ARM64: mm: THP support.

Bring Transparent HugePage support to ARM. The size of a
transparent huge page depends on the normal page size. A
transparent huge page is always represented as a pmd.

If PAGE_SIZE is 4KB, THPs are 2MB.
If PAGE_SIZE is 64KB, THPs are 512MB.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -189,6 +189,9 @@ config ARCH_WANT_GENERAL_HUGETLB
 config ARCH_WANT_HUGE_PMD_SHARE
 	def_bool y if !ARM64_64K_PAGES
 
+config HAVE_ARCH_TRANSPARENT_HUGEPAGE
+	def_bool y
+
 source "mm/Kconfig"
 
 config FORCE_MAX_ZONEORDER

arch/arm64/include/asm/pgtable-hwdef.h

@@ -42,6 +42,10 @@
 /*
  * Section
  */
+#define PMD_SECT_VALID		(_AT(pmdval_t, 1) << 0)
+#define PMD_SECT_PROT_NONE	(_AT(pmdval_t, 1) << 2)
+#define PMD_SECT_USER		(_AT(pmdval_t, 1) << 6)		/* AP[1] */
+#define PMD_SECT_RDONLY		(_AT(pmdval_t, 1) << 7)		/* AP[2] */
 #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)

arch/arm64/include/asm/pgtable.h

@@ -187,6 +187,61 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 
 #define __HAVE_ARCH_PTE_SPECIAL
 
+/*
+ * Software PMD bits for THP
+ */
+
+#define PMD_SECT_DIRTY		(_AT(pmdval_t, 1) << 55)
+#define PMD_SECT_SPLITTING	(_AT(pmdval_t, 1) << 57)
+
+/*
+ * THP definitions.
+ */
+#define pmd_young(pmd)		(pmd_val(pmd) & PMD_SECT_AF)
+
+#define __HAVE_ARCH_PMD_WRITE
+#define pmd_write(pmd)		(!(pmd_val(pmd) & PMD_SECT_RDONLY))
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#define pmd_trans_huge(pmd)	(pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
+#define pmd_trans_splitting(pmd) (pmd_val(pmd) & PMD_SECT_SPLITTING)
+#endif
+
+#define PMD_BIT_FUNC(fn,op) \
+static inline pmd_t pmd_##fn(pmd_t pmd) { pmd_val(pmd) op; return pmd; }
+
+PMD_BIT_FUNC(wrprotect,	|= PMD_SECT_RDONLY);
+PMD_BIT_FUNC(mkold,	&= ~PMD_SECT_AF);
+PMD_BIT_FUNC(mksplitting, |= PMD_SECT_SPLITTING);
+PMD_BIT_FUNC(mkwrite,   &= ~PMD_SECT_RDONLY);
+PMD_BIT_FUNC(mkdirty,   |= PMD_SECT_DIRTY);
+PMD_BIT_FUNC(mkyoung,   |= PMD_SECT_AF);
+PMD_BIT_FUNC(mknotpresent, &= ~PMD_TYPE_MASK);
+
+#define pmd_mkhuge(pmd)		(__pmd(pmd_val(pmd) & ~PMD_TABLE_BIT))
+
+#define pmd_pfn(pmd)		(((pmd_val(pmd) & PMD_MASK) & PHYS_MASK) >> PAGE_SHIFT)
+#define pfn_pmd(pfn,prot)	(__pmd(((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot)))
+#define mk_pmd(page,prot)	pfn_pmd(page_to_pfn(page),prot)
+
+#define pmd_page(pmd)           pfn_to_page(__phys_to_pfn(pmd_val(pmd) & PHYS_MASK))
+
+static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
+{
+	const pmdval_t mask = PMD_SECT_USER | PMD_SECT_PXN | PMD_SECT_UXN |
+			      PMD_SECT_RDONLY | PMD_SECT_PROT_NONE |
+			      PMD_SECT_VALID;
+	pmd_val(pmd) = (pmd_val(pmd) & ~mask) | (pgprot_val(newprot) & mask);
+	return pmd;
+}
+
+#define set_pmd_at(mm, addr, pmdp, pmd)	set_pmd(pmdp, pmd)
+
+static inline int has_transparent_hugepage(void)
+{
+	return 1;
+}
+
 /*
  * Mark the prot value as uncacheable and unbufferable.
  */

arch/arm64/include/asm/tlb.h

@@ -187,4 +187,10 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp,
 
 #define tlb_migrate_finish(mm)		do { } while (0)
 
+static inline void
+tlb_remove_pmd_tlb_entry(struct mmu_gather *tlb, pmd_t *pmdp, unsigned long addr)
+{
+	tlb_add_flush(tlb, addr);
+}
+
 #endif

arch/arm64/include/asm/tlbflush.h

@@ -117,6 +117,8 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
 	dsb();
 }
 
+#define update_mmu_cache_pmd(vma, address, pmd) do { } while (0)
+
 #endif
 
 #endif