1 files changed, 352 insertions, 260 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 06b7a1c90fb..738fd0f2495 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -7,30 +7,32 @@
  * Loosely based on earlier PAT patchset from Eric Biederman and Andi Kleen.
  */
 
-#include <linux/mm.h>
+#include <linux/seq_file.h>
+#include <linux/bootmem.h>
+#include <linux/debugfs.h>
 #include <linux/kernel.h>
 #include <linux/gfp.h>
+#include <linux/mm.h>
 #include <linux/fs.h>
-#include <linux/bootmem.h>
 
-#include <asm/msr.h>
-#include <asm/tlbflush.h>
+#include <asm/cacheflush.h>
 #include <asm/processor.h>
-#include <asm/page.h>
+#include <asm/tlbflush.h>
 #include <asm/pgtable.h>
-#include <asm/pat.h>
-#include <asm/e820.h>
-#include <asm/cacheflush.h>
 #include <asm/fcntl.h>
+#include <asm/e820.h>
 #include <asm/mtrr.h>
+#include <asm/page.h>
+#include <asm/msr.h>
+#include <asm/pat.h>
 #include <asm/io.h>
 
 #ifdef CONFIG_X86_PAT
-int __read_mostly pat_wc_enabled = 1;
+int __read_mostly pat_enabled = 1;
 
 void __cpuinit pat_disable(char *reason)
 {
-	pat_wc_enabled = 0;
+	pat_enabled = 0;
 	printk(KERN_INFO "%s\n", reason);
 }
 
@@ -42,6 +44,20 @@ static int __init nopat(char *str)
 early_param("nopat", nopat);
 #endif
 
+
+static int debug_enable;
+
+static int __init pat_debug_setup(char *str)
+{
+	debug_enable = 1;
+	return 0;
+}
+__setup("debugpat", pat_debug_setup);
+
+#define dprintk(fmt, arg...) \
+	do { if (debug_enable) printk(KERN_INFO fmt, ##arg); } while (0)
+
+
 static u64 __read_mostly boot_pat_state;
 
 enum {
@@ -53,24 +69,25 @@ enum {
 	PAT_UC_MINUS = 7,	/* UC, but can be overriden by MTRR */
 };
 
-#define PAT(x,y)	((u64)PAT_ ## y << ((x)*8))
+#define PAT(x, y)	((u64)PAT_ ## y << ((x)*8))
 
 void pat_init(void)
 {
 	u64 pat;
 
-	if (!pat_wc_enabled)
+	if (!pat_enabled)
 		return;
 
 	/* Paranoia check. */
-	if (!cpu_has_pat) {
-		printk(KERN_ERR "PAT enabled, but CPU feature cleared\n");
+	if (!cpu_has_pat && boot_pat_state) {
 		/*
-		 * Panic if this happens on the secondary CPU, and we
+		 * If this happens we are on a secondary CPU, but
 		 * switched to PAT on the boot CPU. We have no way to
 		 * undo PAT.
-		*/
-		BUG_ON(boot_pat_state);
+		 */
+		printk(KERN_ERR "PAT enabled, "
+		       "but not supported by secondary CPU\n");
+		BUG();
 	}
 
 	/* Set PWT to Write-Combining. All other bits stay the same */
@@ -86,8 +103,8 @@ void pat_init(void)
 	 *      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);
+	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 (!boot_pat_state)
@@ -103,11 +120,11 @@ void pat_init(void)
 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";
+	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";
 	}
 }
 
@@ -129,14 +146,14 @@ static char *cattr_name(unsigned long flags)
  */
 
 struct memtype {
-	u64 start;
-	u64 end;
-	unsigned long type;
-	struct list_head nd;
+	u64			start;
+	u64			end;
+	unsigned long		type;
+	struct list_head	nd;
 };
 
 static LIST_HEAD(memtype_list);
-static DEFINE_SPINLOCK(memtype_lock); 	/* protects memtype list */
+static DEFINE_SPINLOCK(memtype_lock);	/* protects memtype list */
 
 /*
  * Does intersection of PAT memory type and MTRR memory type and returns
@@ -145,47 +162,113 @@ static DEFINE_SPINLOCK(memtype_lock); 	/* protects memtype list */
  * 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)
+static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
 {
-	unsigned long pat_type;
-	u8 mtrr_type;
-
-	pat_type = prot & _PAGE_CACHE_MASK;
-	prot &= (~_PAGE_CACHE_MASK);
-
-	/*
-	 * We return the PAT request directly for types where PAT takes
-	 * precedence with respect to MTRR and for UC_MINUS.
-	 * Consistency checks with other PAT requests is done later
-	 * while going through memtype list.
-	 */
-	if (pat_type == _PAGE_CACHE_WC) {
-		*ret_prot = prot | _PAGE_CACHE_WC;
-		return 0;
-	} else if (pat_type == _PAGE_CACHE_UC_MINUS) {
-		*ret_prot = prot | _PAGE_CACHE_UC_MINUS;
-		return 0;
-	} else if (pat_type == _PAGE_CACHE_UC) {
-		*ret_prot = prot | _PAGE_CACHE_UC;
-		return 0;
-	}
-
 	/*
 	 * Look for MTRR hint to get the effective type in case where PAT
 	 * request is for WB.
 	 */
-	mtrr_type = mtrr_type_lookup(start, end);
+	if (req_type == _PAGE_CACHE_WB) {
+		u8 mtrr_type;
+
+		mtrr_type = mtrr_type_lookup(start, end);
+		if (mtrr_type == MTRR_TYPE_UNCACHABLE)
+			return _PAGE_CACHE_UC;
+		if (mtrr_type == MTRR_TYPE_WRCOMB)
+			return _PAGE_CACHE_WC;
+	}
 
-	if (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 req_type;
+}
+
+static int
+chk_conflict(struct memtype *new, struct memtype *entry, unsigned long *type)
+{
+	if (new->type != entry->type) {
+		if (type) {
+			new->type = entry->type;
+			*type = entry->type;
+		} else
+			goto conflict;
 	}
 
+	 /* check overlaps with more than one entry in the list */
+	list_for_each_entry_continue(entry, &memtype_list, nd) {
+		if (new->end <= entry->start)
+			break;
+		else if (new->type != entry->type)
+			goto conflict;
+	}
 	return 0;
+
+ conflict:
+	printk(KERN_INFO "%s:%d conflicting memory types "
+	       "%Lx-%Lx %s<->%s\n", current->comm, current->pid, new->start,
+	       new->end, cattr_name(new->type), cattr_name(entry->type));
+	return -EBUSY;
+}
+
+static struct memtype *cached_entry;
+static u64 cached_start;
+
+/*
+ * For RAM pages, mark the pages as non WB memory type using
+ * PageNonWB (PG_arch_1). We allow only one set_memory_uc() or
+ * set_memory_wc() on a RAM page at a time before marking it as WB again.
+ * This is ok, because only one driver will be owning the page and
+ * doing set_memory_*() calls.
+ *
+ * For now, we use PageNonWB to track that the RAM page is being mapped
+ * as non WB. In future, we will have to use one more flag
+ * (or some other mechanism in page_struct) to distinguish between
+ * UC and WC mapping.
+ */
+static int reserve_ram_pages_type(u64 start, u64 end, unsigned long req_type,
+				  unsigned long *new_type)
+{
+	struct page *page;
+	u64 pfn, end_pfn;
+
+	for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
+		page = pfn_to_page(pfn);
+		if (page_mapped(page) || PageNonWB(page))
+			goto out;
+
+		SetPageNonWB(page);
+	}
+	return 0;
+
+out:
+	end_pfn = pfn;
+	for (pfn = (start >> PAGE_SHIFT); pfn < end_pfn; ++pfn) {
+		page = pfn_to_page(pfn);
+		ClearPageNonWB(page);
+	}
+
+	return -EINVAL;
+}
+
+static int free_ram_pages_type(u64 start, u64 end)
+{
+	struct page *page;
+	u64 pfn, end_pfn;
+
+	for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
+		page = pfn_to_page(pfn);
+		if (page_mapped(page) || !PageNonWB(page))
+			goto out;
+
+		ClearPageNonWB(page);
+	}
+	return 0;
+
+out:
+	end_pfn = pfn;
+	for (pfn = (start >> PAGE_SHIFT); pfn < end_pfn; ++pfn) {
+		page = pfn_to_page(pfn);
+		SetPageNonWB(page);
+	}
+	return -EINVAL;
 }
 
 /*
@@ -198,37 +281,37 @@ static int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
  * 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
+ * If new_type is NULL, function will return an error if it cannot reserve the
+ * region with req_type. If new_type is non-NULL, function will return
+ * available type in new_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)
+		    unsigned long *new_type)
 {
-	struct memtype *new_entry = NULL;
-	struct memtype *parse;
+	struct memtype *new, *entry;
 	unsigned long actual_type;
+	struct list_head *where;
+	int is_range_ram;
 	int err = 0;
 
-	/* Only track when pat_wc_enabled */
-	if (!pat_wc_enabled) {
+	BUG_ON(start >= end); /* end is exclusive */
+
+	if (!pat_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;
-			}
+		if (new_type) {
+			if (req_type == -1)
+				*new_type = _PAGE_CACHE_WB;
+			else
+				*new_type = req_type & _PAGE_CACHE_MASK;
 		}
 		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;
-
+	if (is_ISA_range(start, end - 1)) {
+		if (new_type)
+			*new_type = _PAGE_CACHE_WB;
 		return 0;
 	}
 
@@ -241,206 +324,133 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
 		 */
 		u8 mtrr_type = mtrr_type_lookup(start, end);
 
-		if (mtrr_type == MTRR_TYPE_WRBACK) {
-			req_type = _PAGE_CACHE_WB;
+		if (mtrr_type == MTRR_TYPE_WRBACK)
 			actual_type = _PAGE_CACHE_WB;
-		} else {
-			req_type = _PAGE_CACHE_UC_MINUS;
+		else
 			actual_type = _PAGE_CACHE_UC_MINUS;
-		}
 	} else {
-		req_type &= _PAGE_CACHE_MASK;
-		err = pat_x_mtrr_type(start, end, req_type, &actual_type);
+		actual_type = pat_x_mtrr_type(start, end,
+					      req_type & _PAGE_CACHE_MASK);
 	}
 
-	if (err) {
-		if (ret_type)
-			*ret_type = actual_type;
-
+	is_range_ram = pagerange_is_ram(start, end);
+	if (is_range_ram == 1)
+		return reserve_ram_pages_type(start, end, req_type, new_type);
+	else if (is_range_ram < 0)
 		return -EINVAL;
-	}
 
-	new_entry  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
-	if (!new_entry)
+	new  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
+	if (!new)
 		return -ENOMEM;
 
-	new_entry->start = start;
-	new_entry->end = end;
-	new_entry->type = actual_type;
+	new->start	= start;
+	new->end	= end;
+	new->type	= actual_type;
 
-	if (ret_type)
-		*ret_type = actual_type;
+	if (new_type)
+		*new_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 (cached_entry && start >= cached_start)
+		entry = cached_entry;
+	else
+		entry = list_entry(&memtype_list, struct memtype, nd);
 
-		if (parse->start >= end) {
-			pr_debug("New Entry\n");
-			list_add(&new_entry->nd, parse->nd.prev);
-			new_entry = NULL;
+	/* Search for existing mapping that overlaps the current range */
+	where = NULL;
+	list_for_each_entry_continue(entry, &memtype_list, nd) {
+		if (end <= entry->start) {
+			where = entry->nd.prev;
+			cached_entry = list_entry(where, struct memtype, nd);
 			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;
+		} else if (start <= entry->start) { /* end > entry->start */
+			err = chk_conflict(new, entry, new_type);
+			if (!err) {
+				dprintk("Overlap at 0x%Lx-0x%Lx\n",
+					entry->start, entry->end);
+				where = entry->nd.prev;
+				cached_entry = list_entry(where,
+							struct memtype, nd);
 			}
-
-			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;
+		} else if (start < entry->end) { /* start > entry->start */
+			err = chk_conflict(new, entry, new_type);
+			if (!err) {
+				dprintk("Overlap at 0x%Lx-0x%Lx\n",
+					entry->start, entry->end);
+				cached_entry = list_entry(entry->nd.prev,
+							struct memtype, nd);
+
+				/*
+				 * Move to right position in the linked
+				 * list to add this new entry
+				 */
+				list_for_each_entry_continue(entry,
+							&memtype_list, nd) {
+					if (start <= entry->start) {
+						where = entry->nd.prev;
+						break;
+					}
 				}
 			}
-
-			if (err) {
-				break;
-			}
-
-			pr_debug(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);
+		printk(KERN_INFO "reserve_memtype failed 0x%Lx-0x%Lx, "
+		       "track %s, req %s\n",
+		       start, end, cattr_name(new->type), cattr_name(req_type));
+		kfree(new);
 		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");
-	}
+	cached_start = start;
 
-	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));
-	}
+	if (where)
+		list_add(&new->nd, where);
+	else
+		list_add_tail(&new->nd, &memtype_list);
 
 	spin_unlock(&memtype_lock);
+
+	dprintk("reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
+		start, end, cattr_name(new->type), cattr_name(req_type),
+		new_type ? cattr_name(*new_type) : "-");
+
 	return err;
 }
 
 int free_memtype(u64 start, u64 end)
 {
-	struct memtype *ml;
+	struct memtype *entry;
 	int err = -EINVAL;
+	int is_range_ram;
 
-	/* Only track when pat_wc_enabled */
-	if (!pat_wc_enabled) {
+	if (!pat_enabled)
 		return 0;
-	}
 
 	/* Low ISA region is always mapped WB. No need to track */
-	if (start >= ISA_START_ADDRESS && end <= ISA_END_ADDRESS) {
+	if (is_ISA_range(start, end - 1))
 		return 0;
-	}
+
+	is_range_ram = pagerange_is_ram(start, end);
+	if (is_range_ram == 1)
+		return free_ram_pages_type(start, end);
+	else if (is_range_ram < 0)
+		return -EINVAL;
 
 	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);
+	list_for_each_entry(entry, &memtype_list, nd) {
+		if (entry->start == start && entry->end == end) {
+			if (cached_entry == entry || cached_start == start)
+				cached_entry = NULL;
+
+			list_del(&entry->nd);
+			kfree(entry);
 			err = 0;
 			break;
 		}
@@ -452,27 +462,20 @@ int free_memtype(u64 start, u64 end)
 			current->comm, current->pid, start, end);
 	}
 
-	pr_debug("free_memtype request 0x%Lx-0x%Lx\n", start, end);
+	dprintk("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*/
+#ifdef CONFIG_STRICT_DEVMEM
+/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM*/
 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 {
 	return 1;
@@ -496,20 +499,20 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 	}
 	return 1;
 }
-#endif /* CONFIG_NONPROMISC_DEVMEM */
+#endif /* CONFIG_STRICT_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 flags = -1;
 	int retval;
 
 	if (!range_is_allowed(pfn, size))
 		return 0;
 
 	if (file->f_flags & O_SYNC) {
-		flags = _PAGE_CACHE_UC;
+		flags = _PAGE_CACHE_UC_MINUS;
 	}
 
 #ifdef CONFIG_X86_32
@@ -521,24 +524,25 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
 	 * 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)) {
+	if (!pat_enabled &&
+	    !(boot_cpu_has(X86_FEATURE_MTRR) ||
+	      boot_cpu_has(X86_FEATURE_K6_MTRR) ||
+	      boot_cpu_has(X86_FEATURE_CYRIX_ARR) ||
+	      boot_cpu_has(X86_FEATURE_CENTAUR_MCR)) &&
+	    (pfn << PAGE_SHIFT) >= __pa(high_memory)) {
 		flags = _PAGE_CACHE_UC;
 	}
 #endif
 
 	/*
-	 * With O_SYNC, we can only take UC mapping. Fail if we cannot.
+	 * With O_SYNC, we can only take UC_MINUS 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) {
+	if (flags != -1) {
 		retval = reserve_memtype(offset, offset + size, flags, NULL);
 	} else {
 		retval = reserve_memtype(offset, offset + size, -1, &flags);
@@ -547,8 +551,9 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
 	if (retval < 0)
 		return 0;
 
-	if (pfn <= max_pfn_mapped &&
-            ioremap_change_attr((unsigned long)__va(offset), size, flags) < 0) {
+	if (((pfn < max_low_pfn_mapped) ||
+	     (pfn >= (1UL<<(32 - PAGE_SHIFT)) && 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",
@@ -565,9 +570,9 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
 
 void map_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
 {
+	unsigned long want_flags = (pgprot_val(vma_prot) & _PAGE_CACHE_MASK);
 	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) {
@@ -587,3 +592,90 @@ void unmap_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
 	free_memtype(addr, addr + size);
 }
 
+#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
+
+/* get Nth element of the linked list */
+static struct memtype *memtype_get_idx(loff_t pos)
+{
+	struct memtype *list_node, *print_entry;
+	int i = 1;
+
+	print_entry  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
+	if (!print_entry)
+		return NULL;
+
+	spin_lock(&memtype_lock);
+	list_for_each_entry(list_node, &memtype_list, nd) {
+		if (pos == i) {
+			*print_entry = *list_node;
+			spin_unlock(&memtype_lock);
+			return print_entry;
+		}
+		++i;
+	}
+	spin_unlock(&memtype_lock);
+	kfree(print_entry);
+
+	return NULL;
+}
+
+static void *memtype_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	if (*pos == 0) {
+		++*pos;
+		seq_printf(seq, "PAT memtype list:\n");
+	}
+
+	return memtype_get_idx(*pos);
+}
+
+static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	++*pos;
+	return memtype_get_idx(*pos);
+}
+
+static void memtype_seq_stop(struct seq_file *seq, void *v)
+{
+}
+
+static int memtype_seq_show(struct seq_file *seq, void *v)
+{
+	struct memtype *print_entry = (struct memtype *)v;
+
+	seq_printf(seq, "%s @ 0x%Lx-0x%Lx\n", cattr_name(print_entry->type),
+			print_entry->start, print_entry->end);
+	kfree(print_entry);
+
+	return 0;
+}
+
+static struct seq_operations memtype_seq_ops = {
+	.start = memtype_seq_start,
+	.next  = memtype_seq_next,
+	.stop  = memtype_seq_stop,
+	.show  = memtype_seq_show,
+};
+
+static int memtype_seq_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &memtype_seq_ops);
+}
+
+static const struct file_operations memtype_fops = {
+	.open    = memtype_seq_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = seq_release,
+};
+
+static int __init pat_memtype_list_init(void)
+{
+	debugfs_create_file("pat_memtype_list", S_IRUSR, arch_debugfs_dir,
+				NULL, &memtype_fops);
+	return 0;
+}
+
+late_initcall(pat_memtype_list_init);
+
+#endif /* CONFIG_DEBUG_FS && CONFIG_X86_PAT */