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Sat, 22 Feb 2025 07:06:45 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Andrey Konovalov Date: Sat, 22 Feb 2025 16:06:34 +0100 X-Gm-Features: AWEUYZkJMUGTJnf0tyUt8lWwOa_mEt-qqEj8jwlDkAHHUkPqAhs2iK4gMtYGacQ Message-ID: Subject: Re: [PATCH v2 14/14] x86: Make software tag-based kasan available To: Maciej Wieczor-Retman Cc: kees@kernel.org, julian.stecklina@cyberus-technology.de, kevinloughlin@google.com, peterz@infradead.org, tglx@linutronix.de, justinstitt@google.com, catalin.marinas@arm.com, wangkefeng.wang@huawei.com, bhe@redhat.com, ryabinin.a.a@gmail.com, kirill.shutemov@linux.intel.com, will@kernel.org, ardb@kernel.org, jason.andryuk@amd.com, dave.hansen@linux.intel.com, pasha.tatashin@soleen.com, ndesaulniers@google.com, guoweikang.kernel@gmail.com, dwmw@amazon.co.uk, mark.rutland@arm.com, broonie@kernel.org, apopple@nvidia.com, bp@alien8.de, rppt@kernel.org, kaleshsingh@google.com, richard.weiyang@gmail.com, luto@kernel.org, glider@google.com, pankaj.gupta@amd.com, pawan.kumar.gupta@linux.intel.com, kuan-ying.lee@canonical.com, tony.luck@intel.com, tj@kernel.org, jgross@suse.com, dvyukov@google.com, baohua@kernel.org, samuel.holland@sifive.com, dennis@kernel.org, akpm@linux-foundation.org, thomas.weissschuh@linutronix.de, surenb@google.com, kbingham@kernel.org, ankita@nvidia.com, nathan@kernel.org, ziy@nvidia.com, xin@zytor.com, rafael.j.wysocki@intel.com, andriy.shevchenko@linux.intel.com, cl@linux.com, jhubbard@nvidia.com, hpa@zytor.com, scott@os.amperecomputing.com, david@redhat.com, jan.kiszka@siemens.com, vincenzo.frascino@arm.com, corbet@lwn.net, maz@kernel.org, mingo@redhat.com, arnd@arndb.de, ytcoode@gmail.com, xur@google.com, morbo@google.com, thiago.bauermann@linaro.org, linux-doc@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1C495A0019 X-Stat-Signature: wycm5cofmuxooo3qbod3zc6afcew1hex X-Rspam-User: X-HE-Tag: 1740236806-796746 X-HE-Meta: U2FsdGVkX1872qKISCrEVfV2B93xdNSFzHkEIAOlZwvL4Dm1nW34M6C9nyRI/FNDwXyVvO+exzsFV16Gx+Y5OmoIHpw8d5d6PZhYxrNA95fYyMSqZKpBSJZAjoOFMMrxA1yLtdhWstKUOuSCm+vtUABeUpqolBaDVywmSQcRS3MsJ7pxj+i2wZl1yS12SuNI6dK6GvmGYwVoYRn4XruyUJvYq4j132AcuL33y348Eqjt8iV6vJchgju1/PV0M9Tn0djvjGO8pPNm29NMEgd/kDkYT0vCs58WZllHHgpE/Kti2OGs/mCwsyz0E+7eq5kg7JDHzLzfS1CCKLbJetxO7PyUyRrpSrWpwCAAf4L6xqcq+6N4z9JbDlaJQ1mt7HwbHAY/bkDwhMlZy6pLHTjB6Oiw0zK7H0NHH+Lg2VKOzCsZrOBr3HTdKo/tDmVvhGW0Z195+vkCk+7/UCHdkYX6i9IMz/ZxpjBGNsNYjzlI5ZkQCfqQTW3AsmrHcCrReHIO3HlioDoZ4gRX/RVQVMd3NN+hRrptv8SvgjyTM1xjZFkCPASWeMVqDlre1tSNgUjuUmQ8vn9iUCoOZLhD9zAA94Uc12TZ5uiJOnYVn/TTbbnicVvRkvmL/1afnlfbZNmpve3LRpy/p110n4OYCkrdWqjWA8/JBZMez431xO24xdbsdzpmmcEYHzrXbUjLGMBXor1YTwZg+fE5UC3LJFBrgl9YMXdl6jnvYyalesW6HPJWoVDInkeDbkwzZ6h+21LgSL7DALe3DAQhlicLB9Xma/Yp/g9ii2jtmcDbGGSS5uB/wvLyU4hhimrLLBxPuqCe9TXcuirmrkm0jSHzpzW6/0xG80CPZL0Ot5FaGz+1kGmgyQ6yIcYbuF4fyfXdmudAVKW021RPXGxPgoOmRncVe6mSdjbggoGSF5anC7zNKDSnFuv8JfzqDlt+M5XOVRhNdRH4puhrEmZVc/mKYyf YrjwzvYX 1db7S+dNn9ok10LbKNtBM+eZ2cvT1p6VKi/vVMr+BT6vHyj1IehgWtuVmWPMI9eehGTjKsH7wjVh8Z/PMR7qiRoovI854tY8ociS8qyF1wXpCZYaWCZ/Y64H3kbJrTpgP+oj/ovApSdfBbBMgu7gvX5HJWHmBKqpBMC/58SuJndmV9V0YQFderV5Q/Qi8bN6nb6/HHuf9h9h90l1dkMkSxodTnXCZgzDGIM7aipgLjaeYAr0BBaJ4eNA2ZVbXbpmM3CtnMhUW7LFrkD63wfJBFjECjpm+K7+a3vY0y/nTclbI5JlbUSxOvQq6Due3+b8MzbJ4724dSykVJRbM75qInOb/YM+M2LJgp+TP1rvxWMJ1mDVilkF8KN7fXQQfSjYfIlTntc/kBZ/DqVaBbC+J+UiqHPwZImZ0fje1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000129, 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, Feb 21, 2025 at 3:45=E2=80=AFPM Maciej Wieczor-Retman wrote: > > >What's the purpose of this config option? I think we can just change > >the value of the KASAN_SHADOW_SCALE_SHIFT define when KASAN_SW_TAGS is > >enabled. > > Well, I was aiming at later adding the "default 5 if KASAN_SW_TAGS_DENSE"= , and > this way it would look much cleaner than the: > > if KASAN_SW_TAGS > if KASAN_SW_TAGS_DENSE > KASAN_SHADOW_SCALE_SHIFT =3D 5 > else > KASAN_SHADOW_SCALE_SHIFT =3D 4 > else > KASAN_SHADOW_SCALE_SHIFT =3D 3 I think this is fine. It's still better than adding a non-configurable config option. > But now that I think of it, it should be possible to overwrite the > KASAN_SHADOW_SCALE_SHIFT from non-arch code if dense mode is enabled. This should also work. Especially since the dense mode will probably work for arm64 as well. But let's keep this series self-contained. > That's a topic for the next series but I'd imagine all architectures woul= d > normally use the 16 memory bytes / shadow byte and if they'd care for the= dense > mode they'd go for 32 memory bytes / shadow byte. Or do you think that's = a > faulty assumption? Probably, but for sure I don't know, not that many architectures that care about memory tagging yet :)