linux-kernel - [PATCH] parisc: map_pages(): cleanup page table initialization

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Message-Id: <20200112113615.24198-1-rppt@kernel.org>
Date:   Sun, 12 Jan 2020 13:36:15 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Helge Deller <deller@....de>
Cc:     "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Meelis Roos <mroos@...ux.ee>, Jeroen Roovers <jer@...too.org>,
        Mikulas Patocka <mpatocka@...hat.com>,
        linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: [PATCH] parisc: map_pages(): cleanup page table initialization

From: Mike Rapoport <rppt@...ux.ibm.com>

The current code uses '#if PTRS_PER_PMD == 1' to distinguish 2 vs 3 levels,
setup, it casts pgd to pgd to cope with page table folding and converts
addresses of page table entries from physical to virtual and back for no
good reason.

Simplify the accesses to the page table entries using proper unfolding of
the upper layers and replacing '#if PTRS_PER_PMD' with explicit
'#if CONFIG_PGTABLE_LEVELS == 3'

Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
---
Hi,

This patch is on top of the current parisc/for-next.
I've build-tested for generic-{32,64}_defconfig and was able to boot
qemu-system-parisc up to rootfs mount.

 arch/parisc/mm/init.c | 50 +++++++++++--------------------------------
 1 file changed, 12 insertions(+), 38 deletions(-)

diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index 354cf060b67f..5224fb38d766 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -351,7 +351,6 @@ static void __init map_pages(unsigned long start_vaddr,
 			     unsigned long start_paddr, unsigned long size,
 			     pgprot_t pgprot, int force)
 {
-	pgd_t *pg_dir;
 	pmd_t *pmd;
 	pte_t *pg_table;
 	unsigned long end_paddr;
@@ -372,62 +371,37 @@ static void __init map_pages(unsigned long start_vaddr,
 
 	end_paddr = start_paddr + size;
 
-	pg_dir = pgd_offset_k(start_vaddr);
-
-#if PTRS_PER_PMD == 1
-	start_pmd = 0;
-#else
+	/* for 2-level configuration PTRS_PER_PMD is 0 so start_pmd will be 0 */
 	start_pmd = ((start_vaddr >> PMD_SHIFT) & (PTRS_PER_PMD - 1));
-#endif
 	start_pte = ((start_vaddr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1));
 
 	address = start_paddr;
 	vaddr = start_vaddr;
 	while (address < end_paddr) {
-#if PTRS_PER_PMD == 1
-		pmd = (pmd_t *)__pa(pg_dir);
-#else
-		pmd = (pmd_t *)pgd_address(*pg_dir);
-
-		/*
-		 * pmd is physical at this point
-		 */
+		pgd_t *pgd = pgd_offset_k(vaddr);
+		p4d_t *p4d = p4d_offset(pgd, vaddr);
+		pud_t *pud = pud_offset(p4d, vaddr);
 
-		if (!pmd) {
+#if CONFIG_PGTABLE_LEVELS == 3
+		if (pud_none(*pud)) {
 			pmd = memblock_alloc(PAGE_SIZE << PMD_ORDER,
 					     PAGE_SIZE << PMD_ORDER);
 			if (!pmd)
 				panic("pmd allocation failed.\n");
-			pmd = (pmd_t *) __pa(pmd);
+			pud_populate(NULL, pud, pmd);
 		}
-
-		pud_populate(NULL, (pud_t *)pg_dir, __va(pmd));
 #endif
-		pg_dir++;
-
-		/* now change pmd to kernel virtual addresses */
 
-		pmd = (pmd_t *)__va(pmd) + start_pmd;
+		pmd = pmd_offset(pud, vaddr);
 		for (tmp1 = start_pmd; tmp1 < PTRS_PER_PMD; tmp1++, pmd++) {
-
-			/*
-			 * pg_table is physical at this point
-			 */
-
-			pg_table = (pte_t *)pmd_address(*pmd);
-			if (!pg_table) {
-				pg_table = memblock_alloc(PAGE_SIZE,
-							  PAGE_SIZE);
+			if (pmd_none(*pmd)) {
+				pg_table = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
 				if (!pg_table)
 					panic("page table allocation failed\n");
-				pg_table = (pte_t *) __pa(pg_table);
+				pmd_populate_kernel(NULL, pmd, pg_table);
 			}
 
-			pmd_populate_kernel(NULL, pmd, __va(pg_table));
-
-			/* now change pg_table to kernel virtual addresses */
-
-			pg_table = (pte_t *) __va(pg_table) + start_pte;
+			pg_table = pte_offset_kernel(pmd, vaddr);
 			for (tmp2 = start_pte; tmp2 < PTRS_PER_PTE; tmp2++, pg_table++) {
 				pte_t pte;
 				pgprot_t prot;

base-commit: 9cf86a639ffdd9c38d510d35efcc15ed6dfb2efa
-- 
2.24.0