[PATCH RFC v3 11/21] riscv: mm: use proper set_pXd() for generic compile-time folded patable in vmalloc_fault()

[Yeoreum Yun <yeoreum.yun@arm.com>]

The behaviour of pXdp_get() will change with generic compile-time folded
page tables, making it invalid to use set_pXd() with the result of
pXdp_get(). Instead, the appropriate first-level set_pXd() must be paired
with the corresponding pXdp_get().

Therefore, call the appropriate set_pXd() for generic compile-time folded
page tables so that vmalloc_fault() continues to handle folded entries
correctly when checking pXd_present().

There should be no functional change.

Since most architectures use a similar pattern to handle vmalloc fault
by syncing the faulted entry, it would be worth cleaning this up by
introducing a common helper in the near future.

Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 arch/riscv/mm/fault.c | 52 ++++++++++++++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 19 deletions(-)

diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 04ed6f8acae4..b2bcaf10d13f 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -167,14 +167,16 @@ bad_area(struct pt_regs *regs, struct mm_struct *mm, int code,
 
 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
 {
-	pgd_t *pgd, *pgd_k;
-	pud_t *pud_k;
-	p4d_t *p4d_k;
-	pmd_t *pmd_k;
-	pte_t *pte_k;
+	pgd_t *pgdp_k, *pgdp, pgd_k;
+	p4d_t *p4dp_k, *p4dp;
+	pud_t *pudp_k, *pudp, pud_k;
+	pmd_t *pmdp_k, *pmdp, pmd_k;
+	pte_t *ptep_k;
 	int index;
 	unsigned long pfn;
 
+	BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS != 5 && CONFIG_PGTABLE_LEVELS != 2);
+
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs))
 		return do_trap(regs, SIGSEGV, code, addr);
@@ -189,39 +191,51 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
 	 */
 	index = pgd_index(addr);
 	pfn = csr_read(CSR_SATP) & SATP_PPN;
-	pgd = (pgd_t *)pfn_to_virt(pfn) + index;
-	pgd_k = init_mm.pgd + index;
 
-	if (!pgd_present(pgdp_get(pgd_k))) {
+	pgdp = (pgd_t *)pfn_to_virt(pfn) + index;
+	pgdp_k = init_mm.pgd + index;
+
+	pgd_k = pgdp_get(pgdp_k);
+	if (!pgd_present(pgd_k)) {
 		no_context(regs, addr);
 		return;
 	}
-	set_pgd(pgd, pgdp_get(pgd_k));
+	if (CONFIG_PGTABLE_LEVELS == 5)
+		set_pgd(pgdp, pgd_k);
 
-	p4d_k = p4d_offset(pgd_k, addr);
-	if (!p4d_present(p4dp_get(p4d_k))) {
+	p4dp = p4d_offset(pgdp, addr);
+	p4dp_k = p4d_offset(pgdp_k, addr);
+	if (!p4d_present(p4dp_get(p4dp_k))) {
 		no_context(regs, addr);
 		return;
 	}
 
-	pud_k = pud_offset(p4d_k, addr);
-	if (!pud_present(pudp_get(pud_k))) {
+	pudp = pud_offset(p4dp, addr);
+	pudp_k = pud_offset(p4dp_k, addr);
+
+	pud_k = pudp_get(pudp_k);
+	if (!pud_present(pud_k)) {
 		no_context(regs, addr);
 		return;
 	}
-	if (pud_leaf(pudp_get(pud_k)))
+	if (pud_leaf(pud_k))
 		goto flush_tlb;
 
 	/*
 	 * Since the vmalloc area is global, it is unnecessary
 	 * to copy individual PTEs
 	 */
-	pmd_k = pmd_offset(pud_k, addr);
-	if (!pmd_present(pmdp_get(pmd_k))) {
+	pmdp = pmd_offset(pudp, addr);
+	pmdp_k = pmd_offset(pudp_k, addr);
+
+	pmd_k = pmdp_get(pmdp_k);
+	if (!pmd_present(pmd_k)) {
 		no_context(regs, addr);
 		return;
 	}
-	if (pmd_leaf(pmdp_get(pmd_k)))
+	if (CONFIG_PGTABLE_LEVELS == 2)
+		set_pmd(pmdp, pmd_k);
+	if (pmd_leaf(pmd_k))
 		goto flush_tlb;
 
 	/*
@@ -230,8 +244,8 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
 	 * addresses. If we don't do this, this will just
 	 * silently loop forever.
 	 */
-	pte_k = pte_offset_kernel(pmd_k, addr);
-	if (!pte_present(ptep_get(pte_k))) {
+	ptep_k = pte_offset_kernel(pmdp_k, addr);
+	if (!pte_present(ptep_get(ptep_k))) {
 		no_context(regs, addr);
 		return;
 	}

-- 
2.43.0