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X-CSE-ConnectionGUID: bDx6hyQgQW6nBfDPONGGHw== X-CSE-MsgGUID: 5ulhAyImR9i9JRaT3HJOTQ== X-IronPort-AV: E=McAfee;i="6800,10657,11533"; a="68970836" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68970836" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:29:43 -0700 X-CSE-ConnectionGUID: dPjkVayTRFCsnqA9Ybv36w== X-CSE-MsgGUID: H249bgJTR6CaQrcj46DBWQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169780586" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:29:23 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 12/19] x86: Minimal SLAB alignment Date: Mon, 25 Aug 2025 22:24:37 +0200 Message-ID: X-Mailer: git-send-email 2.50.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: a5mfwrwaa8xpajpjfiki5w7sno4s65rb X-Rspam-User: X-Rspamd-Queue-Id: 6848240007 X-Rspamd-Server: rspam05 X-HE-Tag: 1756153785-770279 X-HE-Meta: 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 FWGpCuky o7iqbKhb0mxvBtzuz58IShkUdsLki1JmcyzAslKMpng4089yLlpsfoQhNWHLxZ9GIMX37gwbpHir1Eys5ujzA88ruyaSQOH4SY4gzgKsOH+Zv5gxdrYhNKdI8Xih8q8oVAKyBcHk9SZx9jwNdkEU1LLbWhxtF4Emi0vLw++uYGf/io8R8t20hPxZePGfmQDDln2x/hHo/1PajO+v3UWoDoiKdPqUYo77Vi3q9I1C2xWGLmJ8qLpmN74uFs6fTZ2U8pube 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: 8 byte minimal SLAB alignment interferes with KASAN's granularity of 16 bytes. It causes a lot of out-of-bounds errors for unaligned 8 byte allocations. Compared to a kernel with KASAN disabled, the memory footprint increases because all kmalloc-8 allocations now are realized as kmalloc-16, which has twice the object size. But more meaningfully, when compared to a kernel with generic KASAN enabled, there is no difference. Because of redzones in generic KASAN, kmalloc-8' and kmalloc-16' object size is the same (48 bytes). So changing the minimal SLAB alignment of the tag-based mode doesn't have any negative impact when compared to the other software KASAN mode. Adjust x86 minimal SLAB alignment to match KASAN granularity size. Signed-off-by: Maciej Wieczor-Retman --- Changelog v4: - Extend the patch message with some more context and impact information. Changelog v3: - Fix typo in patch message 4 -> 16. - Change define location to arch/x86/include/asm/cache.c. arch/x86/include/asm/cache.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/include/asm/cache.h b/arch/x86/include/asm/cache.h index 69404eae9983..3232583b5487 100644 --- a/arch/x86/include/asm/cache.h +++ b/arch/x86/include/asm/cache.h @@ -21,4 +21,8 @@ #endif #endif +#ifdef CONFIG_KASAN_SW_TAGS +#define ARCH_SLAB_MINALIGN (1ULL << KASAN_SHADOW_SCALE_SHIFT) +#endif + #endif /* _ASM_X86_CACHE_H */ -- 2.50.1