powerpc/mm: Introduce _PAGE_LARGE software pte bits

This patch adds a new software defined pte bit. We use the reserved
fields of ISA 3.0 pte definition since we will only be using this on DD1
code paths. We can possibly look at removing this code later.

The software bit will be used to differentiate between 64K/4K and 2M
ptes. This helps in finding the page size mapping by a pte so that we
can do efficient tlb flush.

We don't support 1G hugetlb pages yet. So we add a DEBUG WARN_ON to
catch wrong usage.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/hugetlb.h

@@ -30,4 +30,24 @@ static inline int hstate_get_psize(struct hstate *hstate)
 		return mmu_virtual_psize;
 	}
 }
+
+#define arch_make_huge_pte arch_make_huge_pte
+static inline pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
+				       struct page *page, int writable)
+{
+	unsigned long page_shift;
+
+	if (!cpu_has_feature(CPU_FTR_POWER9_DD1))
+		return entry;
+
+	page_shift = huge_page_shift(hstate_vma(vma));
+	/*
+	 * We don't support 1G hugetlb pages yet.
+	 */
+	VM_WARN_ON(page_shift == mmu_psize_defs[MMU_PAGE_1G].shift);
+	if (page_shift == mmu_psize_defs[MMU_PAGE_2M].shift)
+		return __pte(pte_val(entry) | _PAGE_LARGE);
+	else
+		return entry;
+}
 #endif

arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -26,6 +26,11 @@
 #define _RPAGE_SW1		0x00800
 #define _RPAGE_SW2		0x00400
 #define _RPAGE_SW3		0x00200
+#define _RPAGE_RSV1		0x1000000000000000UL
+#define _RPAGE_RSV2		0x0800000000000000UL
+#define _RPAGE_RSV3		0x0400000000000000UL
+#define _RPAGE_RSV4		0x0200000000000000UL
+
 #ifdef CONFIG_MEM_SOFT_DIRTY
 #define _PAGE_SOFT_DIRTY	_RPAGE_SW3 /* software: software dirty tracking */
 #else
@@ -33,6 +38,11 @@
 #endif
 #define _PAGE_SPECIAL		_RPAGE_SW2 /* software: special page */
 
+/*
+ * For P9 DD1 only, we need to track whether the pte's huge.
+ */
+#define _PAGE_LARGE	_RPAGE_RSV1
+
 
 #define _PAGE_PTE		(1ul << 62)	/* distinguishes PTEs from pointers */
 #define _PAGE_PRESENT		(1ul << 63)	/* pte contains a translation */

arch/powerpc/include/asm/book3s/64/radix.h

@@ -243,6 +243,8 @@ static inline int radix__pmd_trans_huge(pmd_t pmd)
 
 static inline pmd_t radix__pmd_mkhuge(pmd_t pmd)
 {
+	if (cpu_has_feature(CPU_FTR_POWER9_DD1))
+		return __pmd(pmd_val(pmd) | _PAGE_PTE | _PAGE_LARGE);
 	return __pmd(pmd_val(pmd) | _PAGE_PTE);
 }
 static inline void radix__pmdp_huge_split_prepare(struct vm_area_struct *vma,