The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ff1712f953e27f0b0718762ec17d0adb15c9fd0b Mon Sep 17 00:00:00 2001

From: Will Deacon will@kernel.org Date: Fri, 20 Nov 2020 13:57:48 +0000 Subject: [PATCH] arm64: pgtable: Ensure dirty bit is preserved across pte_wrprotect()

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

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 326c34677e86..5628289b9d5e 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -165,13 +165,6 @@ static inline pmd_t set_pmd_bit(pmd_t pmd, pgprot_t prot) return pmd; }

-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)); @@ -197,6 +190,20 @@ static inline pte_t pte_mkdirty(pte_t pte) 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)); @@ -846,12 +853,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres 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));