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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Subject: [PATCH 5.9 034/152] arm64: pgtable: Ensure dirty bit is preserved across pte_wrprotect()
Date:   Tue,  1 Dec 2020 09:52:29 +0100
Message-Id: <20201201084716.355027108@linuxfoundation.org>
In-Reply-To: <20201201084711.707195422@linuxfoundation.org>
References: <20201201084711.707195422@linuxfoundation.org>
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From: Will Deacon <will@kernel.org>

commit ff1712f953e27f0b0718762ec17d0adb15c9fd0b upstream.

With hardware dirty bit management, calling pte_wrprotect() on a writable,
dirty PTE will lose the dirty state and return a read-only, clean entry.

Move the logic from ptep_set_wrprotect() into pte_wrprotect() to ensure that
the dirty bit is preserved for writable entries, as this is required for
soft-dirty bit management if we enable it in the future.

Cc: <stable@vger.kernel.org>
Fixes: 2f4b829c625e ("arm64: Add support for hardware updates of the access and dirty pte bits")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20201120143557.6715-3-will@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/include/asm/pgtable.h |   27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -146,13 +146,6 @@ static inline pte_t set_pte_bit(pte_t pt
 	return pte;
 }
 
-static inline pte_t pte_wrprotect(pte_t pte)
-{
-	pte = clear_pte_bit(pte, __pgprot(PTE_WRITE));
-	pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
-	return pte;
-}
-
 static inline pte_t pte_mkwrite(pte_t pte)
 {
 	pte = set_pte_bit(pte, __pgprot(PTE_WRITE));
@@ -178,6 +171,20 @@ static inline pte_t pte_mkdirty(pte_t pt
 	return pte;
 }
 
+static inline pte_t pte_wrprotect(pte_t pte)
+{
+	/*
+	 * If hardware-dirty (PTE_WRITE/DBM bit set and PTE_RDONLY
+	 * clear), set the PTE_DIRTY bit.
+	 */
+	if (pte_hw_dirty(pte))
+		pte = pte_mkdirty(pte);
+
+	pte = clear_pte_bit(pte, __pgprot(PTE_WRITE));
+	pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));
+	return pte;
+}
+
 static inline pte_t pte_mkold(pte_t pte)
 {
 	return clear_pte_bit(pte, __pgprot(PTE_AF));
@@ -799,12 +806,6 @@ static inline void ptep_set_wrprotect(st
 	pte = READ_ONCE(*ptep);
 	do {
 		old_pte = pte;
-		/*
-		 * If hardware-dirty (PTE_WRITE/DBM bit set and PTE_RDONLY
-		 * clear), set the PTE_DIRTY bit.
-		 */
-		if (pte_hw_dirty(pte))
-			pte = pte_mkdirty(pte);
 		pte = pte_wrprotect(pte);
 		pte_val(pte) = cmpxchg_relaxed(&pte_val(*ptep),
 					       pte_val(old_pte), pte_val(pte));