arm64: hugetlb: set_huge_pte_at Add WARN_ON on !pte_present

This patch adds a WARN_ON to set_huge_pte_at as the accessor assumes
that entries to be written down are all present. (There are separate
accessors to clear huge ptes).

We will need to handle the !pte_present case where memory offlining
is used on hugetlb pages. swap and migration entries will be supplied
to set_huge_pte_at in this case.

Cc: David Woods <dwoods@mellanox.com>
Signed-off-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 656e0ece2289..7b61e4833432 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -67,6 +67,12 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
         unsigned long pfn;
         pgprot_t hugeprot;
 
+        /*
+         * Code needs to be expanded to handle huge swap and migration
+         * entries. Needed for HUGETLB and MEMORY_FAILURE.
+         */
+        WARN_ON(!pte_present(pte));
+
         if (!pte_cont(pte)) {
                 set_pte_at(mm, addr, ptep, pte);
                 return;