linux-kernel - [PATCH AUTOSEL 6.0 25/39] LoongArch: Set _PAGE_DIRTY only if _PAGE_MODIFIED is set in {pmd,pte}

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Date:   Mon, 28 Nov 2022 12:36:05 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Huacai Chen <chenhuacai@...ngson.cn>, Guo Ren <guoren@...nel.org>,
        Sasha Levin <sashal@...nel.org>, chenhuacai@...nel.org,
        akpm@...ux-foundation.org, rppt@...nel.org,
        jiaxun.yang@...goat.com, git@...0n.name, loongarch@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.0 25/39] LoongArch: Set _PAGE_DIRTY only if _PAGE_MODIFIED is set in {pmd,pte}_mkwrite()

From: Huacai Chen <chenhuacai@...ngson.cn>

[ Upstream commit 54e6cd42a183b602e3627ad3aaeeed44f7443e67 ]

Set _PAGE_DIRTY only if _PAGE_MODIFIED is set in {pmd,pte}_mkwrite().
Otherwise, _PAGE_DIRTY silences the TLB modify exception and make us
have no chance to mark a pmd/pte dirty (_PAGE_MODIFIED) for software.

Reviewed-by: Guo Ren <guoren@...nel.org>
Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/loongarch/include/asm/pgtable.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h
index 8ea57e2f0e04..79981ee8a171 100644
--- a/arch/loongarch/include/asm/pgtable.h
+++ b/arch/loongarch/include/asm/pgtable.h
@@ -355,7 +355,9 @@ static inline pte_t pte_mkdirty(pte_t pte)
 
 static inline pte_t pte_mkwrite(pte_t pte)
 {
-	pte_val(pte) |= (_PAGE_WRITE | _PAGE_DIRTY);
+	pte_val(pte) |= _PAGE_WRITE;
+	if (pte_val(pte) & _PAGE_MODIFIED)
+		pte_val(pte) |= _PAGE_DIRTY;
 	return pte;
 }
 
@@ -452,7 +454,9 @@ static inline int pmd_write(pmd_t pmd)
 
 static inline pmd_t pmd_mkwrite(pmd_t pmd)
 {
-	pmd_val(pmd) |= (_PAGE_WRITE | _PAGE_DIRTY);
+	pmd_val(pmd) |= _PAGE_WRITE;
+	if (pmd_val(pmd) & _PAGE_MODIFIED)
+		pmd_val(pmd) |= _PAGE_DIRTY;
 	return pmd;
 }
 
-- 
2.35.1