Currently, this is always true if the VMA is shared. In the future, it's
possible that private mappings will get some or all HGM functionality.

Signed-off-by: James Houghton <jthoughton@google.com>
---
 include/linux/hugetlb.h | 10 ++++++++++
 mm/hugetlb.c            |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 33ba48fac551..e7a6b944d0cc 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1174,6 +1174,16 @@ static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 }
 #endif	/* CONFIG_HUGETLB_PAGE */
 
+#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
+/* If HugeTLB high-granularity mappings are enabled for this VMA. */
+bool hugetlb_hgm_enabled(struct vm_area_struct *vma);
+#else
+static inline bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
+{
+	return false;
+}
+#endif
+
 static inline spinlock_t *huge_pte_lock(struct hstate *h,
 					struct mm_struct *mm, pte_t *pte)
 {
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a2d2ffa76173..8b10b941458d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6983,6 +6983,14 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
 
 #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
 
+#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
+bool hugetlb_hgm_enabled(struct vm_area_struct *vma)
+{
+	/* All shared VMAs have HGM enabled. */
+	return vma->vm_flags & VM_SHARED;
+}
+#endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
+
 /*
  * These functions are overwritable if your architecture needs its own
  * behavior.
