riscv: mm: Remove the copy operation of pmd

Since all processes share the kernel address space,
we only need to copy pgd in case of a vmalloc page
fault exception, the other levels of page tables are
shared, so the operation of copying pmd is unnecessary.
Signed-off-by: Chuanhua Han <hanchuanhua@oppo.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/mm/fault.c

@@ -102,9 +102,9 @@ static inline void 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, *pud_k;
-	p4d_t *p4d, *p4d_k;
-	pmd_t *pmd, *pmd_k;
+	pud_t *pud_k;
+	p4d_t *p4d_k;
+	pmd_t *pmd_k;
 	pte_t *pte_k;
 	int index;
 	unsigned long pfn;
@@ -132,14 +132,12 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
 	}
 	set_pgd(pgd, *pgd_k);
 
-	p4d = p4d_offset(pgd, addr);
 	p4d_k = p4d_offset(pgd_k, addr);
 	if (!p4d_present(*p4d_k)) {
 		no_context(regs, addr);
 		return;
 	}
 
-	pud = pud_offset(p4d, addr);
 	pud_k = pud_offset(p4d_k, addr);
 	if (!pud_present(*pud_k)) {
 		no_context(regs, addr);
@@ -150,13 +148,11 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
 	 * Since the vmalloc area is global, it is unnecessary
 	 * to copy individual PTEs
 	 */
-	pmd = pmd_offset(pud, addr);
 	pmd_k = pmd_offset(pud_k, addr);
 	if (!pmd_present(*pmd_k)) {
 		no_context(regs, addr);
 		return;
 	}
-	set_pmd(pmd, *pmd_k);
 
 	/*
 	 * Make sure the actual PTE exists as well to