2 * Handle caching attributes in page tables (PAT)
4 * Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
5 * Suresh B Siddha <suresh.b.siddha@intel.com>
7 * Loosely based on earlier PAT patchset from Eric Biederman and Andi Kleen.
11 #include <linux/kernel.h>
12 #include <linux/gfp.h>
14 #include <linux/bootmem.h>
17 #include <asm/tlbflush.h>
18 #include <asm/processor.h>
20 #include <asm/pgtable.h>
23 #include <asm/cacheflush.h>
24 #include <asm/fcntl.h>
29 int __read_mostly pat_enabled
= 1;
31 void __cpuinit
pat_disable(char *reason
)
34 printk(KERN_INFO
"%s\n", reason
);
37 static int __init
nopat(char *str
)
39 pat_disable("PAT support disabled.");
42 early_param("nopat", nopat
);
46 static int debug_enable
;
47 static int __init
pat_debug_setup(char *str
)
52 __setup("debugpat", pat_debug_setup
);
54 #define dprintk(fmt, arg...) \
55 do { if (debug_enable) printk(KERN_INFO fmt, ##arg); } while (0)
58 static u64 __read_mostly boot_pat_state
;
61 PAT_UC
= 0, /* uncached */
62 PAT_WC
= 1, /* Write combining */
63 PAT_WT
= 4, /* Write Through */
64 PAT_WP
= 5, /* Write Protected */
65 PAT_WB
= 6, /* Write Back (default) */
66 PAT_UC_MINUS
= 7, /* UC, but can be overriden by MTRR */
69 #define PAT(x, y) ((u64)PAT_ ## y << ((x)*8))
79 if (!cpu_has_pat
&& boot_pat_state
) {
81 * If this happens we are on a secondary CPU, but
82 * switched to PAT on the boot CPU. We have no way to
85 printk(KERN_ERR
"PAT enabled, "
86 "but not supported by secondary CPU\n");
90 /* Set PWT to Write-Combining. All other bits stay the same */
92 * PTE encoding used in Linux:
97 * 000 WB _PAGE_CACHE_WB
98 * 001 WC _PAGE_CACHE_WC
99 * 010 UC- _PAGE_CACHE_UC_MINUS
100 * 011 UC _PAGE_CACHE_UC
103 pat
= PAT(0, WB
) | PAT(1, WC
) | PAT(2, UC_MINUS
) | PAT(3, UC
) |
104 PAT(4, WB
) | PAT(5, WC
) | PAT(6, UC_MINUS
) | PAT(7, UC
);
108 rdmsrl(MSR_IA32_CR_PAT
, boot_pat_state
);
110 wrmsrl(MSR_IA32_CR_PAT
, pat
);
111 printk(KERN_INFO
"x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",
112 smp_processor_id(), boot_pat_state
, pat
);
117 static char *cattr_name(unsigned long flags
)
119 switch (flags
& _PAGE_CACHE_MASK
) {
120 case _PAGE_CACHE_UC
: return "uncached";
121 case _PAGE_CACHE_UC_MINUS
: return "uncached-minus";
122 case _PAGE_CACHE_WB
: return "write-back";
123 case _PAGE_CACHE_WC
: return "write-combining";
124 default: return "broken";
129 * The global memtype list keeps track of memory type for specific
130 * physical memory areas. Conflicting memory types in different
131 * mappings can cause CPU cache corruption. To avoid this we keep track.
133 * The list is sorted based on starting address and can contain multiple
134 * entries for each address (this allows reference counting for overlapping
135 * areas). All the aliases have the same cache attributes of course.
136 * Zero attributes are represented as holes.
138 * Currently the data structure is a list because the number of mappings
139 * are expected to be relatively small. If this should be a problem
140 * it could be changed to a rbtree or similar.
142 * memtype_lock protects the whole list.
152 static LIST_HEAD(memtype_list
);
153 static DEFINE_SPINLOCK(memtype_lock
); /* protects memtype list */
156 * Does intersection of PAT memory type and MTRR memory type and returns
157 * the resulting memory type as PAT understands it.
158 * (Type in pat and mtrr will not have same value)
159 * The intersection is based on "Effective Memory Type" tables in IA-32
162 static unsigned long pat_x_mtrr_type(u64 start
, u64 end
, unsigned long req_type
)
167 * We return the PAT request directly for types where PAT takes
168 * precedence with respect to MTRR and for UC_MINUS.
169 * Consistency checks with other PAT requests is done later
170 * while going through memtype list.
172 if (req_type
== _PAGE_CACHE_WC
||
173 req_type
== _PAGE_CACHE_UC_MINUS
||
174 req_type
== _PAGE_CACHE_UC
)
178 * Look for MTRR hint to get the effective type in case where PAT
181 mtrr_type
= mtrr_type_lookup(start
, end
);
182 if (mtrr_type
== MTRR_TYPE_UNCACHABLE
)
183 return _PAGE_CACHE_UC
;
184 if (mtrr_type
== MTRR_TYPE_WRCOMB
)
185 return _PAGE_CACHE_WC
;
186 return _PAGE_CACHE_WB
;
190 * req_type typically has one of the:
193 * - _PAGE_CACHE_UC_MINUS
196 * req_type will have a special case value '-1', when requester want to inherit
197 * the memory type from mtrr (if WB), existing PAT, defaulting to UC_MINUS.
199 * If ret_type is NULL, function will return an error if it cannot reserve the
200 * region with req_type. If ret_type is non-null, function will return
201 * available type in ret_type in case of no error. In case of any error
202 * it will return a negative return value.
204 int reserve_memtype(u64 start
, u64 end
, unsigned long req_type
,
205 unsigned long *ret_type
)
207 struct memtype
*new_entry
= NULL
;
208 struct memtype
*parse
;
209 unsigned long actual_type
;
212 /* Only track when pat_enabled */
214 /* This is identical to page table setting without PAT */
216 if (req_type
== -1) {
217 *ret_type
= _PAGE_CACHE_WB
;
219 *ret_type
= req_type
& _PAGE_CACHE_MASK
;
225 /* Low ISA region is always mapped WB in page table. No need to track */
226 if (start
>= ISA_START_ADDRESS
&& (end
- 1) <= ISA_END_ADDRESS
) {
228 *ret_type
= _PAGE_CACHE_WB
;
233 if (req_type
== -1) {
235 * Call mtrr_lookup to get the type hint. This is an
236 * optimization for /dev/mem mmap'ers into WB memory (BIOS
237 * tools and ACPI tools). Use WB request for WB memory and use
238 * UC_MINUS otherwise.
240 u8 mtrr_type
= mtrr_type_lookup(start
, end
);
242 if (mtrr_type
== MTRR_TYPE_WRBACK
) {
243 req_type
= _PAGE_CACHE_WB
;
244 actual_type
= _PAGE_CACHE_WB
;
246 req_type
= _PAGE_CACHE_UC_MINUS
;
247 actual_type
= _PAGE_CACHE_UC_MINUS
;
250 req_type
&= _PAGE_CACHE_MASK
;
251 actual_type
= pat_x_mtrr_type(start
, end
, req_type
);
254 new_entry
= kmalloc(sizeof(struct memtype
), GFP_KERNEL
);
258 new_entry
->start
= start
;
259 new_entry
->end
= end
;
260 new_entry
->type
= actual_type
;
263 *ret_type
= actual_type
;
265 spin_lock(&memtype_lock
);
267 /* Search for existing mapping that overlaps the current range */
268 list_for_each_entry(parse
, &memtype_list
, nd
) {
269 struct memtype
*saved_ptr
;
271 if (parse
->start
>= end
) {
272 dprintk("New Entry\n");
273 list_add(&new_entry
->nd
, parse
->nd
.prev
);
278 if (start
<= parse
->start
&& end
>= parse
->start
) {
279 if (actual_type
!= parse
->type
&& ret_type
) {
280 actual_type
= parse
->type
;
281 *ret_type
= actual_type
;
282 new_entry
->type
= actual_type
;
285 if (actual_type
!= parse
->type
) {
287 KERN_INFO
"%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
288 current
->comm
, current
->pid
,
290 cattr_name(actual_type
),
291 cattr_name(parse
->type
));
298 * Check to see whether the request overlaps more
299 * than one entry in the list
301 list_for_each_entry_continue(parse
, &memtype_list
, nd
) {
302 if (end
<= parse
->start
) {
306 if (actual_type
!= parse
->type
) {
308 KERN_INFO
"%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
309 current
->comm
, current
->pid
,
311 cattr_name(actual_type
),
312 cattr_name(parse
->type
));
322 dprintk("Overlap at 0x%Lx-0x%Lx\n",
323 saved_ptr
->start
, saved_ptr
->end
);
324 /* No conflict. Go ahead and add this new entry */
325 list_add(&new_entry
->nd
, saved_ptr
->nd
.prev
);
330 if (start
< parse
->end
) {
331 if (actual_type
!= parse
->type
&& ret_type
) {
332 actual_type
= parse
->type
;
333 *ret_type
= actual_type
;
334 new_entry
->type
= actual_type
;
337 if (actual_type
!= parse
->type
) {
339 KERN_INFO
"%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
340 current
->comm
, current
->pid
,
342 cattr_name(actual_type
),
343 cattr_name(parse
->type
));
350 * Check to see whether the request overlaps more
351 * than one entry in the list
353 list_for_each_entry_continue(parse
, &memtype_list
, nd
) {
354 if (end
<= parse
->start
) {
358 if (actual_type
!= parse
->type
) {
360 KERN_INFO
"%s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
361 current
->comm
, current
->pid
,
363 cattr_name(actual_type
),
364 cattr_name(parse
->type
));
374 dprintk("Overlap at 0x%Lx-0x%Lx\n",
375 saved_ptr
->start
, saved_ptr
->end
);
376 /* No conflict. Go ahead and add this new entry */
377 list_add(&new_entry
->nd
, &saved_ptr
->nd
);
385 "reserve_memtype failed 0x%Lx-0x%Lx, track %s, req %s\n",
386 start
, end
, cattr_name(new_entry
->type
),
387 cattr_name(req_type
));
389 spin_unlock(&memtype_lock
);
394 /* No conflict. Not yet added to the list. Add to the tail */
395 list_add_tail(&new_entry
->nd
, &memtype_list
);
396 dprintk("New Entry\n");
401 "reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
402 start
, end
, cattr_name(actual_type
),
403 cattr_name(req_type
), cattr_name(*ret_type
));
406 "reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s\n",
407 start
, end
, cattr_name(actual_type
),
408 cattr_name(req_type
));
411 spin_unlock(&memtype_lock
);
415 int free_memtype(u64 start
, u64 end
)
420 /* Only track when pat_enabled */
425 /* Low ISA region is always mapped WB. No need to track */
426 if (start
>= ISA_START_ADDRESS
&& end
<= ISA_END_ADDRESS
) {
430 spin_lock(&memtype_lock
);
431 list_for_each_entry(ml
, &memtype_list
, nd
) {
432 if (ml
->start
== start
&& ml
->end
== end
) {
439 spin_unlock(&memtype_lock
);
442 printk(KERN_INFO
"%s:%d freeing invalid memtype %Lx-%Lx\n",
443 current
->comm
, current
->pid
, start
, end
);
446 dprintk("free_memtype request 0x%Lx-0x%Lx\n", start
, end
);
452 * /dev/mem mmap interface. The memtype used for mapping varies:
453 * - Use UC for mappings with O_SYNC flag
454 * - Without O_SYNC flag, if there is any conflict in reserve_memtype,
455 * inherit the memtype from existing mapping.
456 * - Else use UC_MINUS memtype (for backward compatibility with existing
459 pgprot_t
phys_mem_access_prot(struct file
*file
, unsigned long pfn
,
460 unsigned long size
, pgprot_t vma_prot
)
465 #ifdef CONFIG_NONPROMISC_DEVMEM
466 /* This check is done in drivers/char/mem.c in case of NONPROMISC_DEVMEM*/
467 static inline int range_is_allowed(unsigned long pfn
, unsigned long size
)
472 static inline int range_is_allowed(unsigned long pfn
, unsigned long size
)
474 u64 from
= ((u64
)pfn
) << PAGE_SHIFT
;
475 u64 to
= from
+ size
;
478 while (cursor
< to
) {
479 if (!devmem_is_allowed(pfn
)) {
481 "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
482 current
->comm
, from
, to
);
490 #endif /* CONFIG_NONPROMISC_DEVMEM */
492 int phys_mem_access_prot_allowed(struct file
*file
, unsigned long pfn
,
493 unsigned long size
, pgprot_t
*vma_prot
)
495 u64 offset
= ((u64
) pfn
) << PAGE_SHIFT
;
496 unsigned long flags
= _PAGE_CACHE_UC_MINUS
;
499 if (!range_is_allowed(pfn
, size
))
502 if (file
->f_flags
& O_SYNC
) {
503 flags
= _PAGE_CACHE_UC
;
508 * On the PPro and successors, the MTRRs are used to set
509 * memory types for physical addresses outside main memory,
510 * so blindly setting UC or PWT on those pages is wrong.
511 * For Pentiums and earlier, the surround logic should disable
512 * caching for the high addresses through the KEN pin, but
513 * we maintain the tradition of paranoia in this code.
516 !(boot_cpu_has(X86_FEATURE_MTRR
) ||
517 boot_cpu_has(X86_FEATURE_K6_MTRR
) ||
518 boot_cpu_has(X86_FEATURE_CYRIX_ARR
) ||
519 boot_cpu_has(X86_FEATURE_CENTAUR_MCR
)) &&
520 (pfn
<< PAGE_SHIFT
) >= __pa(high_memory
)) {
521 flags
= _PAGE_CACHE_UC
;
526 * With O_SYNC, we can only take UC mapping. Fail if we cannot.
527 * Without O_SYNC, we want to get
528 * - WB for WB-able memory and no other conflicting mappings
529 * - UC_MINUS for non-WB-able memory with no other conflicting mappings
530 * - Inherit from confliting mappings otherwise
532 if (flags
!= _PAGE_CACHE_UC_MINUS
) {
533 retval
= reserve_memtype(offset
, offset
+ size
, flags
, NULL
);
535 retval
= reserve_memtype(offset
, offset
+ size
, -1, &flags
);
541 if (pfn
<= max_pfn_mapped
&&
542 ioremap_change_attr((unsigned long)__va(offset
), size
, flags
) < 0) {
543 free_memtype(offset
, offset
+ size
);
545 "%s:%d /dev/mem ioremap_change_attr failed %s for %Lx-%Lx\n",
546 current
->comm
, current
->pid
,
548 offset
, (unsigned long long)(offset
+ size
));
552 *vma_prot
= __pgprot((pgprot_val(*vma_prot
) & ~_PAGE_CACHE_MASK
) |
557 void map_devmem(unsigned long pfn
, unsigned long size
, pgprot_t vma_prot
)
559 u64 addr
= (u64
)pfn
<< PAGE_SHIFT
;
561 unsigned long want_flags
= (pgprot_val(vma_prot
) & _PAGE_CACHE_MASK
);
563 reserve_memtype(addr
, addr
+ size
, want_flags
, &flags
);
564 if (flags
!= want_flags
) {
566 "%s:%d /dev/mem expected mapping type %s for %Lx-%Lx, got %s\n",
567 current
->comm
, current
->pid
,
568 cattr_name(want_flags
),
569 addr
, (unsigned long long)(addr
+ size
),
574 void unmap_devmem(unsigned long pfn
, unsigned long size
, pgprot_t vma_prot
)
576 u64 addr
= (u64
)pfn
<< PAGE_SHIFT
;
578 free_memtype(addr
, addr
+ size
);