ARM: pgtable: switch order of Linux vs hardware page tables

This switches the ordering of the Linux vs hardware page tables in
each page, thereby eliminating some of the arithmetic in the page
table walks.  As we now place the Linux page table at the beginning
of the page, we can deal with the offset in the pgt by simply masking
it away, along with the other control bits.

This also makes the arithmetic all be positive, rather than a mixture.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/pgalloc.h

@@ -35,32 +35,35 @@ extern void pgd_free(struct mm_struct *mm, pgd_t *pgd);
 
 #define PGALLOC_GFP	(GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO)
 
+static inline void clean_pte_table(pte_t *pte)
+{
+	clean_dcache_area(pte + PTE_HWTABLE_PTRS, PTE_HWTABLE_SIZE);
+}
+
 /*
  * Allocate one PTE table.
  *
  * This actually allocates two hardware PTE tables, but we wrap this up
  * into one table thus:
  *
  *  +------------+
- *  |  h/w pt 0  |
- *  +------------+
- *  |  h/w pt 1  |
- *  +------------+
  *  | Linux pt 0 |
  *  +------------+
  *  | Linux pt 1 |
  *  +------------+
+ *  |  h/w pt 0  |
+ *  +------------+
+ *  |  h/w pt 1  |
+ *  +------------+
  */
 static inline pte_t *
 pte_alloc_one_kernel(struct mm_struct *mm, unsigned long addr)
 {
 	pte_t *pte;
 
 	pte = (pte_t *)__get_free_page(PGALLOC_GFP);
-	if (pte) {
-		clean_dcache_area(pte, sizeof(pte_t) * PTRS_PER_PTE);
-		pte += PTRS_PER_PTE;
-	}
+	if (pte)
+		clean_pte_table(pte);
 
 	return pte;
 }
@@ -76,10 +79,8 @@ pte_alloc_one(struct mm_struct *mm, unsigned long addr)
 	pte = alloc_pages(PGALLOC_GFP, 0);
 #endif
 	if (pte) {
-		if (!PageHighMem(pte)) {
-			void *page = page_address(pte);
-			clean_dcache_area(page, sizeof(pte_t) * PTRS_PER_PTE);
-		}
+		if (!PageHighMem(pte))
+			clean_pte_table(page_address(pte));
 		pgtable_page_ctor(pte);
 	}
 
@@ -91,10 +92,8 @@ pte_alloc_one(struct mm_struct *mm, unsigned long addr)
  */
 static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
 {
-	if (pte) {
-		pte -= PTRS_PER_PTE;
+	if (pte)
 		free_page((unsigned long)pte);
-	}
 }
 
 static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
@@ -106,7 +105,7 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
 static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t pte,
 	unsigned long prot)
 {
-	unsigned long pmdval = pte | prot;
+	unsigned long pmdval = (pte + PTE_HWTABLE_OFF) | prot;
 	pmdp[0] = __pmd(pmdval);
 	pmdp[1] = __pmd(pmdval + 256 * sizeof(pte_t));
 	flush_pmd_entry(pmdp);
@@ -121,14 +120,10 @@ static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t pte,
 static inline void
 pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep)
 {
-	unsigned long pte_ptr = (unsigned long)ptep;
-
 	/*
-	 * The pmd must be loaded with the physical
-	 * address of the PTE table
+	 * The pmd must be loaded with the physical address of the PTE table
 	 */
-	pte_ptr -= PTRS_PER_PTE * sizeof(void *);
-	__pmd_populate(pmdp, __pa(pte_ptr), _PAGE_KERNEL_TABLE);
+	__pmd_populate(pmdp, __pa(ptep), _PAGE_KERNEL_TABLE);
 }
 
 static inline void

arch/arm/include/asm/pgtable.h

@@ -55,23 +55,23 @@
  * Therefore, we tweak the implementation slightly - we tell Linux that we
  * have 2048 entries in the first level, each of which is 8 bytes (iow, two
  * hardware pointers to the second level.)  The second level contains two
- * hardware PTE tables arranged contiguously, followed by Linux versions
+ * hardware PTE tables arranged contiguously, preceded by Linux versions
  * which contain the state information Linux needs.  We, therefore, end up
  * with 512 entries in the "PTE" level.
  *
  * This leads to the page tables having the following layout:
  *
  *    pgd             pte
  * |        |
- * +--------+ +0
- * |        |-----> +------------+ +0
+ * +--------+
+ * |        |       +------------+ +0
+ * +- - - - +       | Linux pt 0 |
+ * |        |       +------------+ +1024
+ * +--------+ +0    | Linux pt 1 |
+ * |        |-----> +------------+ +2048
  * +- - - - + +4    |  h/w pt 0  |
- * |        |-----> +------------+ +1024
+ * |        |-----> +------------+ +3072
  * +--------+ +8    |  h/w pt 1  |
- * |        |       +------------+ +2048
- * +- - - - +       | Linux pt 0 |
- * |        |       +------------+ +3072
- * +--------+       | Linux pt 1 |
  * |        |       +------------+ +4096
  *
  * See L_PTE_xxx below for definitions of bits in the "Linux pt", and
@@ -103,6 +103,10 @@
 #define PTRS_PER_PMD		1
 #define PTRS_PER_PGD		2048
 
+#define PTE_HWTABLE_PTRS	(PTRS_PER_PTE)
+#define PTE_HWTABLE_OFF		(PTE_HWTABLE_PTRS * sizeof(pte_t))
+#define PTE_HWTABLE_SIZE	(PTRS_PER_PTE * sizeof(u32))
+
 /*
  * PMD_SHIFT determines the size of the area a second-level page table can map
  * PGDIR_SHIFT determines what a third-level page table entry can map
@@ -323,12 +327,7 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
 
 static inline pte_t *pmd_page_vaddr(pmd_t pmd)
 {
-	phys_addr_t ptr;
-
-	ptr = pmd_val(pmd) & ~(PTRS_PER_PTE * sizeof(void *) - 1);
-	ptr += PTRS_PER_PTE * sizeof(void *);
-
-	return __va(ptr);
+	return __va(pmd_val(pmd) & PAGE_MASK);
 }
 
 #define pmd_page(pmd)		pfn_to_page(__phys_to_pfn(pmd_val(pmd)))
@@ -341,8 +340,8 @@ static inline pte_t *pmd_page_vaddr(pmd_t pmd)
 #define __pte_map(pmd)		pmd_page_vaddr(*(pmd))
 #define __pte_unmap(pte)	do { } while (0)
 #else
-#define __pte_map(pmd)		((pte_t *)kmap_atomic(pmd_page(*(pmd))) + PTRS_PER_PTE)
-#define __pte_unmap(pte)	kunmap_atomic((pte - PTRS_PER_PTE))
+#define __pte_map(pmd)		(pte_t *)kmap_atomic(pmd_page(*(pmd)))
+#define __pte_unmap(pte)	kunmap_atomic(pte)
 #endif
 
 #define pte_index(addr)		(((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))

arch/arm/mm/fault.c

@@ -108,7 +108,7 @@ void show_pte(struct mm_struct *mm, unsigned long addr)
 
 		pte = pte_offset_map(pmd, addr);
 		printk(", *pte=%08lx", pte_val(*pte));
-		printk(", *ppte=%08lx", pte_val(pte[-PTRS_PER_PTE]));
+		printk(", *ppte=%08lx", pte_val(pte[PTE_HWTABLE_PTRS]));
 		pte_unmap(pte);
 	} while(0);
 

arch/arm/mm/proc-macros.S

@@ -121,7 +121,7 @@
 	.endm
 
 	.macro	armv6_set_pte_ext pfx
-	str	r1, [r0], #-2048		@ linux version
+	str	r1, [r0], #2048			@ linux version
 
 	bic	r3, r1, #0x000003fc
 	bic	r3, r3, #PTE_TYPE_MASK
@@ -170,7 +170,7 @@
  *  1111  0xff	r/w	r/w
  */
 	.macro	armv3_set_pte_ext wc_disable=1
-	str	r1, [r0], #-2048		@ linux version
+	str	r1, [r0], #2048			@ linux version
 
 	eor	r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_WRITE | L_PTE_DIRTY
 
@@ -193,7 +193,7 @@
 	bicne	r2, r2, #PTE_BUFFERABLE
 #endif
 	.endif
-	str	r2, [r0]			@ hardware version
+	str	r2, [r0]		@ hardware version
 	.endm
 
 
@@ -213,7 +213,7 @@
  *  1111  11	r/w	r/w
  */
 	.macro	xscale_set_pte_ext_prologue
-	str	r1, [r0], #-2048		@ linux version
+	str	r1, [r0]			@ linux version
 
 	eor	r3, r1, #L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_WRITE | L_PTE_DIRTY
 
@@ -232,7 +232,7 @@
 	tst	r3, #L_PTE_PRESENT | L_PTE_YOUNG	@ present and young?
 	movne	r2, #0				@ no -> fault
 
-	str	r2, [r0]			@ hardware version
+	str	r2, [r0, #2048]!		@ hardware version
 	mov	ip, #0
 	mcr	p15, 0, r0, c7, c10, 1		@ clean L1 D line
 	mcr	p15, 0, ip, c7, c10, 4		@ data write barrier

arch/arm/mm/proc-v7.S

@@ -124,15 +124,13 @@ ENDPROC(cpu_v7_switch_mm)
  *	Set a level 2 translation table entry.
  *
  *	- ptep  - pointer to level 2 translation table entry
- *		  (hardware version is stored at -1024 bytes)
+ *		  (hardware version is stored at +2048 bytes)
  *	- pte   - PTE value to store
  *	- ext	- value for extended PTE bits
  */
 ENTRY(cpu_v7_set_pte_ext)
 #ifdef CONFIG_MMU
- ARM(	str	r1, [r0], #-2048	)	@ linux version
- THUMB(	str	r1, [r0]		)	@ linux version
- THUMB(	sub	r0, r0, #2048		)
+	str	r1, [r0]			@ linux version
 
 	bic	r3, r1, #0x000003f0
 	bic	r3, r3, #PTE_TYPE_MASK
@@ -158,7 +156,7 @@ ENTRY(cpu_v7_set_pte_ext)
 	tstne	r1, #L_PTE_PRESENT
 	moveq	r3, #0
 
-	str	r3, [r0]
+	str	r3, [r0, #2048]!
 	mcr	p15, 0, r0, c7, c10, 1		@ flush_pte
 #endif
 	mov	pc, lr