arm64: Use contiguous PTE bit for the kernel linear mapping

index 7d9c7e4..33892ef 100644
@@ -20,14 +20,20 @@
 #define __ASM_PAGE_H
 
 /* PAGE_SHIFT determines the page size */
+/* CONT_SHIFT determines the number of pages which can be tracked together  */
 #ifdef CONFIG_ARM64_64K_PAGES
 #define PAGE_SHIFT		16
+#define CONT_SHIFT		5
 #else
 #define PAGE_SHIFT		12
+#define CONT_SHIFT		4
 #endif
-#define PAGE_SIZE		(_AC(1,UL) << PAGE_SHIFT)
+#define PAGE_SIZE		(_AC(1, UL) << PAGE_SHIFT)
 #define PAGE_MASK		(~(PAGE_SIZE-1))
 
+#define CONT_SIZE		(_AC(1, UL) << (CONT_SHIFT + PAGE_SHIFT))
+#define CONT_MASK		(~(CONT_SIZE-1))
+
 /*
  * The idmap and swapper page tables need some space reserved in the kernel
  * image. Both require pgd, pud (4 levels only) and pmd tables to (section)

index 24154b0..361352d 100644
@@ -55,6 +55,13 @@
 #define SECTION_MASK		(~(SECTION_SIZE-1))
 
 /*
+ * Contiguous page definitions.
+ */
+#define CONT_RANGE		(_AC(1, UL) << CONT_SHIFT)
+#define CONT_RANGE_MASK		((CONT_RANGE-1) << PAGE_SHIFT)
+#define CONT_RANGE_OFFSET(addr) (((addr)>>PAGE_SHIFT)&(CONT_RANGE-1))
+
+/*
  * Hardware page table definitions.
  *
  * Level 1 descriptor (PUD).

@@ -83,6 +90,7 @@
 #define PMD_SECT_S		(_AT(pmdval_t, 3) << 8)
 #define PMD_SECT_AF		(_AT(pmdval_t, 1) << 10)
 #define PMD_SECT_NG		(_AT(pmdval_t, 1) << 11)
+#define PMD_SECT_CONT		(_AT(pmdval_t, 1) << 52)
 #define PMD_SECT_PXN		(_AT(pmdval_t, 1) << 53)
 #define PMD_SECT_UXN		(_AT(pmdval_t, 1) << 54)
 

@@ -105,6 +113,7 @@
 #define PTE_AF			(_AT(pteval_t, 1) << 10)	/* Access Flag */
 #define PTE_NG			(_AT(pteval_t, 1) << 11)	/* nG */
 #define PTE_DBM			(_AT(pteval_t, 1) << 51)	/* Dirty Bit Management */
+#define PTE_CONT		(_AT(pteval_t, 1) << 52)	/* Contiguous range */
 #define PTE_PXN			(_AT(pteval_t, 1) << 53)	/* Privileged XN */
 #define PTE_UXN			(_AT(pteval_t, 1) << 54)	/* User XN */
 

index 6900b2d9..d43e1d1 100644
@@ -144,6 +144,7 @@ extern struct page *empty_zero_page;
 #define pte_special(pte)	(!!(pte_val(pte) & PTE_SPECIAL))
 #define pte_write(pte)		(!!(pte_val(pte) & PTE_WRITE))
 #define pte_exec(pte)		(!(pte_val(pte) & PTE_UXN))
+#define pte_cont(pte)		(!!(pte_val(pte) & PTE_CONT))
 
 #ifdef CONFIG_ARM64_HW_AFDBM
 #define pte_hw_dirty(pte)	(!(pte_val(pte) & PTE_RDONLY))

@@ -206,6 +207,16 @@ static inline pte_t pte_mkspecial(pte_t pte)
 	return set_pte_bit(pte, __pgprot(PTE_SPECIAL));
 }
 
+static inline pte_t pte_mkcont(pte_t pte)
+{
+	return set_pte_bit(pte, __pgprot(PTE_CONT));
+}
+
+static inline pte_t pte_mknoncont(pte_t pte)
+{
+	return clear_pte_bit(pte, __pgprot(PTE_CONT));
+}
+
 static inline void set_pte(pte_t *ptep, pte_t pte)
 {
 	*ptep = pte;

index d43e1d1..252499e 100644
@@ -76,6 +76,8 @@ extern void __pgd_error(const char *file, int line, unsigned long val);
 
 #define PAGE_KERNEL		__pgprot(_PAGE_DEFAULT | PTE_PXN | PTE_UXN | PTE_DIRTY | PTE_WRITE)
 #define PAGE_KERNEL_EXEC	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE)
+#define PAGE_KERNEL_EXEC_CONT	__pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | \
+					 PTE_WRITE | PTE_CONT)
 
 #define PAGE_HYP		__pgprot(_PAGE_DEFAULT | PTE_HYP)
 #define PAGE_HYP_DEVICE		__pgprot(PROT_DEVICE_nGnRE | PTE_HYP)

index f3d6221..5a22a11 100644
@@ -67,6 +67,12 @@ static struct addr_marker address_markers[] = {
 	{ -1,			NULL },
 };
 
+/*
+ * The page dumper groups page table entries of the same type into a single
+ * description. It uses pg_state to track the range information while
+ * iterating over the pte entries. When the continuity is broken it then
+ * dumps out a description of the range.
+ */
 struct pg_state {
 	struct seq_file *seq;
 	const struct addr_marker *marker;

@@ -114,6 +120,16 @@ static const struct prot_bits pte_bits[] = {
 		.set	= "NG",
 		.clear	= "  ",
 	}, {
+		.mask	= PTE_CONT,
+		.val	= PTE_CONT,
+		.set	= "CON",
+		.clear	= "   ",
+	}, {
+		.mask	= PTE_TABLE_BIT,
+		.val	= PTE_TABLE_BIT,
+		.set	= "   ",
+		.clear	= "BLK",
+	}, {
 		.mask	= PTE_UXN,
 		.val	= PTE_UXN,
 		.set	= "UXN",

@@ -198,7 +214,7 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
 		unsigned long delta;
 
 		if (st->current_prot) {
-			seq_printf(st->seq, "0x%16lx-0x%16lx   ",
+			seq_printf(st->seq, "0x%016lx-0x%016lx   ",
 				   st->start_address, addr);
 
 			delta = (addr - st->start_address) >> 10;

index 9211b85..4949f1d 100644
@@ -69,6 +69,8 @@ static void __init *early_alloc(unsigned long sz)
 	return ptr;
 }
 
+early_param_on_off("contpte", "nocontpte", cont_linear_ptes, 1);
+
 /*
  * remap a PMD into pages
  */

@@ -80,19 +82,58 @@ static void split_pmd(pmd_t *pmd, pte_t *pte)
 	do {
 		/*
 		 * Need to have the least restrictive permissions available
-		 * permissions will be fixed up later
+		 * permissions will be fixed up later. Default the new page
+		 * range as contiguous ptes.
 		 */
-		set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
+		if (cont_linear_ptes)
+			set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC_CONT));
+		else
+			set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
 		pfn++;
 	} while (pte++, i++, i < PTRS_PER_PTE);
 }
 
+/*
+ * Given a PTE with the CONT bit set, determine where the CONT range
+ * starts, and clear the entire range of PTE CONT bits.
+ */
+static void clear_cont_pte_range(pte_t *pte, unsigned long addr)
+{
+	int i;
+
+	pte -= CONT_RANGE_OFFSET(addr);
+	for (i = 0; i < CONT_RANGE; i++) {
+		set_pte(pte, pte_mknoncont(*pte));
+		pte++;
+	}
+	flush_tlb_all();
+}
+
+/*
+ * Given a range of PTEs set the pfn and provided page protection flags
+ */
+static void __populate_init_pte(pte_t *pte, unsigned long addr,
+				unsigned long end, phys_addr_t phys,
+				pgprot_t prot)
+{
+	unsigned long pfn = __phys_to_pfn(phys);
+
+	do {
+		/* clear all the bits except the pfn, then apply the prot */
+		set_pte(pte, pfn_pte(pfn, prot));
+		pte++;
+		pfn++;
+		addr += PAGE_SIZE;
+	} while (addr != end);
+}
+
 static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
-				  unsigned long end, unsigned long pfn,
+				  unsigned long end, phys_addr_t phys,
 				  pgprot_t prot,
 				  void *(*alloc)(unsigned long size))
 {
 	pte_t *pte;
+	unsigned long next;
 
 	if (pmd_none(*pmd) || pmd_sect(*pmd)) {
 		pte = alloc(PTRS_PER_PTE * sizeof(pte_t));

@@ -104,10 +145,31 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
 	BUG_ON(pmd_bad(*pmd));
 
 	pte = pte_offset_kernel(pmd, addr);
-	do {
-		set_pte(pte, pfn_pte(pfn, prot));
-		pfn++;
-	} while (pte++, addr += PAGE_SIZE, addr != end);
+	if (!cont_linear_ptes)
+		__populate_init_pte(pte, addr, end, phys, prot);
+	else
+	    do {
+		next = min(end, (addr + CONT_SIZE) & CONT_MASK);
+		if (((addr | next | phys) & CONT_RANGE_MASK) == 0) {
+			/* a block of CONT_RANGE_SIZE PTEs */
+			__populate_init_pte(pte, addr, next, phys,
+					    prot | __pgprot(PTE_CONT));
+		} else {
+			/*
+			 * If the range being split is already inside of a
+			 * contiguous range but this PTE isn't going to be
+			 * contiguous, then we want to unmark the adjacent
+			 * ranges, then update the portion of the range we
+			 * are interrested in.
+			 */
+			 clear_cont_pte_range(pte, addr);
+			 __populate_init_pte(pte, addr, next, phys, prot);
+		}
+
+		pte += (next - addr) >> PAGE_SHIFT;
+		phys += next - addr;
+		addr = next;
+	} while (addr != end);
 }
 
 void split_pud(pud_t *old_pud, pmd_t *pmd)

@@ -168,8 +230,7 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
 				}
 			}
 		} else {
-			alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
-				       prot, alloc);
+			alloc_init_pte(pmd, addr, next, phys, prot, alloc);
 		}
 		phys += next - addr;
 	} while (pmd++, addr = next, addr != end);