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.
10 #include <linux/seq_file.h>
11 #include <linux/bootmem.h>
12 #include <linux/debugfs.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/gfp.h>
18 #include <linux/rbtree.h>
20 #include <asm/cacheflush.h>
21 #include <asm/processor.h>
22 #include <asm/tlbflush.h>
23 #include <asm/pgtable.h>
24 #include <asm/fcntl.h>
33 int __read_mostly pat_enabled = 1;
35 static inline void pat_disable(const char *reason)
38 printk(KERN_INFO "%s\n", reason);
41 static int __init nopat(char *str)
43 pat_disable("PAT support disabled.");
46 early_param("nopat", nopat);
48 static inline void pat_disable(const char *reason)
55 static int debug_enable;
57 static int __init pat_debug_setup(char *str)
62 __setup("debugpat", pat_debug_setup);
64 #define dprintk(fmt, arg...) \
65 do { if (debug_enable) printk(KERN_INFO fmt, ##arg); } while (0)
68 static u64 __read_mostly boot_pat_state;
71 PAT_UC = 0, /* uncached */
72 PAT_WC = 1, /* Write combining */
73 PAT_WT = 4, /* Write Through */
74 PAT_WP = 5, /* Write Protected */
75 PAT_WB = 6, /* Write Back (default) */
76 PAT_UC_MINUS = 7, /* UC, but can be overriden by MTRR */
79 #define PAT(x, y) ((u64)PAT_ ## y << ((x)*8))
84 bool boot_cpu = !boot_pat_state;
90 if (!boot_pat_state) {
91 pat_disable("PAT not supported by CPU.");
95 * If this happens we are on a secondary CPU, but
96 * switched to PAT on the boot CPU. We have no way to
99 printk(KERN_ERR "PAT enabled, "
100 "but not supported by secondary CPU\n");
105 /* Set PWT to Write-Combining. All other bits stay the same */
107 * PTE encoding used in Linux:
112 * 000 WB _PAGE_CACHE_WB
113 * 001 WC _PAGE_CACHE_WC
114 * 010 UC- _PAGE_CACHE_UC_MINUS
115 * 011 UC _PAGE_CACHE_UC
118 pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
119 PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
123 rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
125 wrmsrl(MSR_IA32_CR_PAT, pat);
128 printk(KERN_INFO "x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",
129 smp_processor_id(), boot_pat_state, pat);
134 static char *cattr_name(unsigned long flags)
136 switch (flags & _PAGE_CACHE_MASK) {
137 case _PAGE_CACHE_UC: return "uncached";
138 case _PAGE_CACHE_UC_MINUS: return "uncached-minus";
139 case _PAGE_CACHE_WB: return "write-back";
140 case _PAGE_CACHE_WC: return "write-combining";
141 default: return "broken";
146 * The global memtype list keeps track of memory type for specific
147 * physical memory areas. Conflicting memory types in different
148 * mappings can cause CPU cache corruption. To avoid this we keep track.
150 * The list is sorted based on starting address and can contain multiple
151 * entries for each address (this allows reference counting for overlapping
152 * areas). All the aliases have the same cache attributes of course.
153 * Zero attributes are represented as holes.
155 * The data structure is a list that is also organized as an rbtree
156 * sorted on the start address of memtype range.
158 * memtype_lock protects both the linear list and rbtree.
169 static struct rb_root memtype_rbroot = RB_ROOT;
170 static LIST_HEAD(memtype_list);
171 static DEFINE_SPINLOCK(memtype_lock); /* protects memtype list */
173 static struct memtype *memtype_rb_search(struct rb_root *root, u64 start)
175 struct rb_node *node = root->rb_node;
176 struct memtype *last_lower = NULL;
179 struct memtype *data = container_of(node, struct memtype, rb);
181 if (data->start < start) {
183 node = node->rb_right;
184 } else if (data->start > start) {
185 node = node->rb_left;
190 /* Will return NULL if there is no entry with its start <= start */
194 static void memtype_rb_insert(struct rb_root *root, struct memtype *data)
196 struct rb_node **new = &(root->rb_node);
197 struct rb_node *parent = NULL;
200 struct memtype *this = container_of(*new, struct memtype, rb);
203 if (data->start <= this->start)
204 new = &((*new)->rb_left);
205 else if (data->start > this->start)
206 new = &((*new)->rb_right);
209 rb_link_node(&data->rb, parent, new);
210 rb_insert_color(&data->rb, root);
214 * Does intersection of PAT memory type and MTRR memory type and returns
215 * the resulting memory type as PAT understands it.
216 * (Type in pat and mtrr will not have same value)
217 * The intersection is based on "Effective Memory Type" tables in IA-32
220 static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
223 * Look for MTRR hint to get the effective type in case where PAT
226 if (req_type == _PAGE_CACHE_WB) {
229 mtrr_type = mtrr_type_lookup(start, end);
230 if (mtrr_type != MTRR_TYPE_WRBACK)
231 return _PAGE_CACHE_UC_MINUS;
233 return _PAGE_CACHE_WB;
240 chk_conflict(struct memtype *new, struct memtype *entry, unsigned long *type)
242 if (new->type != entry->type) {
244 new->type = entry->type;
250 /* check overlaps with more than one entry in the list */
251 list_for_each_entry_continue(entry, &memtype_list, nd) {
252 if (new->end <= entry->start)
254 else if (new->type != entry->type)
260 printk(KERN_INFO "%s:%d conflicting memory types "
261 "%Lx-%Lx %s<->%s\n", current->comm, current->pid, new->start,
262 new->end, cattr_name(new->type), cattr_name(entry->type));
266 static int pat_pagerange_is_ram(unsigned long start, unsigned long end)
268 int ram_page = 0, not_rampage = 0;
269 unsigned long page_nr;
271 for (page_nr = (start >> PAGE_SHIFT); page_nr < (end >> PAGE_SHIFT);
274 * For legacy reasons, physical address range in the legacy ISA
275 * region is tracked as non-RAM. This will allow users of
276 * /dev/mem to map portions of legacy ISA region, even when
277 * some of those portions are listed(or not even listed) with
278 * different e820 types(RAM/reserved/..)
280 if (page_nr >= (ISA_END_ADDRESS >> PAGE_SHIFT) &&
281 page_is_ram(page_nr))
286 if (ram_page == not_rampage)
294 * For RAM pages, we use page flags to mark the pages with appropriate type.
295 * Here we do two pass:
296 * - Find the memtype of all the pages in the range, look for any conflicts
297 * - In case of no conflicts, set the new memtype for pages in the range
299 * Caller must hold memtype_lock for atomicity.
301 static int reserve_ram_pages_type(u64 start, u64 end, unsigned long req_type,
302 unsigned long *new_type)
307 if (req_type == _PAGE_CACHE_UC) {
308 /* We do not support strong UC */
310 req_type = _PAGE_CACHE_UC_MINUS;
313 for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
316 page = pfn_to_page(pfn);
317 type = get_page_memtype(page);
319 printk(KERN_INFO "reserve_ram_pages_type failed "
320 "0x%Lx-0x%Lx, track 0x%lx, req 0x%lx\n",
321 start, end, type, req_type);
330 *new_type = req_type;
332 for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
333 page = pfn_to_page(pfn);
334 set_page_memtype(page, req_type);
339 static int free_ram_pages_type(u64 start, u64 end)
344 for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
345 page = pfn_to_page(pfn);
346 set_page_memtype(page, -1);
352 * req_type typically has one of the:
355 * - _PAGE_CACHE_UC_MINUS
358 * req_type will have a special case value '-1', when requester want to inherit
359 * the memory type from mtrr (if WB), existing PAT, defaulting to UC_MINUS.
361 * If new_type is NULL, function will return an error if it cannot reserve the
362 * region with req_type. If new_type is non-NULL, function will return
363 * available type in new_type in case of no error. In case of any error
364 * it will return a negative return value.
366 int reserve_memtype(u64 start, u64 end, unsigned long req_type,
367 unsigned long *new_type)
369 struct memtype *new, *entry;
370 unsigned long actual_type;
371 struct list_head *where;
375 BUG_ON(start >= end); /* end is exclusive */
378 /* This is identical to page table setting without PAT */
381 *new_type = _PAGE_CACHE_WB;
382 else if (req_type == _PAGE_CACHE_WC)
383 *new_type = _PAGE_CACHE_UC_MINUS;
385 *new_type = req_type & _PAGE_CACHE_MASK;
390 /* Low ISA region is always mapped WB in page table. No need to track */
391 if (is_ISA_range(start, end - 1)) {
393 *new_type = _PAGE_CACHE_WB;
398 * Call mtrr_lookup to get the type hint. This is an
399 * optimization for /dev/mem mmap'ers into WB memory (BIOS
400 * tools and ACPI tools). Use WB request for WB memory and use
401 * UC_MINUS otherwise.
403 actual_type = pat_x_mtrr_type(start, end, req_type & _PAGE_CACHE_MASK);
406 *new_type = actual_type;
408 is_range_ram = pat_pagerange_is_ram(start, end);
409 if (is_range_ram == 1) {
411 spin_lock(&memtype_lock);
412 err = reserve_ram_pages_type(start, end, req_type, new_type);
413 spin_unlock(&memtype_lock);
416 } else if (is_range_ram < 0) {
420 new = kmalloc(sizeof(struct memtype), GFP_KERNEL);
426 new->type = actual_type;
428 spin_lock(&memtype_lock);
430 /* Search for existing mapping that overlaps the current range */
432 list_for_each_entry(entry, &memtype_list, nd) {
433 if (end <= entry->start) {
434 where = entry->nd.prev;
436 } else if (start <= entry->start) { /* end > entry->start */
437 err = chk_conflict(new, entry, new_type);
439 dprintk("Overlap at 0x%Lx-0x%Lx\n",
440 entry->start, entry->end);
441 where = entry->nd.prev;
444 } else if (start < entry->end) { /* start > entry->start */
445 err = chk_conflict(new, entry, new_type);
447 dprintk("Overlap at 0x%Lx-0x%Lx\n",
448 entry->start, entry->end);
451 * Move to right position in the linked
452 * list to add this new entry
454 list_for_each_entry_continue(entry,
456 if (start <= entry->start) {
457 where = entry->nd.prev;
467 printk(KERN_INFO "reserve_memtype failed 0x%Lx-0x%Lx, "
468 "track %s, req %s\n",
469 start, end, cattr_name(new->type), cattr_name(req_type));
471 spin_unlock(&memtype_lock);
477 list_add(&new->nd, where);
479 list_add_tail(&new->nd, &memtype_list);
481 memtype_rb_insert(&memtype_rbroot, new);
483 spin_unlock(&memtype_lock);
485 dprintk("reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
486 start, end, cattr_name(new->type), cattr_name(req_type),
487 new_type ? cattr_name(*new_type) : "-");
492 int free_memtype(u64 start, u64 end)
494 struct memtype *entry, *saved_entry;
501 /* Low ISA region is always mapped WB. No need to track */
502 if (is_ISA_range(start, end - 1))
505 is_range_ram = pat_pagerange_is_ram(start, end);
506 if (is_range_ram == 1) {
508 spin_lock(&memtype_lock);
509 err = free_ram_pages_type(start, end);
510 spin_unlock(&memtype_lock);
513 } else if (is_range_ram < 0) {
517 spin_lock(&memtype_lock);
519 entry = memtype_rb_search(&memtype_rbroot, start);
520 if (unlikely(entry == NULL))
524 * Saved entry points to an entry with start same or less than what
525 * we searched for. Now go through the list in both directions to look
526 * for the entry that matches with both start and end, with list stored
527 * in sorted start address
530 list_for_each_entry_from(entry, &memtype_list, nd) {
531 if (entry->start == start && entry->end == end) {
532 rb_erase(&entry->rb, &memtype_rbroot);
533 list_del(&entry->nd);
537 } else if (entry->start > start) {
546 list_for_each_entry_reverse(entry, &memtype_list, nd) {
547 if (entry->start == start && entry->end == end) {
548 rb_erase(&entry->rb, &memtype_rbroot);
549 list_del(&entry->nd);
553 } else if (entry->start < start) {
558 spin_unlock(&memtype_lock);
561 printk(KERN_INFO "%s:%d freeing invalid memtype %Lx-%Lx\n",
562 current->comm, current->pid, start, end);
565 dprintk("free_memtype request 0x%Lx-0x%Lx\n", start, end);
572 * lookup_memtype - Looksup the memory type for a physical address
573 * @paddr: physical address of which memory type needs to be looked up
575 * Only to be called when PAT is enabled
577 * Returns _PAGE_CACHE_WB, _PAGE_CACHE_WC, _PAGE_CACHE_UC_MINUS or
580 static unsigned long lookup_memtype(u64 paddr)
582 int rettype = _PAGE_CACHE_WB;
583 struct memtype *entry;
585 if (is_ISA_range(paddr, paddr + PAGE_SIZE - 1))
588 if (pat_pagerange_is_ram(paddr, paddr + PAGE_SIZE)) {
590 spin_lock(&memtype_lock);
591 page = pfn_to_page(paddr >> PAGE_SHIFT);
592 rettype = get_page_memtype(page);
593 spin_unlock(&memtype_lock);
595 * -1 from get_page_memtype() implies RAM page is in its
596 * default state and not reserved, and hence of type WB
599 rettype = _PAGE_CACHE_WB;
604 spin_lock(&memtype_lock);
606 entry = memtype_rb_search(&memtype_rbroot, paddr);
608 rettype = entry->type;
610 rettype = _PAGE_CACHE_UC_MINUS;
612 spin_unlock(&memtype_lock);
617 * io_reserve_memtype - Request a memory type mapping for a region of memory
618 * @start: start (physical address) of the region
619 * @end: end (physical address) of the region
620 * @type: A pointer to memtype, with requested type. On success, requested
621 * or any other compatible type that was available for the region is returned
623 * On success, returns 0
624 * On failure, returns non-zero
626 int io_reserve_memtype(resource_size_t start, resource_size_t end,
629 resource_size_t size = end - start;
630 unsigned long req_type = *type;
631 unsigned long new_type;
634 WARN_ON_ONCE(iomem_map_sanity_check(start, size));
636 ret = reserve_memtype(start, end, req_type, &new_type);
640 if (!is_new_memtype_allowed(start, size, req_type, new_type))
643 if (kernel_map_sync_memtype(start, size, new_type) < 0)
650 free_memtype(start, end);
657 * io_free_memtype - Release a memory type mapping for a region of memory
658 * @start: start (physical address) of the region
659 * @end: end (physical address) of the region
661 void io_free_memtype(resource_size_t start, resource_size_t end)
663 free_memtype(start, end);
666 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
667 unsigned long size, pgprot_t vma_prot)
672 #ifdef CONFIG_STRICT_DEVMEM
673 /* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM*/
674 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
679 /* This check is needed to avoid cache aliasing when PAT is enabled */
680 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
682 u64 from = ((u64)pfn) << PAGE_SHIFT;
683 u64 to = from + size;
689 while (cursor < to) {
690 if (!devmem_is_allowed(pfn)) {
692 "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
693 current->comm, from, to);
701 #endif /* CONFIG_STRICT_DEVMEM */
703 int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
704 unsigned long size, pgprot_t *vma_prot)
706 unsigned long flags = _PAGE_CACHE_WB;
708 if (!range_is_allowed(pfn, size))
711 if (file->f_flags & O_SYNC) {
712 flags = _PAGE_CACHE_UC_MINUS;
717 * On the PPro and successors, the MTRRs are used to set
718 * memory types for physical addresses outside main memory,
719 * so blindly setting UC or PWT on those pages is wrong.
720 * For Pentiums and earlier, the surround logic should disable
721 * caching for the high addresses through the KEN pin, but
722 * we maintain the tradition of paranoia in this code.
725 !(boot_cpu_has(X86_FEATURE_MTRR) ||
726 boot_cpu_has(X86_FEATURE_K6_MTRR) ||
727 boot_cpu_has(X86_FEATURE_CYRIX_ARR) ||
728 boot_cpu_has(X86_FEATURE_CENTAUR_MCR)) &&
729 (pfn << PAGE_SHIFT) >= __pa(high_memory)) {
730 flags = _PAGE_CACHE_UC;
734 *vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) |
740 * Change the memory type for the physial address range in kernel identity
741 * mapping space if that range is a part of identity map.
743 int kernel_map_sync_memtype(u64 base, unsigned long size, unsigned long flags)
747 if (base >= __pa(high_memory))
750 id_sz = (__pa(high_memory) < base + size) ?
751 __pa(high_memory) - base :
754 if (ioremap_change_attr((unsigned long)__va(base), id_sz, flags) < 0) {
756 "%s:%d ioremap_change_attr failed %s "
758 current->comm, current->pid,
760 base, (unsigned long long)(base + size));
767 * Internal interface to reserve a range of physical memory with prot.
768 * Reserved non RAM regions only and after successful reserve_memtype,
769 * this func also keeps identity mapping (if any) in sync with this new prot.
771 static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
776 unsigned long want_flags = (pgprot_val(*vma_prot) & _PAGE_CACHE_MASK);
777 unsigned long flags = want_flags;
779 is_ram = pat_pagerange_is_ram(paddr, paddr + size);
782 * reserve_pfn_range() for RAM pages. We do not refcount to keep
783 * track of number of mappings of RAM pages. We can assert that
784 * the type requested matches the type of first page in the range.
790 flags = lookup_memtype(paddr);
791 if (want_flags != flags) {
793 "%s:%d map pfn RAM range req %s for %Lx-%Lx, got %s\n",
794 current->comm, current->pid,
795 cattr_name(want_flags),
796 (unsigned long long)paddr,
797 (unsigned long long)(paddr + size),
799 *vma_prot = __pgprot((pgprot_val(*vma_prot) &
800 (~_PAGE_CACHE_MASK)) |
806 ret = reserve_memtype(paddr, paddr + size, want_flags, &flags);
810 if (flags != want_flags) {
812 !is_new_memtype_allowed(paddr, size, want_flags, flags)) {
813 free_memtype(paddr, paddr + size);
814 printk(KERN_ERR "%s:%d map pfn expected mapping type %s"
815 " for %Lx-%Lx, got %s\n",
816 current->comm, current->pid,
817 cattr_name(want_flags),
818 (unsigned long long)paddr,
819 (unsigned long long)(paddr + size),
824 * We allow returning different type than the one requested in
827 *vma_prot = __pgprot((pgprot_val(*vma_prot) &
828 (~_PAGE_CACHE_MASK)) |
832 if (kernel_map_sync_memtype(paddr, size, flags) < 0) {
833 free_memtype(paddr, paddr + size);
840 * Internal interface to free a range of physical memory.
841 * Frees non RAM regions only.
843 static void free_pfn_range(u64 paddr, unsigned long size)
847 is_ram = pat_pagerange_is_ram(paddr, paddr + size);
849 free_memtype(paddr, paddr + size);
853 * track_pfn_vma_copy is called when vma that is covering the pfnmap gets
854 * copied through copy_page_range().
856 * If the vma has a linear pfn mapping for the entire range, we get the prot
857 * from pte and reserve the entire vma range with single reserve_pfn_range call.
859 int track_pfn_vma_copy(struct vm_area_struct *vma)
861 resource_size_t paddr;
863 unsigned long vma_size = vma->vm_end - vma->vm_start;
866 if (is_linear_pfn_mapping(vma)) {
868 * reserve the whole chunk covered by vma. We need the
869 * starting address and protection from pte.
871 if (follow_phys(vma, vma->vm_start, 0, &prot, &paddr)) {
875 pgprot = __pgprot(prot);
876 return reserve_pfn_range(paddr, vma_size, &pgprot, 1);
883 * track_pfn_vma_new is called when a _new_ pfn mapping is being established
884 * for physical range indicated by pfn and size.
886 * prot is passed in as a parameter for the new mapping. If the vma has a
887 * linear pfn mapping for the entire range reserve the entire vma range with
888 * single reserve_pfn_range call.
890 int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
891 unsigned long pfn, unsigned long size)
894 resource_size_t paddr;
895 unsigned long vma_size = vma->vm_end - vma->vm_start;
897 if (is_linear_pfn_mapping(vma)) {
898 /* reserve the whole chunk starting from vm_pgoff */
899 paddr = (resource_size_t)vma->vm_pgoff << PAGE_SHIFT;
900 return reserve_pfn_range(paddr, vma_size, prot, 0);
906 /* for vm_insert_pfn and friends, we set prot based on lookup */
907 flags = lookup_memtype(pfn << PAGE_SHIFT);
908 *prot = __pgprot((pgprot_val(vma->vm_page_prot) & (~_PAGE_CACHE_MASK)) |
915 * untrack_pfn_vma is called while unmapping a pfnmap for a region.
916 * untrack can be called for a specific region indicated by pfn and size or
917 * can be for the entire vma (in which case size can be zero).
919 void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn,
922 resource_size_t paddr;
923 unsigned long vma_size = vma->vm_end - vma->vm_start;
925 if (is_linear_pfn_mapping(vma)) {
926 /* free the whole chunk starting from vm_pgoff */
927 paddr = (resource_size_t)vma->vm_pgoff << PAGE_SHIFT;
928 free_pfn_range(paddr, vma_size);
933 pgprot_t pgprot_writecombine(pgprot_t prot)
936 return __pgprot(pgprot_val(prot) | _PAGE_CACHE_WC);
938 return pgprot_noncached(prot);
940 EXPORT_SYMBOL_GPL(pgprot_writecombine);
942 #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
944 /* get Nth element of the linked list */
945 static struct memtype *memtype_get_idx(loff_t pos)
947 struct memtype *list_node, *print_entry;
950 print_entry = kmalloc(sizeof(struct memtype), GFP_KERNEL);
954 spin_lock(&memtype_lock);
955 list_for_each_entry(list_node, &memtype_list, nd) {
957 *print_entry = *list_node;
958 spin_unlock(&memtype_lock);
963 spin_unlock(&memtype_lock);
969 static void *memtype_seq_start(struct seq_file *seq, loff_t *pos)
973 seq_printf(seq, "PAT memtype list:\n");
976 return memtype_get_idx(*pos);
979 static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
982 return memtype_get_idx(*pos);
985 static void memtype_seq_stop(struct seq_file *seq, void *v)
989 static int memtype_seq_show(struct seq_file *seq, void *v)
991 struct memtype *print_entry = (struct memtype *)v;
993 seq_printf(seq, "%s @ 0x%Lx-0x%Lx\n", cattr_name(print_entry->type),
994 print_entry->start, print_entry->end);
1000 static const struct seq_operations memtype_seq_ops = {
1001 .start = memtype_seq_start,
1002 .next = memtype_seq_next,
1003 .stop = memtype_seq_stop,
1004 .show = memtype_seq_show,
1007 static int memtype_seq_open(struct inode *inode, struct file *file)
1009 return seq_open(file, &memtype_seq_ops);
1012 static const struct file_operations memtype_fops = {
1013 .open = memtype_seq_open,
1015 .llseek = seq_lseek,
1016 .release = seq_release,
1019 static int __init pat_memtype_list_init(void)
1021 debugfs_create_file("pat_memtype_list", S_IRUSR, arch_debugfs_dir,
1022 NULL, &memtype_fops);
1026 late_initcall(pat_memtype_list_init);
1028 #endif /* CONFIG_DEBUG_FS && CONFIG_X86_PAT */