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Fri, 20 Nov 2020 09:09:05 -0800 (PST) Date: Fri, 20 Nov 2020 09:09:03 -0800 From: Minchan Kim To: Will Deacon Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Catalin Marinas , Yu Zhao , Peter Zijlstra , Linus Torvalds , Anshuman Khandual , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org Subject: Re: [PATCH 2/6] arm64: pgtable: Ensure dirty bit is preserved across pte_wrprotect() Message-ID: <20201120170903.GC3377168@google.com> References: <20201120143557.6715-1-will@kernel.org> <20201120143557.6715-3-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201120143557.6715-3-will@kernel.org> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Nov 20, 2020 at 02:35:53PM +0000, Will Deacon wrote: > 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: It this stable material if it would be a problem once ARM64 supports softdirty in future? > Signed-off-by: Will Deacon > --- > arch/arm64/include/asm/pgtable.h | 27 ++++++++++++++------------- > 1 file changed, 14 insertions(+), 13 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 1bdf51f01e73..a155551863c9 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -162,13 +162,6 @@ 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)); > @@ -194,6 +187,20 @@ 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)); > @@ -843,12 +850,6 @@ 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)); > -- > 2.29.2.454.gaff20da3a2-goog >