From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDAE7CE79A9 for ; Tue, 19 Sep 2023 16:06:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229969AbjISQGV (ORCPT ); Tue, 19 Sep 2023 12:06:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229590AbjISQGV (ORCPT ); Tue, 19 Sep 2023 12:06:21 -0400 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 903609D; Tue, 19 Sep 2023 09:06:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1695139575; x=1726675575; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=m9SJWOh+sBbmoBDHuJDTvYjtZel5Tu2jwPotxz7MjXY=; b=hUmE/qXZSiQD+5XsknaEFo0x2rsll9vKPCfvl9ONYITWx+H9YLLoCqZS qKaVaY+AK22EzNm0VkDF5l9s5YV8zHIB1+5J0AOvaVNd6gEI/M3uLE1Me pj1KWt133UHBj3q+Il4a6uS8SWKaz2SfJcZSmFT3C4KJWufaF6YdCM4KR CGLy8WpeKzxGktRfoYftpcjZ8axJ23ggJFEfTmj/BV/zdgOM+NRlb3eNL efzjLXF76bSsnqJpYfA1YpSisgmv+ASJBL4JFypZpotDTIM4AV/19fyY1 qmMKbJF5CgkficBqOjgol+qZyA80aS1tEAz5fGQuryHmFM50/3yB+C627 w==; X-IronPort-AV: E=McAfee;i="6600,9927,10838"; a="410908993" X-IronPort-AV: E=Sophos;i="6.02,160,1688454000"; d="scan'208";a="410908993" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Sep 2023 09:02:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10838"; a="746294853" X-IronPort-AV: E=Sophos;i="6.02,160,1688454000"; d="scan'208";a="746294853" Received: from rdromms-mobl4.amr.corp.intel.com (HELO [10.212.158.204]) ([10.212.158.204]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Sep 2023 09:02:08 -0700 Message-ID: <782b131a-c3b9-7679-824a-70625c966def@intel.com> Date: Tue, 19 Sep 2023 09:02:07 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [RFC PATCH 00/14] Prevent cross-cache attacks in the SLUB allocator Content-Language: en-US To: 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 References: <20230915105933.495735-1-matteorizzo@google.com> <7a4f5128-28fd-3c5f-34c2-1c34f4448174@intel.com> <1d7573c0-ebbc-6ed2-f152-1045eb0542f9@os.amperecomputing.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 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. > Wouldn't making this toggleable at boot time or runtime make performance > even worse? Maybe. But you can tolerate even more of a performance impact from a feature if the people that don't care can actually disable it. There are also plenty of ways to minimize the overhead of switching it on and off at runtime. Static branches are your best friend here.