[RFC PATCH] powerpc/mm/hugetlb: Add support for 1G huge pages

[Aneesh Kumar K.V]

This patch adds support for gigantic pages in ppc64. We also updates
gigantic_page_supported helper such that arch can override it.

Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/hugetlb.h | 9 +++++++++
 arch/powerpc/mm/hugetlbpage.c                | 7 +++++--
 arch/powerpc/platforms/Kconfig.cputype       | 1 +
 mm/hugetlb.c                                 | 4 ++++
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hugetlb.h 
b/arch/powerpc/include/asm/book3s/64/hugetlb.h
index 6666cd366596..a994d069fdaf 100644
--- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
+++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
@@ -50,4 +50,13 @@ static inline pte_t arch_make_huge_pte(pte_t entry, struct 
vm_area_struct *vma,
        else
                return entry;
 }
+
+#define gigantic_page_supported gigantic_page_supported
+static inline bool gigantic_page_supported(void)
+{
+       if (radix_enabled())
+               return true;
+       return false;
+}
+
 #endif
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index a4f33de4008e..80f6d2ed551a 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -763,8 +763,11 @@ 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;
diff --git a/arch/powerpc/platforms/Kconfig.cputype 
b/arch/powerpc/platforms/Kconfig.cputype
index a7c0c1fafe68..382c3dd86d6d 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -343,6 +343,7 @@ config PPC_STD_MMU_64
 config PPC_RADIX_MMU
        bool "Radix MMU Support"
        depends on PPC_BOOK3S_64
+       select ARCH_HAS_GIGANTIC_PAGE
        default y
        help
          Enable support for the Power ISA 3.0 Radix style MMU. Currently this
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3d0aab9ee80d..2c090189f314 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1158,7 +1158,11 @@ static int alloc_fresh_gigantic_page(struct hstate *h,
        return 0;
 }
 
+#ifndef gigantic_page_supported
 static inline bool gigantic_page_supported(void) { return true; }
+#define gigantic_page_supported gigantic_page_supported
+#endif
+
 #else
 static inline bool gigantic_page_supported(void) { return false; }
 static inline void free_gigantic_page(struct page *page, unsigned int order) { 
}
-- 
2.7.4