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Miller" , Dave Hansen , David Hildenbrand , Dinh Nguyen , Geert Uytterhoeven , Guo Ren , Heiko Carstens , Helge Deller , Huacai Chen , Ingo Molnar , Johannes Berg , John Paul Adrian Glaubitz , Jonathan Corbet , "Liam R. Howlett" , Lorenzo Stoakes , Magnus Lindholm , Matt Turner , Max Filippov , Michael Ellerman , Michal Hocko , Michal Simek , Muchun Song , Oscar Salvador , Palmer Dabbelt , Pratyush Yadav , Richard Weinberger , Stafford Horne , Suren Baghdasaryan , Thomas Bogendoerfer , Thomas Gleixner , Vasily Gorbik , Vineet Gupta , Vlastimil Babka , Will Deacon , x86@kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-cxl@vger.kernel.org, linux-doc@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-um@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev, sparclinux@vger.kernel.org Subject: Re: [PATCH 3.5] arm: make initialization of zero page independent of the memory map (was Re: [PATCH v2 22/28] arch, mm: consolidate initialization of nodes, zones and memory map) Message-ID: References: <20260102070005.65328-1-rppt@kernel.org> <20260102070005.65328-23-rppt@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: csk3peu3dyj6wa91ndrc9epbxiysy7sw X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 074BC40004 X-HE-Tag: 1767560295-926599 X-HE-Meta: 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 +yp6KYSo 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 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: List-Subscribe: List-Unsubscribe: On Sun, Jan 04, 2026 at 02:01:40PM +0200, Mike Rapoport wrote: > From 35d016bbf5da7c08cc5c5547c85558fc50cb63aa Mon Sep 17 00:00:00 2001 > From: Klara Modin > Date: Sat, 3 Jan 2026 20:40:09 +0200 > Subject: [PATCH] arm: make initialization of zero page independent of the > memory map > > Unlike most architectures, arm keeps a struct page pointer to the > empty_zero_page and to initialize it requires conversion of a virtual > address to page which makes it necessary to have memory map initialized > before creating the empty_zero_page. > > Make empty_zero_page a stataic array in BSS to decouple it's > initialization from the initialization of the memory map. I see you haven't considered _why_ ARM does this. You are getting rid of the flush_dcache_page() call, which ensures that the zeroed contents of the page are pushed out of the cache into memory. This is necessary. BSS is very similar. It's memset() during the kernel boot _after_ the caches are enabled. Without an explicit flush, nothing guarantees that those writes will be visible to userspace. To me, this seems like a bad idea, which will cause userspace to break. We need to call flush_dcache_page(), and _that_ requires a struct page. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!