linux-kernel - [PATCH 2/2] arm64: mm: Always make sw-dirty PTEs hw-dirty in pte

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Message-ID: <20231204172646.2541916-3-jthoughton@google.com>
Date:   Mon,  4 Dec 2023 17:26:46 +0000
From:   James Houghton <jthoughton@...gle.com>
To:     Steve Capper <steve.capper@....com>, Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Ryan Roberts <ryan.roberts@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        James Houghton <jthoughton@...gle.com>
Subject: [PATCH 2/2] arm64: mm: Always make sw-dirty PTEs hw-dirty in pte_modify

Make it impossible to create a sw-dirty, hw-clean PTE with pte_modify.
Such a PTE should be impossible to create, and there may be places that
assume that pte_dirty() implies pte_hw_dirty().

Signed-off-by: James Houghton <jthoughton@...gle.com>

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index b19a8aee684c..79ce70fbb751 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -834,6 +834,12 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 		pte = set_pte_bit(pte, __pgprot(PTE_DIRTY));
 
 	pte_val(pte) = (pte_val(pte) & ~mask) | (pgprot_val(newprot) & mask);
+	/*
+	 * If we end up clearing hw dirtiness for a sw-dirty PTE, set hardware
+	 * dirtiness again.
+	 */
+	if (pte_sw_dirty(pte))
+		pte = pte_mkdirty(pte);
 	return pte;
 }
 
-- 
2.43.0.rc2.451.g8631bc7472-goog