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Tue, 19 Sep 2023 17:56:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695146192; bh=oTw5IJcJ7n9tX0eMkW/N8Wz1esHYNZcEC42vs2lJXvE=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=XLFPSlnvSySUE75ZgJvK7r8LybpP+ITsN9JtmBGN6EMLqQ2W1A7Ej1jHgZg+f8J86 RZPgO15umwMmwDOfWjUoLHbUcxxJkDLD7EtjO2CyQYaT2AHNgMajuzciDetfw1hKNX HqQqI3N5SreMRdLI43zCtjAfTgRWJSVMSqqmsKw7MvXP1AjkJrW3Y2K0rfa6IOyg+W UZhRvKxUeKOTEbcuIGDSIa1wQkoY9MdVjUBP5hgBnOeCQxiGF3nvd1jlbDblEOXUnn Vl7gRXEjSWgSLt5s/0OlNOpmkV7LiNq4PU5hVbOaHwEK/QLU23W5CCw1xzhsP+wRNc OeCwbk6WH+wBQ== Date: Tue, 19 Sep 2023 10:56:30 -0700 From: Kees Cook To: Dave Hansen , Matteo Rizzo , Linus Torvalds CC: Ingo Molnar , "Lameter, Christopher" , penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, corbet@lwn.net, luto@kernel.org, peterz@infradead.org, jannh@google.com, evn@google.com, poprdi@google.com, jordyzomer@google.com Subject: =?US-ASCII?Q?Re=3A_=5BRFC_PATCH_00/14=5D_Prevent_cross?= =?US-ASCII?Q?-cache_attacks_in_the_SLUB_allocator?= User-Agent: K-9 Mail for Android In-Reply-To: <782b131a-c3b9-7679-824a-70625c966def@intel.com> References: <20230915105933.495735-1-matteorizzo@google.com> <7a4f5128-28fd-3c5f-34c2-1c34f4448174@intel.com> <1d7573c0-ebbc-6ed2-f152-1045eb0542f9@os.amperecomputing.com> <782b131a-c3b9-7679-824a-70625c966def@intel.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: DF3DC1C000B X-Stat-Signature: 9yre3te9frcohhzkpk9yb6gmr38m6ubj X-Rspam-User: X-HE-Tag: 1695146193-812706 X-HE-Meta: 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 u6j1ohwZ oVQTuELtRqMDUvAa1mUdNODRFUK8AenjhCzYr+ZWM1/atwOG3oG9uc+NA7S9ONRxKMKjNx1Q4G2sTWq3CqaIhbMvlwZMDPkayx+4lWckGmZlx39KddN3tjuHhM4tfcovOARkRdL5rpj4qN4MmRZp99KoOymO9Ee2giPFqfLoPiuJKvqc0gOlzIn9v8CtHdVzR+dB84Jv7cr7nOo9GbSoDbvFxdSXMY7dPv+czlDca4gI9xeljPoDN9KH+NUoYwNhFZSfl2hCEDB4HKk7TVNqlcHvvC4fWFz6v5msDUJe9BQ8upMVY85vhjRpIx7n2838hpTyCpZAk6//cUQt3BWJCrVJicJCwv7IuUFRDu+YS7seDbTJk+2zogP3i04Lw4vHQ40vJr8jt6S7IyYHON9f4SdK/nL6ZTiO6JVfhWmdWptSAjOUQ8la1Gaa0XrIVoNGj9D0D 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: On September 19, 2023 9:02:07 AM PDT, Dave Hansen wrote: >On 9/19/23 08:48, Matteo Rizzo wrote: >>> I think the whole "make it one single compile-time option" model is >>> completely and fundamentally broken=2E >> Wouldn't making this toggleable at boot time or runtime make performanc= e >> even worse? > >Maybe=2E > >But you can tolerate even more of a performance impact from a feature if >the people that don't care can actually disable it=2E > >There are also plenty of ways to minimize the overhead of switching it >on and off at runtime=2E Static branches are your best friend here=2E Let's start with a boot time on/off toggle (no per-slab, no switch on out-= of-space, etc)=2E That should be sufficient for initial ease of use for tes= ting, etc=2E But yes, using static_branch will nicely DTRT here=2E --=20 Kees Cook