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([177.21.143.178]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73e25941fd9sm7925210b3a.53.2025.04.28.03.57.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Apr 2025 03:57:22 -0700 (PDT) From: Guilherme Giacomo Simoes To: akpm@linux-foundation.org Cc: andreyknvl@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pasha.tatashin@soleen.com, surenb@google.com, trintaeoitogc@gmail.com Subject: Re: [PATCH] mm: alloc_tag: change the KASAN_TAG_WIDTH for HW_TAGS Date: Mon, 28 Apr 2025 07:57:16 -0300 Message-Id: <20250428105716.151167-1-trintaeoitogc@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250427172551.fbf81f14d4e6563c13007a65@linux-foundation.org> References: <20250427172551.fbf81f14d4e6563c13007a65@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Andrew Morton wrote: > > the KASAN_TAG_WIDTH is 8 bits for both (HW_TAGS and SW_TAGS), but for > > HW_TAGS the KASAN_TAG_WIDTH can be 4 bits bits because due to the design > > of the MTE the memory words for storing metadata only need 4 bits. > > Change the preprocessor define KASAN_TAG_WIDTH for check if SW_TAGS is > > define, so KASAN_TAG_WIDTH should be 8 bits, but if HW_TAGS is define, > > so KASAN_TAG_WIDTH should be 4 bits. > > Why? > > I assume the effect is to save a few flags bits under some > circumstances? But that's just me guessing - please fully describe the > motivation and effects within changelogs. Ok, I will change the commit message with the "why", and send a v2. Thanks.