Merge branch 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 core updates from Ingo Molnar:
 "There were so many changes in the x86/asm, x86/apic and x86/mm topics
  in this cycle that the topical separation of -tip broke down somewhat -
  so the result is a more traditional architecture pull request,
  collected into the 'x86/core' topic.

  The topics were still maintained separately as far as possible, so
  bisectability and conceptual separation should still be pretty good -
  but there were a handful of merge points to avoid excessive
  dependencies (and conflicts) that would have been poorly tested in the
  end.

  The next cycle will hopefully be much more quiet (or at least will
  have fewer dependencies).

  The main changes in this cycle were:

   * x86/apic changes, with related IRQ core changes: (Jiang Liu, Thomas
     Gleixner)

     - This is the second and most intrusive part of changes to the x86
       interrupt handling - full conversion to hierarchical interrupt
       domains:

          [IOAPIC domain]   -----
                                 |
          [MSI domain]      --------[Remapping domain] ----- [ Vector domain ]
                                 |   (optional)          |
          [HPET MSI domain] -----                        |
                                                         |
          [DMAR domain]     -----------------------------
                                                         |
          [Legacy domain]   -----------------------------

       This now reflects the actual hardware and allowed us to distangle
       the domain specific code from the underlying parent domain, which
       can be optional in the case of interrupt remapping.  It's a clear
       separation of functionality and removes quite some duct tape
       constructs which plugged the remap code between ioapic/msi/hpet
       and the vector management.

     - Intel IOMMU IRQ remapping enhancements, to allow direct interrupt
       injection into guests (Feng Wu)

   * x86/asm changes:

     - Tons of cleanups and small speedups, micro-optimizations.  This
       is in preparation to move a good chunk of the low level entry
       code from assembly to C code (Denys Vlasenko, Andy Lutomirski,
       Brian Gerst)

     - Moved all system entry related code to a new home under
       arch/x86/entry/ (Ingo Molnar)

     - Removal of the fragile and ugly CFI dwarf debuginfo annotations.
       Conversion to C will reintroduce many of them - but meanwhile
       they are only getting in the way, and the upstream kernel does
       not rely on them (Ingo Molnar)

     - NOP handling refinements. (Borislav Petkov)

   * x86/mm changes:

     - Big PAT and MTRR rework: making the code more robust and
       preparing to phase out exposing direct MTRR interfaces to drivers -
       in favor of using PAT driven interfaces (Toshi Kani, Luis R
       Rodriguez, Borislav Petkov)

     - New ioremap_wt()/set_memory_wt() interfaces to support
       Write-Through cached memory mappings.  This is especially
       important for good performance on NVDIMM hardware (Toshi Kani)

   * x86/ras changes:

     - Add support for deferred errors on AMD (Aravind Gopalakrishnan)

       This is an important RAS feature which adds hardware support for
       poisoned data.  That means roughly that the hardware marks data
       which it has detected as corrupted but wasn't able to correct, as
       poisoned data and raises an APIC interrupt to signal that in the
       form of a deferred error.  It is the OS's responsibility then to
       take proper recovery action and thus prolonge system lifetime as
       far as possible.

     - Add support for Intel "Local MCE"s: upcoming CPUs will support
       CPU-local MCE interrupts, as opposed to the traditional system-
       wide broadcasted MCE interrupts (Ashok Raj)

     - Misc cleanups (Borislav Petkov)

   * x86/platform changes:

     - Intel Atom SoC updates

  ... and lots of other cleanups, fixlets and other changes - see the
  shortlog and the Git log for details"

* 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (222 commits)
  x86/hpet: Use proper hpet device number for MSI allocation
  x86/hpet: Check for irq==0 when allocating hpet MSI interrupts
  x86/mm/pat, drivers/infiniband/ipath: Use arch_phys_wc_add() and require PAT disabled
  x86/mm/pat, drivers/media/ivtv: Use arch_phys_wc_add() and require PAT disabled
  x86/platform/intel/baytrail: Add comments about why we disabled HPET on Baytrail
  genirq: Prevent crash in irq_move_irq()
  genirq: Enhance irq_data_to_desc() to support hierarchy irqdomain
  iommu, x86: Properly handle posted interrupts for IOMMU hotplug
  iommu, x86: Provide irq_remapping_cap() interface
  iommu, x86: Setup Posted-Interrupts capability for Intel iommu
  iommu, x86: Add cap_pi_support() to detect VT-d PI capability
  iommu, x86: Avoid migrating VT-d posted interrupts
  iommu, x86: Save the mode (posted or remapped) of an IRTE
  iommu, x86: Implement irq_set_vcpu_affinity for intel_ir_chip
  iommu: dmar: Provide helper to copy shared irte fields
  iommu: dmar: Extend struct irte for VT-d Posted-Interrupts
  iommu: Add new member capability to struct irq_remap_ops
  x86/asm/entry/64: Disentangle error_entry/exit gsbase/ebx/usermode code
  x86/asm/entry/32: Shorten __audit_syscall_entry() args preparation
  x86/asm/entry/32: Explain reloading of registers after __audit_syscall_entry()
  ...

9 files changed, 393 insertions, 186 deletions

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1d55318..8533b46 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -40,7 +40,7 @@
  */
 uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = {
 	[_PAGE_CACHE_MODE_WB      ]	= 0         | 0        ,
-	[_PAGE_CACHE_MODE_WC      ]	= _PAGE_PWT | 0        ,
+	[_PAGE_CACHE_MODE_WC      ]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC_MINUS]	= 0         | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_UC      ]	= _PAGE_PWT | _PAGE_PCD,
 	[_PAGE_CACHE_MODE_WT      ]	= 0         | _PAGE_PCD,
@@ -50,11 +50,11 @@ EXPORT_SYMBOL(__cachemode2pte_tbl);
 
 uint8_t __pte2cachemode_tbl[8] = {
 	[__pte2cm_idx( 0        | 0         | 0        )] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx( 0        | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC,
 	[__pte2cm_idx( 0        | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
-	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
+	[__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(0         | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
 	[__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
 };
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index 2b7ece0..9c0ff04 100644
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -78,13 +78,13 @@ void __iomem *
 iomap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
 {
 	/*
-	 * For non-PAT systems, promote PAGE_KERNEL_WC to PAGE_KERNEL_UC_MINUS.
-	 * PAGE_KERNEL_WC maps to PWT, which translates to uncached if the
-	 * MTRR is UC or WC.  UC_MINUS gets the real intention, of the
-	 * user, which is "WC if the MTRR is WC, UC if you can't do that."
+	 * For non-PAT systems, translate non-WB request to UC- just in
+	 * case the caller set the PWT bit to prot directly without using
+	 * pgprot_writecombine(). UC- translates to uncached if the MTRR
+	 * is UC or WC. UC- gets the real intention, of the user, which is
+	 * "WC if the MTRR is WC, UC if you can't do that."
 	 */
-	if (!pat_enabled && pgprot_val(prot) ==
-	    (__PAGE_KERNEL | cachemode2protval(_PAGE_CACHE_MODE_WC)))
+	if (!pat_enabled() && pgprot2cachemode(prot) != _PAGE_CACHE_MODE_WB)
 		prot = __pgprot(__PAGE_KERNEL |
 				cachemode2protval(_PAGE_CACHE_MODE_UC_MINUS));
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 27ff212..cc5ccc4 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -42,6 +42,9 @@ int ioremap_change_attr(unsigned long vaddr, unsigned long size,
 	case _PAGE_CACHE_MODE_WC:
 		err = _set_memory_wc(vaddr, nrpages);
 		break;
+	case _PAGE_CACHE_MODE_WT:
+		err = _set_memory_wt(vaddr, nrpages);
+		break;
 	case _PAGE_CACHE_MODE_WB:
 		err = _set_memory_wb(vaddr, nrpages);
 		break;
@@ -172,6 +175,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 		prot = __pgprot(pgprot_val(prot) |
 				cachemode2protval(_PAGE_CACHE_MODE_WC));
 		break;
+	case _PAGE_CACHE_MODE_WT:
+		prot = __pgprot(pgprot_val(prot) |
+				cachemode2protval(_PAGE_CACHE_MODE_WT));
+		break;
 	case _PAGE_CACHE_MODE_WB:
 		break;
 	}
@@ -234,10 +241,11 @@ void __iomem *ioremap_nocache(resource_size_t phys_addr, unsigned long size)
 {
 	/*
 	 * Ideally, this should be:
-	 *	pat_enabled ? _PAGE_CACHE_MODE_UC : _PAGE_CACHE_MODE_UC_MINUS;
+	 *	pat_enabled() ? _PAGE_CACHE_MODE_UC : _PAGE_CACHE_MODE_UC_MINUS;
 	 *
 	 * Till we fix all X drivers to use ioremap_wc(), we will use
-	 * UC MINUS.
+	 * UC MINUS. Drivers that are certain they need or can already
+	 * be converted over to strong UC can use ioremap_uc().
 	 */
 	enum page_cache_mode pcm = _PAGE_CACHE_MODE_UC_MINUS;
 
@@ -247,6 +255,39 @@ void __iomem *ioremap_nocache(resource_size_t phys_addr, unsigned long size)
 EXPORT_SYMBOL(ioremap_nocache);
 
 /**
+ * ioremap_uc     -   map bus memory into CPU space as strongly uncachable
+ * @phys_addr:    bus address of the memory
+ * @size:      size of the resource to map
+ *
+ * ioremap_uc performs a platform specific sequence of operations to
+ * make bus memory CPU accessible via the readb/readw/readl/writeb/
+ * writew/writel functions and the other mmio helpers. The returned
+ * address is not guaranteed to be usable directly as a virtual
+ * address.
+ *
+ * This version of ioremap ensures that the memory is marked with a strong
+ * preference as completely uncachable on the CPU when possible. For non-PAT
+ * systems this ends up setting page-attribute flags PCD=1, PWT=1. For PAT
+ * systems this will set the PAT entry for the pages as strong UC.  This call
+ * will honor existing caching rules from things like the PCI bus. Note that
+ * there are other caches and buffers on many busses. In particular driver
+ * authors should read up on PCI writes.
+ *
+ * It's useful if some control registers are in such an area and
+ * write combining or read caching is not desirable:
+ *
+ * Must be freed with iounmap.
+ */
+void __iomem *ioremap_uc(resource_size_t phys_addr, unsigned long size)
+{
+	enum page_cache_mode pcm = _PAGE_CACHE_MODE_UC;
+
+	return __ioremap_caller(phys_addr, size, pcm,
+				__builtin_return_address(0));
+}
+EXPORT_SYMBOL_GPL(ioremap_uc);
+
+/**
  * ioremap_wc	-	map memory into CPU space write combined
  * @phys_addr:	bus address of the memory
  * @size:	size of the resource to map
@@ -258,14 +299,28 @@ EXPORT_SYMBOL(ioremap_nocache);
  */
 void __iomem *ioremap_wc(resource_size_t phys_addr, unsigned long size)
 {
-	if (pat_enabled)
-		return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WC,
+	return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WC,
 					__builtin_return_address(0));
-	else
-		return ioremap_nocache(phys_addr, size);
 }
 EXPORT_SYMBOL(ioremap_wc);
 
+/**
+ * ioremap_wt	-	map memory into CPU space write through
+ * @phys_addr:	bus address of the memory
+ * @size:	size of the resource to map
+ *
+ * This version of ioremap ensures that the memory is marked write through.
+ * Write through stores data into memory while keeping the cache up-to-date.
+ *
+ * Must be freed with iounmap.
+ */
+void __iomem *ioremap_wt(resource_size_t phys_addr, unsigned long size)
+{
+	return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WT,
+					__builtin_return_address(0));
+}
+EXPORT_SYMBOL(ioremap_wt);
+
 void __iomem *ioremap_cache(resource_size_t phys_addr, unsigned long size)
 {
 	return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WB,
@@ -331,7 +386,7 @@ void iounmap(volatile void __iomem *addr)
 }
 EXPORT_SYMBOL(iounmap);
 
-int arch_ioremap_pud_supported(void)
+int __init arch_ioremap_pud_supported(void)
 {
 #ifdef CONFIG_X86_64
 	return cpu_has_gbpages;
@@ -340,7 +395,7 @@ int arch_ioremap_pud_supported(void)
 #endif
 }
 
-int arch_ioremap_pmd_supported(void)
+int __init arch_ioremap_pmd_supported(void)
 {
 	return cpu_has_pse;
 }
diff --git a/arch/x86/mm/pageattr-test.c b/arch/x86/mm/pageattr-test.c
index 6629f39..8ff686a 100644
--- a/arch/x86/mm/pageattr-test.c
+++ b/arch/x86/mm/pageattr-test.c
@@ -9,6 +9,7 @@
 #include <linux/random.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
+#include <linux/vmalloc.h>
 
 #include <asm/cacheflush.h>
 #include <asm/pgtable.h>
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 89af288..727158c 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -14,6 +14,7 @@
 #include <linux/percpu.h>
 #include <linux/gfp.h>
 #include <linux/pci.h>
+#include <linux/vmalloc.h>
 
 #include <asm/e820.h>
 #include <asm/processor.h>
@@ -129,16 +130,15 @@ within(unsigned long addr, unsigned long start, unsigned long end)
  */
 void clflush_cache_range(void *vaddr, unsigned int size)
 {
-	void *vend = vaddr + size - 1;
+	unsigned long clflush_mask = boot_cpu_data.x86_clflush_size - 1;
+	void *vend = vaddr + size;
+	void *p;
 
 	mb();
 
-	for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
-		clflushopt(vaddr);
-	/*
-	 * Flush any possible final partial cacheline:
-	 */
-	clflushopt(vend);
+	for (p = (void *)((unsigned long)vaddr & ~clflush_mask);
+	     p < vend; p += boot_cpu_data.x86_clflush_size)
+		clflushopt(p);
 
 	mb();
 }
@@ -418,13 +418,11 @@ phys_addr_t slow_virt_to_phys(void *__virt_addr)
 	phys_addr_t phys_addr;
 	unsigned long offset;
 	enum pg_level level;
-	unsigned long psize;
 	unsigned long pmask;
 	pte_t *pte;
 
 	pte = lookup_address(virt_addr, &level);
 	BUG_ON(!pte);
-	psize = page_level_size(level);
 	pmask = page_level_mask(level);
 	offset = virt_addr & ~pmask;
 	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
@@ -1468,6 +1466,9 @@ int _set_memory_uc(unsigned long addr, int numpages)
 {
 	/*
 	 * for now UC MINUS. see comments in ioremap_nocache()
+	 * If you really need strong UC use ioremap_uc(), but note
+	 * that you cannot override IO areas with set_memory_*() as
+	 * these helpers cannot work with IO memory.
 	 */
 	return change_page_attr_set(&addr, numpages,
 				    cachemode2pgprot(_PAGE_CACHE_MODE_UC_MINUS),
@@ -1502,12 +1503,10 @@ EXPORT_SYMBOL(set_memory_uc);
 static int _set_memory_array(unsigned long *addr, int addrinarray,
 		enum page_cache_mode new_type)
 {
+	enum page_cache_mode set_type;
 	int i, j;
 	int ret;
 
-	/*
-	 * for now UC MINUS. see comments in ioremap_nocache()
-	 */
 	for (i = 0; i < addrinarray; i++) {
 		ret = reserve_memtype(__pa(addr[i]), __pa(addr[i]) + PAGE_SIZE,
 					new_type, NULL);
@@ -1515,9 +1514,12 @@ static int _set_memory_array(unsigned long *addr, int addrinarray,
 			goto out_free;
 	}
 
+	/* If WC, set to UC- first and then WC */
+	set_type = (new_type == _PAGE_CACHE_MODE_WC) ?
+				_PAGE_CACHE_MODE_UC_MINUS : new_type;
+
 	ret = change_page_attr_set(addr, addrinarray,
-				   cachemode2pgprot(_PAGE_CACHE_MODE_UC_MINUS),
-				   1);
+				   cachemode2pgprot(set_type), 1);
 
 	if (!ret && new_type == _PAGE_CACHE_MODE_WC)
 		ret = change_page_attr_set_clr(addr, addrinarray,
@@ -1549,6 +1551,12 @@ int set_memory_array_wc(unsigned long *addr, int addrinarray)
 }
 EXPORT_SYMBOL(set_memory_array_wc);
 
+int set_memory_array_wt(unsigned long *addr, int addrinarray)
+{
+	return _set_memory_array(addr, addrinarray, _PAGE_CACHE_MODE_WT);
+}
+EXPORT_SYMBOL_GPL(set_memory_array_wt);
+
 int _set_memory_wc(unsigned long addr, int numpages)
 {
 	int ret;
@@ -1571,27 +1579,42 @@ int set_memory_wc(unsigned long addr, int numpages)
 {
 	int ret;
 
-	if (!pat_enabled)
-		return set_memory_uc(addr, numpages);
-
 	ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
 		_PAGE_CACHE_MODE_WC, NULL);
 	if (ret)
-		goto out_err;
+		return ret;
 
 	ret = _set_memory_wc(addr, numpages);
 	if (ret)
-		goto out_free;
-
-	return 0;
+		free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
 
-out_free:
-	free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
-out_err:
 	return ret;
 }
 EXPORT_SYMBOL(set_memory_wc);
 
+int _set_memory_wt(unsigned long addr, int numpages)
+{
+	return change_page_attr_set(&addr, numpages,
+				    cachemode2pgprot(_PAGE_CACHE_MODE_WT), 0);
+}
+
+int set_memory_wt(unsigned long addr, int numpages)
+{
+	int ret;
+
+	ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
+			      _PAGE_CACHE_MODE_WT, NULL);
+	if (ret)
+		return ret;
+
+	ret = _set_memory_wt(addr, numpages);
+	if (ret)
+		free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(set_memory_wt);
+
 int _set_memory_wb(unsigned long addr, int numpages)
 {
 	/* WB cache mode is hard wired to all cache attribute bits being 0 */
@@ -1682,6 +1705,7 @@ static int _set_pages_array(struct page **pages, int addrinarray,
 {
 	unsigned long start;
 	unsigned long end;
+	enum page_cache_mode set_type;
 	int i;
 	int free_idx;
 	int ret;
@@ -1695,8 +1719,12 @@ static int _set_pages_array(struct page **pages, int addrinarray,
 			goto err_out;
 	}
 
+	/* If WC, set to UC- first and then WC */
+	set_type = (new_type == _PAGE_CACHE_MODE_WC) ?
+				_PAGE_CACHE_MODE_UC_MINUS : new_type;
+
 	ret = cpa_set_pages_array(pages, addrinarray,
-			cachemode2pgprot(_PAGE_CACHE_MODE_UC_MINUS));
+				  cachemode2pgprot(set_type));
 	if (!ret && new_type == _PAGE_CACHE_MODE_WC)
 		ret = change_page_attr_set_clr(NULL, addrinarray,
 					       cachemode2pgprot(
@@ -1730,6 +1758,12 @@ int set_pages_array_wc(struct page **pages, int addrinarray)
 }
 EXPORT_SYMBOL(set_pages_array_wc);
 
+int set_pages_array_wt(struct page **pages, int addrinarray)
+{
+	return _set_pages_array(pages, addrinarray, _PAGE_CACHE_MODE_WT);
+}
+EXPORT_SYMBOL_GPL(set_pages_array_wt);
+
 int set_pages_wb(struct page *page, int numpages)
 {
 	unsigned long addr = (unsigned long)page_address(page);
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 35af677..188e3e0 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -33,13 +33,17 @@
 #include "pat_internal.h"
 #include "mm_internal.h"
 
-#ifdef CONFIG_X86_PAT
-int __read_mostly pat_enabled = 1;
+#undef pr_fmt
+#define pr_fmt(fmt) "" fmt
+
+static bool boot_cpu_done;
+
+static int __read_mostly __pat_enabled = IS_ENABLED(CONFIG_X86_PAT);
 
 static inline void pat_disable(const char *reason)
 {
-	pat_enabled = 0;
-	printk(KERN_INFO "%s\n", reason);
+	__pat_enabled = 0;
+	pr_info("x86/PAT: %s\n", reason);
 }
 
 static int __init nopat(char *str)
@@ -48,13 +52,12 @@ static int __init nopat(char *str)
 	return 0;
 }
 early_param("nopat", nopat);
-#else
-static inline void pat_disable(const char *reason)
+
+bool pat_enabled(void)
 {
-	(void)reason;
+	return !!__pat_enabled;
 }
-#endif
-
+EXPORT_SYMBOL_GPL(pat_enabled);
 
 int pat_debug_enable;
 
@@ -65,22 +68,24 @@ static int __init pat_debug_setup(char *str)
 }
 __setup("debugpat", pat_debug_setup);
 
-static u64 __read_mostly boot_pat_state;
-
 #ifdef CONFIG_X86_PAT
 /*
- * X86 PAT uses page flags WC and Uncached together to keep track of
- * memory type of pages that have backing page struct. X86 PAT supports 3
- * different memory types, _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC and
- * _PAGE_CACHE_MODE_UC_MINUS and fourth state where page's memory type has not
- * been changed from its default (value of -1 used to denote this).
- * Note we do not support _PAGE_CACHE_MODE_UC here.
+ * X86 PAT uses page flags arch_1 and uncached together to keep track of
+ * memory type of pages that have backing page struct.
+ *
+ * X86 PAT supports 4 different memory types:
+ *  - _PAGE_CACHE_MODE_WB
+ *  - _PAGE_CACHE_MODE_WC
+ *  - _PAGE_CACHE_MODE_UC_MINUS
+ *  - _PAGE_CACHE_MODE_WT
+ *
+ * _PAGE_CACHE_MODE_WB is the default type.
  */
 
-#define _PGMT_DEFAULT		0
+#define _PGMT_WB		0
 #define _PGMT_WC		(1UL << PG_arch_1)
 #define _PGMT_UC_MINUS		(1UL << PG_uncached)
-#define _PGMT_WB		(1UL << PG_uncached | 1UL << PG_arch_1)
+#define _PGMT_WT		(1UL << PG_uncached | 1UL << PG_arch_1)
 #define _PGMT_MASK		(1UL << PG_uncached | 1UL << PG_arch_1)
 #define _PGMT_CLEAR_MASK	(~_PGMT_MASK)
 
@@ -88,14 +93,14 @@ static inline enum page_cache_mode get_page_memtype(struct page *pg)
 {
 	unsigned long pg_flags = pg->flags & _PGMT_MASK;
 
-	if (pg_flags == _PGMT_DEFAULT)
-		return -1;
+	if (pg_flags == _PGMT_WB)
+		return _PAGE_CACHE_MODE_WB;
 	else if (pg_flags == _PGMT_WC)
 		return _PAGE_CACHE_MODE_WC;
 	else if (pg_flags == _PGMT_UC_MINUS)
 		return _PAGE_CACHE_MODE_UC_MINUS;
 	else
-		return _PAGE_CACHE_MODE_WB;
+		return _PAGE_CACHE_MODE_WT;
 }
 
 static inline void set_page_memtype(struct page *pg,
@@ -112,11 +117,12 @@ static inline void set_page_memtype(struct page *pg,
 	case _PAGE_CACHE_MODE_UC_MINUS:
 		memtype_flags = _PGMT_UC_MINUS;
 		break;
-	case _PAGE_CACHE_MODE_WB:
-		memtype_flags = _PGMT_WB;
+	case _PAGE_CACHE_MODE_WT:
+		memtype_flags = _PGMT_WT;
 		break;
+	case _PAGE_CACHE_MODE_WB:
 	default:
-		memtype_flags = _PGMT_DEFAULT;
+		memtype_flags = _PGMT_WB;
 		break;
 	}
 
@@ -174,78 +180,154 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
  * configuration.
  * Using lower indices is preferred, so we start with highest index.
  */
-void pat_init_cache_modes(void)
+void pat_init_cache_modes(u64 pat)
 {
-	int i;
 	enum page_cache_mode cache;
 	char pat_msg[33];
-	u64 pat;
+	int i;
 
-	rdmsrl(MSR_IA32_CR_PAT, pat);
 	pat_msg[32] = 0;
 	for (i = 7; i >= 0; i--) {
 		cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
 					   pat_msg + 4 * i);
 		update_cache_mode_entry(i, cache);
 	}
-	pr_info("PAT configuration [0-7]: %s\n", pat_msg);
+	pr_info("x86/PAT: Configuration [0-7]: %s\n", pat_msg);
 }
 
 #define PAT(x, y)	((u64)PAT_ ## y << ((x)*8))
 
-void pat_init(void)
+static void pat_bsp_init(u64 pat)
 {
-	u64 pat;
-	bool boot_cpu = !boot_pat_state;
+	u64 tmp_pat;
 
-	if (!pat_enabled)
+	if (!cpu_has_pat) {
+		pat_disable("PAT not supported by CPU.");
 		return;
+	}
 
-	if (!cpu_has_pat) {
-		if (!boot_pat_state) {
-			pat_disable("PAT not supported by CPU.");
-			return;
-		} else {
-			/*
-			 * If this happens we are on a secondary CPU, but
-			 * switched to PAT on the boot CPU. We have no way to
-			 * undo PAT.
-			 */
-			printk(KERN_ERR "PAT enabled, "
-			       "but not supported by secondary CPU\n");
-			BUG();
-		}
+	if (!pat_enabled())
+		goto done;
+
+	rdmsrl(MSR_IA32_CR_PAT, tmp_pat);
+	if (!tmp_pat) {
+		pat_disable("PAT MSR is 0, disabled.");
+		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 (!boot_pat_state) {
-		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
-		if (!boot_pat_state) {
-			pat_disable("PAT read returns always zero, disabled.");
-			return;
-		}
+	wrmsrl(MSR_IA32_CR_PAT, pat);
+
+done:
+	pat_init_cache_modes(pat);
+}
+
+static void pat_ap_init(u64 pat)
+{
+	if (!pat_enabled())
+		return;
+
+	if (!cpu_has_pat) {
+		/*
+		 * If this happens we are on a secondary CPU, but switched to
+		 * PAT on the boot CPU. We have no way to undo PAT.
+		 */
+		panic("x86/PAT: PAT enabled, but not supported by secondary CPU\n");
 	}
 
 	wrmsrl(MSR_IA32_CR_PAT, pat);
+}
+
+void pat_init(void)
+{
+	u64 pat;
+	struct cpuinfo_x86 *c = &boot_cpu_data;
+
+	if (!pat_enabled()) {
+		/*
+		 * No PAT. Emulate the PAT table that corresponds to the two
+		 * cache bits, PWT (Write Through) and PCD (Cache Disable). This
+		 * setup is the same as the BIOS default setup when the system
+		 * has PAT but the "nopat" boot option has been specified. This
+		 * emulated PAT table is used when MSR_IA32_CR_PAT returns 0.
+		 *
+		 * PTE encoding:
+		 *
+		 *       PCD
+		 *       |PWT  PAT
+		 *       ||    slot
+		 *       00    0    WB : _PAGE_CACHE_MODE_WB
+		 *       01    1    WT : _PAGE_CACHE_MODE_WT
+		 *       10    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *       11    3    UC : _PAGE_CACHE_MODE_UC
+		 *
+		 * NOTE: When WC or WP is used, it is redirected to UC- per
+		 * the default setup in __cachemode2pte_tbl[].
+		 */
+		pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
+		      PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
 
-	if (boot_cpu)
-		pat_init_cache_modes();
+	} else if ((c->x86_vendor == X86_VENDOR_INTEL) &&
+		   (((c->x86 == 0x6) && (c->x86_model <= 0xd)) ||
+		    ((c->x86 == 0xf) && (c->x86_model <= 0x6)))) {
+		/*
+		 * PAT support with the lower four entries. Intel Pentium 2,
+		 * 3, M, and 4 are affected by PAT errata, which makes the
+		 * upper four entries unusable. To be on the safe side, we don't
+		 * use those.
+		 *
+		 *  PTE encoding:
+		 *      PAT
+		 *      |PCD
+		 *      ||PWT  PAT
+		 *      |||    slot
+		 *      000    0    WB : _PAGE_CACHE_MODE_WB
+		 *      001    1    WC : _PAGE_CACHE_MODE_WC
+		 *      010    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *      011    3    UC : _PAGE_CACHE_MODE_UC
+		 * PAT bit unused
+		 *
+		 * NOTE: When WT or WP is used, it is redirected to UC- per
+		 * the default setup in __cachemode2pte_tbl[].
+		 */
+		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);
+	} else {
+		/*
+		 * Full PAT support.  We put WT in slot 7 to improve
+		 * robustness in the presence of errata that might cause
+		 * the high PAT bit to be ignored.  This way, a buggy slot 7
+		 * access will hit slot 3, and slot 3 is UC, so at worst
+		 * we lose performance without causing a correctness issue.
+		 * Pentium 4 erratum N46 is an example for such an erratum,
+		 * although we try not to use PAT at all on affected CPUs.
+		 *
+		 *  PTE encoding:
+		 *      PAT
+		 *      |PCD
+		 *      ||PWT  PAT
+		 *      |||    slot
+		 *      000    0    WB : _PAGE_CACHE_MODE_WB
+		 *      001    1    WC : _PAGE_CACHE_MODE_WC
+		 *      010    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
+		 *      011    3    UC : _PAGE_CACHE_MODE_UC
+		 *      100    4    WB : Reserved
+		 *      101    5    WC : Reserved
+		 *      110    6    UC-: Reserved
+		 *      111    7    WT : _PAGE_CACHE_MODE_WT
+		 *
+		 * The reserved slots are unused, but mapped to their
+		 * corresponding types in the presence of PAT errata.
+		 */
+		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, WT);
+	}
+
+	if (!boot_cpu_done) {
+		pat_bsp_init(pat);
+		boot_cpu_done = true;
+	} else {
+		pat_ap_init(pat);
+	}
 }
 
 #undef PAT
@@ -267,9 +349,9 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end,
 	 * request is for WB.
 	 */
 	if (req_type == _PAGE_CACHE_MODE_WB) {
-		u8 mtrr_type;
+		u8 mtrr_type, uniform;
 
-		mtrr_type = mtrr_type_lookup(start, end);
+		mtrr_type = mtrr_type_lookup(start, end, &uniform);
 		if (mtrr_type != MTRR_TYPE_WRBACK)
 			return _PAGE_CACHE_MODE_UC_MINUS;
 
@@ -324,9 +406,14 @@ static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end)
 
 /*
  * For RAM pages, we use page flags to mark the pages with appropriate type.
- * Here we do two pass:
- * - Find the memtype of all the pages in the range, look for any conflicts
- * - In case of no conflicts, set the new memtype for pages in the range
+ * The page flags are limited to four types, WB (default), WC, WT and UC-.
+ * WP request fails with -EINVAL, and UC gets redirected to UC-.  Setting
+ * a new memory type is only allowed for a page mapped with the default WB
+ * type.
+ *
+ * Here we do two passes:
+ * - Find the memtype of all the pages in the range, look for any conflicts.
+ * - In case of no conflicts, set the new memtype for pages in the range.
  */
 static int reserve_ram_pages_type(u64 start, u64 end,
 				  enum page_cache_mode req_type,
@@ -335,6 +422,12 @@ static int reserve_ram_pages_type(u64 start, u64 end,
 	struct page *page;
 	u64 pfn;
 
+	if (req_type == _PAGE_CACHE_MODE_WP) {
+		if (new_type)
+			*new_type = _PAGE_CACHE_MODE_UC_MINUS;
+		return -EINVAL;
+	}
+
 	if (req_type == _PAGE_CACHE_MODE_UC) {
 		/* We do not support strong UC */
 		WARN_ON_ONCE(1);
@@ -346,8 +439,8 @@ static int reserve_ram_pages_type(u64 start, u64 end,
 
 		page = pfn_to_page(pfn);
 		type = get_page_memtype(page);
-		if (type != -1) {
-			pr_info("reserve_ram_pages_type failed [mem %#010Lx-%#010Lx], track 0x%x, req 0x%x\n",
+		if (type != _PAGE_CACHE_MODE_WB) {
+			pr_info("x86/PAT: reserve_ram_pages_type failed [mem %#010Lx-%#010Lx], track 0x%x, req 0x%x\n",
 				start, end - 1, type, req_type);
 			if (new_type)
 				*new_type = type;
@@ -373,7 +466,7 @@ static int free_ram_pages_type(u64 start, u64 end)
 
 	for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
 		page = pfn_to_page(pfn);
-		set_page_memtype(page, -1);
+		set_page_memtype(page, _PAGE_CACHE_MODE_WB);
 	}
 	return 0;
 }
@@ -384,6 +477,7 @@ static int free_ram_pages_type(u64 start, u64 end)
  * - _PAGE_CACHE_MODE_WC
  * - _PAGE_CACHE_MODE_UC_MINUS
  * - _PAGE_CACHE_MODE_UC
+ * - _PAGE_CACHE_MODE_WT
  *
  * 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
@@ -400,14 +494,10 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
 
 	BUG_ON(start >= end); /* end is exclusive */
 
-	if (!pat_enabled) {
+	if (!pat_enabled()) {
 		/* This is identical to page table setting without PAT */
-		if (new_type) {
-			if (req_type == _PAGE_CACHE_MODE_WC)
-				*new_type = _PAGE_CACHE_MODE_UC_MINUS;
-			else
-				*new_type = req_type;
-		}
+		if (new_type)
+			*new_type = req_type;
 		return 0;
 	}
 
@@ -451,9 +541,9 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
 
 	err = rbt_memtype_check_insert(new, new_type);
 	if (err) {
-		printk(KERN_INFO "reserve_memtype failed [mem %#010Lx-%#010Lx], track %s, req %s\n",
-		       start, end - 1,
-		       cattr_name(new->type), cattr_name(req_type));
+		pr_info("x86/PAT: reserve_memtype failed [mem %#010Lx-%#010Lx], track %s, req %s\n",
+			start, end - 1,
+			cattr_name(new->type), cattr_name(req_type));
 		kfree(new);
 		spin_unlock(&memtype_lock);
 
@@ -475,7 +565,7 @@ int free_memtype(u64 start, u64 end)
 	int is_range_ram;
 	struct memtype *entry;
 
-	if (!pat_enabled)
+	if (!pat_enabled())
 		return 0;
 
 	/* Low ISA region is always mapped WB. No need to track */
@@ -497,8 +587,8 @@ int free_memtype(u64 start, u64 end)
 	spin_unlock(&memtype_lock);
 
 	if (!entry) {
-		printk(KERN_INFO "%s:%d freeing invalid memtype [mem %#010Lx-%#010Lx]\n",
-		       current->comm, current->pid, start, end - 1);
+		pr_info("x86/PAT: %s:%d freeing invalid memtype [mem %#010Lx-%#010Lx]\n",
+			current->comm, current->pid, start, end - 1);
 		return -EINVAL;
 	}
 
@@ -517,7 +607,7 @@ int free_memtype(u64 start, u64 end)
  * Only to be called when PAT is enabled
  *
  * Returns _PAGE_CACHE_MODE_WB, _PAGE_CACHE_MODE_WC, _PAGE_CACHE_MODE_UC_MINUS
- * or _PAGE_CACHE_MODE_UC
+ * or _PAGE_CACHE_MODE_WT.
  */
 static enum page_cache_mode lookup_memtype(u64 paddr)
 {
@@ -529,16 +619,9 @@ static enum page_cache_mode lookup_memtype(u64 paddr)
 
 	if (pat_pagerange_is_ram(paddr, paddr + PAGE_SIZE)) {
 		struct page *page;
-		page = pfn_to_page(paddr >> PAGE_SHIFT);
-		rettype = get_page_memtype(page);
-		/*
-		 * -1 from get_page_memtype() implies RAM page is in its
-		 * default state and not reserved, and hence of type WB
-		 */
-		if (rettype == -1)
-			rettype = _PAGE_CACHE_MODE_WB;
 
-		return rettype;
+		page = pfn_to_page(paddr >> PAGE_SHIFT);
+		return get_page_memtype(page);
 	}
 
 	spin_lock(&memtype_lock);
@@ -623,13 +706,13 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 	u64 to = from + size;
 	u64 cursor = from;
 
-	if (!pat_enabled)
+	if (!pat_enabled())
 		return 1;
 
 	while (cursor < to) {
 		if (!devmem_is_allowed(pfn)) {
-			printk(KERN_INFO "Program %s tried to access /dev/mem between [mem %#010Lx-%#010Lx], PAT prevents it\n",
-			       current->comm, from, to - 1);
+			pr_info("x86/PAT: Program %s tried to access /dev/mem between [mem %#010Lx-%#010Lx], PAT prevents it\n",
+				current->comm, from, to - 1);
 			return 0;
 		}
 		cursor += PAGE_SIZE;
@@ -659,7 +742,7 @@ 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_enabled &&
+	if (!pat_enabled() &&
 	    !(boot_cpu_has(X86_FEATURE_MTRR) ||
 	      boot_cpu_has(X86_FEATURE_K6_MTRR) ||
 	      boot_cpu_has(X86_FEATURE_CYRIX_ARR) ||
@@ -698,8 +781,7 @@ int kernel_map_sync_memtype(u64 base, unsigned long size,
 				size;
 
 	if (ioremap_change_attr((unsigned long)__va(base), id_sz, pcm) < 0) {
-		printk(KERN_INFO "%s:%d ioremap_change_attr failed %s "
-			"for [mem %#010Lx-%#010Lx]\n",
+		pr_info("x86/PAT: %s:%d ioremap_change_attr failed %s for [mem %#010Lx-%#010Lx]\n",
 			current->comm, current->pid,
 			cattr_name(pcm),
 			base, (unsigned long long)(base + size-1));
@@ -729,12 +811,12 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
 	 * the type requested matches the type of first page in the range.
 	 */
 	if (is_ram) {
-		if (!pat_enabled)
+		if (!pat_enabled())
 			return 0;
 
 		pcm = lookup_memtype(paddr);
 		if (want_pcm != pcm) {
-			printk(KERN_WARNING "%s:%d map pfn RAM range req %s for [mem %#010Lx-%#010Lx], got %s\n",
+			pr_warn("x86/PAT: %s:%d map pfn RAM range req %s for [mem %#010Lx-%#010Lx], got %s\n",
 				current->comm, current->pid,
 				cattr_name(want_pcm),
 				(unsigned long long)paddr,
@@ -755,13 +837,12 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
 		if (strict_prot ||
 		    !is_new_memtype_allowed(paddr, size, want_pcm, pcm)) {
 			free_memtype(paddr, paddr + size);
-			printk(KERN_ERR "%s:%d map pfn expected mapping type %s"
-				" for [mem %#010Lx-%#010Lx], got %s\n",
-				current->comm, current->pid,
-				cattr_name(want_pcm),
-				(unsigned long long)paddr,
-				(unsigned long long)(paddr + size - 1),
-				cattr_name(pcm));
+			pr_err("x86/PAT: %s:%d map pfn expected mapping type %s for [mem %#010Lx-%#010Lx], got %s\n",
+			       current->comm, current->pid,
+			       cattr_name(want_pcm),
+			       (unsigned long long)paddr,
+			       (unsigned long long)(paddr + size - 1),
+			       cattr_name(pcm));
 			return -EINVAL;
 		}
 		/*
@@ -844,7 +925,7 @@ int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 		return ret;
 	}
 
-	if (!pat_enabled)
+	if (!pat_enabled())
 		return 0;
 
 	/*
@@ -872,7 +953,7 @@ int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
 {
 	enum page_cache_mode pcm;
 
-	if (!pat_enabled)
+	if (!pat_enabled())
 		return 0;
 
 	/* Set prot based on lookup */
@@ -913,14 +994,18 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
 
 pgprot_t pgprot_writecombine(pgprot_t prot)
 {
-	if (pat_enabled)
-		return __pgprot(pgprot_val(prot) |
+	return __pgprot(pgprot_val(prot) |
 				cachemode2protval(_PAGE_CACHE_MODE_WC));
-	else
-		return pgprot_noncached(prot);
 }
 EXPORT_SYMBOL_GPL(pgprot_writecombine);
 
+pgprot_t pgprot_writethrough(pgprot_t prot)
+{
+	return __pgprot(pgprot_val(prot) |
+				cachemode2protval(_PAGE_CACHE_MODE_WT));
+}
+EXPORT_SYMBOL_GPL(pgprot_writethrough);
+
 #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
 
 static struct memtype *memtype_get_idx(loff_t pos)
@@ -996,7 +1081,7 @@ static const struct file_operations memtype_fops = {
 
 static int __init pat_memtype_list_init(void)
 {
-	if (pat_enabled) {
+	if (pat_enabled()) {
 		debugfs_create_file("pat_memtype_list", S_IRUSR,
 				    arch_debugfs_dir, NULL, &memtype_fops);
 	}
diff --git a/arch/x86/mm/pat_internal.h b/arch/x86/mm/pat_internal.h
index f641162..a739bfc 100644
--- a/arch/x86/mm/pat_internal.h
+++ b/arch/x86/mm/pat_internal.h
@@ -4,7 +4,7 @@
 extern int pat_debug_enable;
 
 #define dprintk(fmt, arg...) \
-	do { if (pat_debug_enable) printk(KERN_INFO fmt, ##arg); } while (0)
+	do { if (pat_debug_enable) pr_info("x86/PAT: " fmt, ##arg); } while (0)
 
 struct memtype {
 	u64			start;
diff --git a/arch/x86/mm/pat_rbtree.c b/arch/x86/mm/pat_rbtree.c
index 6582adc..6393108 100644
--- a/arch/x86/mm/pat_rbtree.c
+++ b/arch/x86/mm/pat_rbtree.c
@@ -160,9 +160,9 @@ success:
 	return 0;
 
 failure:
-	printk(KERN_INFO "%s:%d conflicting memory types "
-		"%Lx-%Lx %s<->%s\n", current->comm, current->pid, start,
-		end, cattr_name(found_type), cattr_name(match->type));
+	pr_info("x86/PAT: %s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
+		current->comm, current->pid, start, end,
+		cattr_name(found_type), cattr_name(match->type));
 	return -EBUSY;
 }
 
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 0b97d2c..fb0a9dd 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -563,16 +563,31 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
 }
 
 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
+/**
+ * pud_set_huge - setup kernel PUD mapping
+ *
+ * MTRRs can override PAT memory types with 4KiB granularity. Therefore, this
+ * function sets up a huge page only if any of the following conditions are met:
+ *
+ * - MTRRs are disabled, or
+ *
+ * - MTRRs are enabled and the range is completely covered by a single MTRR, or
+ *
+ * - MTRRs are enabled and the corresponding MTRR memory type is WB, which
+ *   has no effect on the requested PAT memory type.
+ *
+ * Callers should try to decrease page size (1GB -> 2MB -> 4K) if the bigger
+ * page mapping attempt fails.
+ *
+ * Returns 1 on success and 0 on failure.
+ */
 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 {
-	u8 mtrr;
+	u8 mtrr, uniform;
 
-	/*
-	 * Do not use a huge page when the range is covered by non-WB type
-	 * of MTRRs.
-	 */
-	mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE);
-	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
+	mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE, &uniform);
+	if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
+	    (mtrr != MTRR_TYPE_WRBACK))
 		return 0;
 
 	prot = pgprot_4k_2_large(prot);
@@ -584,17 +599,24 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 	return 1;
 }
 
+/**
+ * pmd_set_huge - setup kernel PMD mapping
+ *
+ * See text over pud_set_huge() above.
+ *
+ * Returns 1 on success and 0 on failure.
+ */
 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 {
-	u8 mtrr;
+	u8 mtrr, uniform;
 
-	/*
-	 * Do not use a huge page when the range is covered by non-WB type
-	 * of MTRRs.
-	 */
-	mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE);
-	if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != 0xFF))
+	mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE, &uniform);
+	if ((mtrr != MTRR_TYPE_INVALID) && (!uniform) &&
+	    (mtrr != MTRR_TYPE_WRBACK)) {
+		pr_warn_once("%s: Cannot satisfy [mem %#010llx-%#010llx] with a huge-page mapping due to MTRR override.\n",
+			     __func__, addr, addr + PMD_SIZE);
 		return 0;
+	}
 
 	prot = pgprot_4k_2_large(prot);
 
@@ -605,6 +627,11 @@ int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 	return 1;
 }
 
+/**
+ * pud_clear_huge - clear kernel PUD mapping when it is set
+ *
+ * Returns 1 on success and 0 on failure (no PUD map is found).
+ */
 int pud_clear_huge(pud_t *pud)
 {
 	if (pud_large(*pud)) {
@@ -615,6 +642,11 @@ int pud_clear_huge(pud_t *pud)
 	return 0;
 }
 
+/**
+ * pmd_clear_huge - clear kernel PMD mapping when it is set
+ *
+ * Returns 1 on success and 0 on failure (no PMD map is found).
+ */
 int pmd_clear_huge(pmd_t *pmd)
 {
 	if (pmd_large(*pmd)) {