end);
		if (mtrr_type == 0xFE) { /* MTRR match error */
			err = -1;
		}

		if (mtrr_type == MTRR_TYPE_WRBACK) {
			req_type = _PAGE_CACHE_WB;
			actual_type = _PAGE_CACHE_WB;
		} else {
			req_type = _PAGE_CACHE_UC_MINUS;
			actual_type = _PAGE_CACHE_UC_MINUS;
		}
	} else {
		req_type &= _PAGE_CACHE_MASK;
		err = pat_x_mtrr_type(start, end, req_type, &actual_type);
	}

	if (err) {
		if (ret_type)
			*ret_type = actual_type;

		return -EINVAL;
	}

	new_entry  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
	if (!new_entry)
		return -ENOMEM;

	new_entry->start = start;
	new_entry->end = end;
	new_entry->type = actual_type;

	if (ret_type)
		*ret_type = actual_type;

	spin_lock(&memtype_lock);

	/* Search for existing mapping that overlaps the current range */
	list_for_each_entry(parse, &memtype_list, nd) {
		struct memtype *saved_ptr;

		if (parse->start >= end) {
			pr_debug("New Entry\n");
			list_add(&new_entry->nd, parse->nd.prev);
			new_entry = NULL;
			break;
		}

		if (start <= parse->start && end >= parse->start) {
			if (actual_type != parse->type && ret_type) {
				actual_type = parse->type;
				*ret_type = actual_type;
				new_entry->type = actual_type;
			}

			if (actual_type != parse->type) {
				printk(
		KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
					current->comm, current->pid,
					start, end,
					cattr_name(actual_type),
					cattr_name(parse->type));
				err = -EBUSY;
				break;
			}

			saved_ptr = parse;
			/*
			 * Check to see whether the request overlaps more
			 * than one entry in the list
			 */
			list_for_each_entry_continue(parse, &memtype_list, nd) {
				if (end <= parse->start) {
					break;
				}

				if (actual_type != parse->type) {
					printk(
		KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
						current->comm, current->pid,
						start, end,
						cattr_name(actual_type),
						cattr_name(parse->type));
					err = -EBUSY;
					break;
				}
			}

			if (err) {
				break;
			}

			pr_debug("Overlap at 0x%Lx-0x%Lx\n",
			       saved_ptr->start, saved_ptr->end);
			/* No conflict. Go ahead and add this new entry */
			list_add(&new_entry->nd, saved_ptr->nd.prev);
			new_entry = NULL;
			break;
		}

		if (start < parse->end) {
			if (actual_type != parse->type && ret_type) {
				actual_type = parse->type;
				*ret_type = actual_type;
				new_entry->type = actual_type;
			}

			if (actual_type != parse->type) {
				printk(
		KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
					current->comm, current->pid,
					start, end,
					cattr_name(actual_type),
					cattr_name(parse->type));
				err = -EBUSY;
				break;
			}

			saved_ptr = parse;
			/*
			 * Check to see whether the request overlaps more
			 * than one entry in the list
			 */
			list_for_each_entry_continue(parse, &memtype_list, nd) {
				if (end <= parse->start) {
					break;
				}

				if (actual_type != parse->type) {
					printk(
		KERN_INFO "%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
						current->comm, current->pid,
						start, end,
						cattr_name(actual_type),
						cattr_name(parse->type));
					err = -EBUSY;
					break;
				}
			}

			if (err) {
				break;
			}

			printk(KERN_INFO "Overlap at 0x%Lx-0x%Lx\n",
			       saved_ptr->start, saved_ptr->end);
			/* No conflict. Go ahead and add this new entry */
			list_add(&new_entry->nd, &saved_ptr->nd);
			new_entry = NULL;
			break;
		}
	}

	if (err) {
		printk(KERN_INFO
	"reserve_memtype failed 0x%Lx-0x%Lx, track %s, req %s\n",
			start, end, cattr_name(new_entry->type),
			cattr_name(req_type));
		kfree(new_entry);
		spin_unlock(&memtype_lock);
		return err;
	}

	if (new_entry) {
		/* No conflict. Not yet added to the list. Add to the tail */
		list_add_tail(&new_entry->nd, &memtype_list);
		pr_debug("New Entry\n");
	}

	if (ret_type) {
		pr_debug(
	"reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
			start, end, cattr_name(actual_type),
			cattr_name(req_type), cattr_name(*ret_type));
	} else {
		pr_debug(
	"reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s\n",
			start, end, cattr_name(actual_type),
			cattr_name(req_type));
	}

	spin_unlock(&memtype_lock);
	return err;
}

int free_memtype(u64 start, u64 end)
{
	struct memtype *ml;
	int err = -EINVAL;

	/* Only track when pat_wc_enabled */
	if (!pat_wc_enabled) {
		return 0;
	}

	/* Low ISA region is always mapped WB. No need to track */
	if (start >= ISA_START_ADDRESS && end <= ISA_END_ADDRESS) {
		return 0;
	}

	spin_lock(&memtype_lock);
	list_for_each_entry(ml, &memtype_list, nd) {
		if (ml->start == start && ml->end == end) {
			list_del(&ml->nd);
			kfree(ml);
			err = 0;
			break;
		}
	}
	spin_unlock(&memtype_lock);

	if (err) {
		printk(KERN_INFO "%s:%d freeing invalid memtype %Lx-%Lx\n",
			current->comm, current->pid, start, end);
	}

	pr_debug("free_memtype request 0x%Lx-0x%Lx\n", start, end);
	return err;
}


/*
 * /dev/mem mmap interface. The memtype used for mapping varies:
 * - Use UC for mappings with O_SYNC flag
 * - Without O_SYNC flag, if there is any conflict in reserve_memtype,
 *   inherit the memtype from existing mapping.
 * - Else use UC_MINUS memtype (for backward compatibility with existing
 *   X drivers.
 */
pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
				unsigned long size, pgprot_t vma_prot)
{
	return vma_prot;
}

#ifdef CONFIG_NONPROMISC_DEVMEM
/* This check is done in drivers/char/mem.c in case of NONPROMISC_DEVMEM*/
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
	return 1;
}
#else
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
	u64 from = ((u64)pfn) << PAGE_SHIFT;
	u64 to = from + size;
	u64 cursor = from;

	while (cursor < to) {
		if (!devmem_is_allowed(pfn)) {
			printk(KERN_INFO
		"Program %s tried to access /dev/mem between %Lx->%Lx.\n",
				current->comm, from, to);
			return 0;
		}
		cursor += PAGE_SIZE;
		pfn++;
	}
	return 1;
}
#endif /* CONFIG_NONPROMISC_DEVMEM */

int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
				unsigned long size, pgprot_t *vma_prot)
{
	u64 offset = ((u64) pfn) << PAGE_SHIFT;
	unsigned long flags = _PAGE_CACHE_UC_MINUS;
	unsigned long ret_flags;
	int retval;

	if (!range_is_allowed(pfn, size))
		return 0;

	if (file->f_flags & O_SYNC) {
		flags = _PAGE_CACHE_UC;
	}

#ifdef CONFIG_X86_32
	/*
	 * On the PPro and successors, the MTRRs are used to set
	 * memory types for physical addresses outside main memory,
	 * so blindly setting UC or PWT on those pages is wrong.
	 * For Pentiums and earlier, the surround logic should disable
	 * caching for the high addresses through the KEN pin, but
	 * we maintain the tradition of paranoia in this code.
	 */
	if (!pat_wc_enabled &&
	    ! ( test_bit(X86_FEATURE_MTRR, boot_cpu_data.x86_capability) ||
		test_bit(X86_FEATURE_K6_MTRR, boot_cpu_data.x86_capability) ||
		test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) ||
		test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability)) &&
	   (pfn << PAGE_SHIFT) >= __pa(high_memory)) {
		flags = _PAGE_CACHE_UC;
	}
#endif

	/*
	 * With O_SYNC, we can only take UC mapping. Fail if we cannot.
	 * Without O_SYNC, we want to get
	 * - WB for WB-able memory and no other conflicting mappings
	 * - UC_MINUS for non-WB-able memory with no other conflicting mappings
	 * - Inherit from confliting mappings otherwise
	 */
	if (flags != _PAGE_CACHE_UC_MINUS) {
		retval = reserve_memtype(offset, offset + size, flags, NULL);
	} else {
		retval = reserve_memtype(offset, offset + size, -1, &ret_flags);
	}

	if (retval < 0)
		return 0;

	flags = ret_flags;

	if (pfn <= max_pfn_mapped &&
            ioremap_change_attr((unsigned long)__va(offset), size, flags) < 0) {
		free_memtype(offset, offset + size);
		printk(KERN_INFO
		"%s:%d /dev/mem ioremap_change_attr failed %s for %Lx-%Lx\n",
			current->comm, current->pid,
			cattr_name(flags),
			offset, offset + size);
		return 0;
	}

	*vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) |
			     flags);
	return 1;
}

void map_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
{
	u64 addr = (u64)pfn << PAGE_SHIFT;
	unsigned long flags;
	unsigned long want_flags = (pgprot_val(vma_prot) & _PAGE_CACHE_MASK);

	reserve_memtype(addr, addr + size, want_flags, &flags);
	if (flags != want_flags) {
		printk(KERN_INFO
		"%s:%d /dev/mem expected mapping type %s for %Lx-%Lx, got %s\n",
			current->comm, current->pid,
			cattr_name(want_flags),
			addr, addr + size,
			cattr_name(flags));
	}
}

void unmap_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
{
	u64 addr = (u64)pfn << PAGE_SHIFT;

	free_memtype(addr, addr + size);
}