riscv: Implement missing huge_ptep_get

huge_ptep_get must be reimplemented in order to go through all the PTEs
of a NAPOT region: this is needed because the HW can update the A/D bits
of any of the PTE that constitutes the NAPOT region.

Fixes: 82a1a1f ("riscv: mm: support Svnapot in hugetlb page")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20230428120120.21620-2-alexghiti@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Alexandre Ghiti

arch/riscv/include/asm/hugetlb.h

@@ -36,6 +36,9 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma,
 			       unsigned long addr, pte_t *ptep,
 			       pte_t pte, int dirty);
 
+#define __HAVE_ARCH_HUGE_PTEP_GET
+pte_t huge_ptep_get(pte_t *ptep);
+
 pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags);
 #define arch_make_huge_pte arch_make_huge_pte
 

arch/riscv/mm/hugetlbpage.c

@@ -3,6 +3,30 @@
 #include <linux/err.h>
 
 #ifdef CONFIG_RISCV_ISA_SVNAPOT
+pte_t huge_ptep_get(pte_t *ptep)
+{
+	unsigned long pte_num;
+	int i;
+	pte_t orig_pte = ptep_get(ptep);
+
+	if (!pte_present(orig_pte) || !pte_napot(orig_pte))
+		return orig_pte;
+
+	pte_num = napot_pte_num(napot_cont_order(orig_pte));
+
+	for (i = 0; i < pte_num; i++, ptep++) {
+		pte_t pte = ptep_get(ptep);
+
+		if (pte_dirty(pte))
+			orig_pte = pte_mkdirty(orig_pte);
+
+		if (pte_young(pte))
+			orig_pte = pte_mkyoung(orig_pte);
+	}
+
+	return orig_pte;
+}
+
 pte_t *huge_pte_alloc(struct mm_struct *mm,
 		      struct vm_area_struct *vma,
 		      unsigned long addr,