LoongArch: mm: Introduce unified function populate_kernel_pte()

Function pcpu_populate_pte() and fixmap_pte() are similar, they populate
one page from kernel address space. And there is confusion between pgd
and p4d in the function fixmap_pte(), such as pgd_none() always returns
zero. This patch introduces a unified function populate_kernel_pte() and
then replaces pcpu_populate_pte() and fixmap_pte().

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: bibo-mao

arch/loongarch/include/asm/pgalloc.h

@@ -91,4 +91,5 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
 
 #endif /* __PAGETABLE_PUD_FOLDED */
 
+extern pte_t * __init populate_kernel_pte(unsigned long addr);
 #endif /* _ASM_PGALLOC_H */

arch/loongarch/kernel/numa.c

@@ -67,41 +67,7 @@ static int __init pcpu_cpu_distance(unsigned int from, unsigned int to)
 
 void __init pcpu_populate_pte(unsigned long addr)
 {
-	pgd_t *pgd = pgd_offset_k(addr);
-	p4d_t *p4d = p4d_offset(pgd, addr);
-	pud_t *pud;
-	pmd_t *pmd;
-
-	if (p4d_none(*p4d)) {
-		pud = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
-		if (!pud)
-			panic("%s: Failed to allocate memory\n", __func__);
-		p4d_populate(&init_mm, p4d, pud);
-#ifndef __PAGETABLE_PUD_FOLDED
-		pud_init(pud);
-#endif
-	}
-
-	pud = pud_offset(p4d, addr);
-	if (pud_none(*pud)) {
-		pmd = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
-		if (!pmd)
-			panic("%s: Failed to allocate memory\n", __func__);
-		pud_populate(&init_mm, pud, pmd);
-#ifndef __PAGETABLE_PMD_FOLDED
-		pmd_init(pmd);
-#endif
-	}
-
-	pmd = pmd_offset(pud, addr);
-	if (!pmd_present(*pmd)) {
-		pte_t *pte;
-
-		pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
-		if (!pte)
-			panic("%s: Failed to allocate memory\n", __func__);
-		pmd_populate_kernel(&init_mm, pmd, pte);
-	}
+	populate_kernel_pte(addr);
 }
 
 void __init setup_per_cpu_areas(void)

arch/loongarch/mm/init.c

@@ -191,43 +191,42 @@ void vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *al
 #endif
 #endif
 
-static pte_t *fixmap_pte(unsigned long addr)
+pte_t * __init populate_kernel_pte(unsigned long addr)
 {
-	pgd_t *pgd;
-	p4d_t *p4d;
+	pgd_t *pgd = pgd_offset_k(addr);
+	p4d_t *p4d = p4d_offset(pgd, addr);
 	pud_t *pud;
 	pmd_t *pmd;
 
-	pgd = pgd_offset_k(addr);
-	p4d = p4d_offset(pgd, addr);
-
-	if (pgd_none(*pgd)) {
-		pud_t *new __maybe_unused;
-
-		new = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
-		pgd_populate(&init_mm, pgd, new);
+	if (p4d_none(*p4d)) {
+		pud = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
+		if (!pud)
+			panic("%s: Failed to allocate memory\n", __func__);
+		p4d_populate(&init_mm, p4d, pud);
 #ifndef __PAGETABLE_PUD_FOLDED
-		pud_init(new);
+		pud_init(pud);
 #endif
 	}
 
 	pud = pud_offset(p4d, addr);
 	if (pud_none(*pud)) {
-		pmd_t *new __maybe_unused;
-
-		new = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
-		pud_populate(&init_mm, pud, new);
+		pmd = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
+		if (!pmd)
+			panic("%s: Failed to allocate memory\n", __func__);
+		pud_populate(&init_mm, pud, pmd);
 #ifndef __PAGETABLE_PMD_FOLDED
-		pmd_init(new);
+		pmd_init(pmd);
 #endif
 	}
 
 	pmd = pmd_offset(pud, addr);
-	if (pmd_none(*pmd)) {
-		pte_t *new __maybe_unused;
+	if (!pmd_present(*pmd)) {
+		pte_t *pte;
 
-		new = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
-		pmd_populate_kernel(&init_mm, pmd, new);
+		pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
+		if (!pte)
+			panic("%s: Failed to allocate memory\n", __func__);
+		pmd_populate_kernel(&init_mm, pmd, pte);
 	}
 
 	return pte_offset_kernel(pmd, addr);
@@ -241,7 +240,7 @@ void __init __set_fixmap(enum fixed_addresses idx,
 
 	BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
 
-	ptep = fixmap_pte(addr);
+	ptep = populate_kernel_pte(addr);
 	if (!pte_none(*ptep)) {
 		pte_ERROR(*ptep);
 		return;