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Wed, 28 Oct 2026 10:16:59 -0400 (EDT) Date: Wed, 28 Oct 2026 14:16:58 +0000 From: Kiryl Shutsemau To: Peter Zijlstra Cc: Muchun Song , "David Hildenbrand (Arm)" , Andrew Morton , Matthew Wilcox , Usama Arif , Frank van der Linden , Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, Dave Hansen , Andy Lutomirski Subject: Re: [PATCHv7 13/18] mm: Drop fake head checks Message-ID: References: <070DDE5C-2183-4A8B-AC2D-891CAE15E581@linux.dev> <4A32F5E6-977D-4720-8723-B19AFBC08FCF@linux.dev> <7cb3dd91-f518-49b6-b311-9ec807b3c63b@linux.dev> <20261028080635.GD2668804@noisy.programming.kicks-ass.net> <20261028133439.GK2668804@noisy.programming.kicks-ass.net> X-Archived-By: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20261028133439.GK2668804@noisy.programming.kicks-ass.net> X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, Oct 28, 2026 at 02:34:39PM +0100, Peter Zijlstra wrote: > > Only architectures with HVO matter here: x86-64, riscv and loongarch. > > arm64 has had it disabled since 060a2c92d1b6. > > Per that commit, could it be re-enabled now that its no longer marked RO? No. The problem there is the PFN change on a live vmemmap PTE, which needs break-before-make on arm64. Dropping RO only removes the permission change. James Houghton is working on it with an Access Flag trick: https://lore.kernel.org/r/20261003002123.505555-1-jthoughton@google.com arm64 will need the writable tail too: its atomic_fetch_add_unless() is a CAS loop. -- Kiryl Shutsemau / Kirill A. Shutemov _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv