thp: don't allow transparent hugepage support without PSE

Archs implementing Transparent Hugepage Support must implement a function
called has_transparent_hugepage to be sure the virtual or physical CPU
supports Transparent Hugepages.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index c48ba055f693..18601c86fab1 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -160,6 +160,11 @@ static inline int pmd_trans_huge(pmd_t pmd)
 {
         return pmd_val(pmd) & _PAGE_PSE;
 }
+
+static inline int has_transparent_hugepage(void)
+{
+        return cpu_has_pse;
+}
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 static inline pte_t pte_set_flags(pte_t pte, pteval_t set)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b6facc35e893..915809b16edf 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -487,7 +487,15 @@ static int __init hugepage_init(void)
         int err;
 #ifdef CONFIG_SYSFS
         static struct kobject *hugepage_kobj;
+#endif
 
+        err = -EINVAL;
+        if (!has_transparent_hugepage()) {
+                transparent_hugepage_flags = 0;
+                goto out;
+        }
+
+#ifdef CONFIG_SYSFS
         err = -ENOMEM;
         hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
         if (unlikely(!hugepage_kobj)) {