powerpc/mm/hugetlb: add support for 1G huge pages

POWER9 supports hugepages of size 2M and 1G in radix MMU mode.  This
patch enables the usage of 1G page size for hugetlbfs.  This also update
the helper such we can do 1G page allocation at runtime.

We still don't enable 1G page size on DD1 version.  This is to avoid
doing workaround mentioned in commit 6d3a0379eb ("powerpc/mm: Add
radix__tlb_flush_pte_p9_dd1()").

Link: http://lkml.kernel.org/r/1494995292-4443-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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

@@ -50,4 +50,14 @@ static inline pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
 	else
 		return entry;
 }
+
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
+static inline bool gigantic_page_supported(void)
+{
+	if (radix_enabled())
+		return true;
+	return false;
+}
+#endif
+
 #endif

arch/powerpc/mm/hugetlbpage.c

@@ -742,8 +742,11 @@ static int __init add_huge_page_size(unsigned long long size)
 	 * Hash: 16M and 16G
 	 */
 	if (radix_enabled()) {
-		if (mmu_psize != MMU_PAGE_2M)
-			return -EINVAL;
+		if (mmu_psize != MMU_PAGE_2M) {
+			if (cpu_has_feature(CPU_FTR_POWER9_DD1) ||
+			    (mmu_psize != MMU_PAGE_1G))
+				return -EINVAL;
+		}
 	} else {
 		if (mmu_psize != MMU_PAGE_16M && mmu_psize != MMU_PAGE_16G)
 			return -EINVAL;

arch/powerpc/platforms/Kconfig.cputype

@@ -344,6 +344,7 @@ config PPC_STD_MMU_64
 config PPC_RADIX_MMU
 	bool "Radix MMU Support"
 	depends on PPC_BOOK3S_64
+	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
 	default y
 	help
 	  Enable support for the Power ISA 3.0 Radix style MMU. Currently this