[PATCH -fixes 2/2] riscv: Fix set_huge_pte_at() for NAPOT mappings when a swap entry is set

[Alexandre Ghiti]

We used to determine the number of page table entries to set for a NAPOT
hugepage by using the pte value which actually fails when the pte to set is
a swap entry.

So take advantage of a recent fix for arm64 reported in [1] which
introduces the size of the mapping as an argument of set_huge_pte_at(): we
can then use this size to compute the number of page table entries to set
for a NAPOT region.

Fixes: 82a1a1f3bfb6 ("riscv: mm: support Svnapot in hugetlb page")
Reported-by: Ryan Roberts <ryan.roberts at arm.com>
Closes: https://lore.kernel.org/linux-arm-kernel/20230922115804.2043771-1-ryan.roberts@arm.com/ [1]
Signed-off-by: Alexandre Ghiti <alexghiti at rivosinc.com>
---
 arch/riscv/mm/hugetlbpage.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
index e4a2ace92dbe..b52f0210481f 100644
--- a/arch/riscv/mm/hugetlbpage.c
+++ b/arch/riscv/mm/hugetlbpage.c
@@ -183,15 +183,22 @@ void set_huge_pte_at(struct mm_struct *mm,
 		     pte_t pte,
 		     unsigned long sz)
 {
+	unsigned long hugepage_shift;
 	int i, pte_num;
 
-	if (!pte_napot(pte)) {
-		set_pte_at(mm, addr, ptep, pte);
-		return;
-	}
+	if (sz >= PGDIR_SIZE)
+		hugepage_shift = PGDIR_SHIFT;
+	else if (sz >= P4D_SIZE)
+		hugepage_shift = P4D_SHIFT;
+	else if (sz >= PUD_SIZE)
+		hugepage_shift = PUD_SHIFT;
+	else if (sz >= PMD_SIZE)
+		hugepage_shift = PMD_SHIFT;
+	else
+		hugepage_shift = PAGE_SHIFT;
 
-	pte_num = napot_pte_num(napot_cont_order(pte));
-	for (i = 0; i < pte_num; i++, ptep++, addr += PAGE_SIZE)
+	pte_num = sz >> hugepage_shift;
+	for (i = 0; i < pte_num; i++, ptep++, addr += (1 << hugepage_shift))
 		set_pte_at(mm, addr, ptep, pte);
 }
 
-- 
2.39.2