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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3c5393b797csm5054822f8f.39.2025.08.22.05.07.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Aug 2025 05:07:25 -0700 (PDT) Date: Fri, 22 Aug 2025 13:04:20 +0100 From: David Laight To: Christophe Leroy Cc: Michael Ellerman , Nicholas Piggin , Madhavan Srinivasan , Alexander Viro , Christian Brauner , Jan Kara , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Darren Hart , Davidlohr Bueso , "Andre Almeida" , Andrew Morton , Dave Hansen , Linus Torvalds , Daniel Borkmann , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org Subject: Re: [PATCH v2 09/10] powerpc/32: Automatically adapt TASK_SIZE based on constraints Message-ID: <20250822130420.6c6a3fce@pumpkin> In-Reply-To: References: X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: D6C8D40003 X-Stat-Signature: did1yrxq96is8rwtewy3q7iboza99ebe X-HE-Tag: 1755864447-393251 X-HE-Meta: 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 mI2VIPmF 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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 Fri, 22 Aug 2025 11:58:05 +0200 Christophe Leroy wrote: > At the time being, TASK_SIZE can be customized by the user via Kconfig > but it is not possible to check all constraints in Kconfig. Impossible > setups are detected at compile time with BUILD_BUG() but that leads > to build failure when setting crazy values. It is not a problem on its > own because the user will usually either use the default value or set > a well thought value. However build robots generate crazy random > configs that lead to build failures, and build robots see it as a > regression every time a patch adds such a constraint. > > So instead of failing the build when the custom TASK_SIZE is too > big, just adjust it to the maximum possible value matching the setup. > > Several architectures already calculate TASK_SIZE based on other > parameters and options. > > In order to do so, move MODULES_VADDR calculation into task_size_32.h > and ensure that: > - On book3s/32, userspace and module area have their own segments (256M) > - On 8xx, userspace has its own full PGDIR entries (4M) > > Then TASK_SIZE is garantied to be correct so remove related ^ guaranteed > BUILD_BUG()s.