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b=EhLEEUhu8ngvP04rcdO1wJ6msWZdfCnY5xxRLw/j/qz9RmVQey36HjQpIfxu/Nehk 44aoIxHUq3YL9Q1/FjhIR53EscyofY3edMGdLKzx4iSJTdnk2Td94s6P3VMXzkLpGP Wf6MIL7TvRBTcvlRAKzVSp5IqVoD97DGt7vgdx9WCppZa2PGwuLEs0nljOljWPwmsk wuApHQCHaO/eGv2m/snfRZ3E+3MOY9lCQTIXOvRKFrcbgtUUEBLKb5OaCwVbc/ZuXr ElqgLB9hZ0K8Bu1QWeTwQznvaCXcxXExxJONawuQuhelSSy303CUlmVDr4Es6VtZKH RYBOog/QFPn1Q== Date: Sun, 17 May 2026 21:59:05 +0300 From: Mike Rapoport To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , Ryan Roberts , Mark Rutland , Lorenzo Stoakes , Andrew Morton , David Hildenbrand , Linu Cherian , Usama Arif , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC V2 02/14] mm: Add read-write accessors for vm_page_prot Message-ID: References: <20260513044547.4128549-1-anshuman.khandual@arm.com> <20260513044547.4128549-3-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260513044547.4128549-3-anshuman.khandual@arm.com> X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0A25F120008 X-Stat-Signature: zze64mkf6cn8tip5yku3747uszsqtpi5 X-HE-Tag: 1779044354-517240 X-HE-Meta: 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 NnF71eFg 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, May 13, 2026 at 10:15:35AM +0530, Anshuman Khandual wrote: > Currently vma->vm_page_prot is safely read from and written to, without any > locks with READ_ONCE() and WRITE_ONCE(). But with introduction of D128 page > tables on arm64 platform, vm_page_prot grows to 128 bits which can't safely > be handled with READ_ONCE() and WRITE_ONCE(). > > Add read and write accessors for vm_page_prot like pgprot_[read|write]() > which any platform can override when required, although still defaulting as > READ_ONCE() and WRITE_ONCE(), thus preserving the functionality for others. > > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Lorenzo Stoakes > Cc: Mike Rapoport > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual Acked-by: Mike Rapoport (Microsoft) > --- > Changes in RFC V2: > > - Dropped _once from pgprot_[read|write]() callbacks per Mike > > include/linux/pgtable.h | 14 ++++++++++++++ > mm/huge_memory.c | 4 ++-- > mm/memory.c | 2 +- > mm/migrate.c | 2 +- > mm/mmap.c | 2 +- > 5 files changed, 19 insertions(+), 5 deletions(-) -- Sincerely yours, Mike.