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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3543FC433FE for ; Thu, 12 May 2022 21:51:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 558E76B0073; Thu, 12 May 2022 17:51:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 507C76B0075; Thu, 12 May 2022 17:51:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3A8FB6B0078; Thu, 12 May 2022 17:51:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 28D746B0073 for ; Thu, 12 May 2022 17:51:52 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id E25C361558 for ; Thu, 12 May 2022 21:51:51 +0000 (UTC) X-FDA: 79458438822.28.27A9782 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf30.hostedemail.com (Postfix) with ESMTP id CCA23800A6 for ; Thu, 12 May 2022 21:51:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1652392309; x=1683928309; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=mUHbs3CGqeDWe+cfjYsXwi1cDVhyW8WsG1CjemSY2+o=; b=MM73c3Qn/mMKfiOvataRMKIrv/jE25T52bsTzxbnx4L4sHI/hDSGL0B1 1Q9ZIXv76/bURRiishFuDhBcCOIvxVYkc6Uj2anwpi6HXtvCwtIRz9SjK Isvg+iHDqDX4aXS6HfRnNVOznXvZjvUhnkZmTIXzmaqUYlZOk/gzZgO7t 8yD69eyvOfv9YQMtEI15mue752oOrpX2M+PpKQek90/akCt2976i3OffK +uQTgdGFIxvprkuxYbCayVKS7qqBkLmLXf1+bibaKPCWKLbJv9g9PAnay oTqVnAhegQG1P71CDVy7+r4IENN3wNwMVYeJa1LSwCN0GFJDhaPjo/Q69 w==; X-IronPort-AV: E=McAfee;i="6400,9594,10345"; a="333179637" X-IronPort-AV: E=Sophos;i="5.91,221,1647327600"; d="scan'208";a="333179637" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 May 2022 14:51:33 -0700 X-IronPort-AV: E=Sophos;i="5.91,221,1647327600"; d="scan'208";a="572707221" Received: from wdwickar-mobl1.amr.corp.intel.com (HELO [10.252.130.245]) ([10.252.130.245]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 May 2022 14:51:32 -0700 Message-ID: <55176b79-90af-4a47-dc06-9f5f2f2c123d@intel.com> Date: Thu, 12 May 2022 14:51:31 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [RFCv2 00/10] Linear Address Masking enabling Content-Language: en-US To: Thomas Gleixner , Peter Zijlstra , "Kirill A. Shutemov" Cc: Dave Hansen , Andy Lutomirski , x86@kernel.org, Alexander Potapenko , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220511022751.65540-1-kirill.shutemov@linux.intel.com> <20220511064943.GR76023@worktop.programming.kicks-ass.net> <20bada85-9203-57f4-2502-57a6fd11f3ea@intel.com> <875ymav8ul.ffs@tglx> From: Dave Hansen In-Reply-To: <875ymav8ul.ffs@tglx> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=MM73c3Qn; spf=none (imf30.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 134.134.136.100) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CCA23800A6 X-Stat-Signature: 3u4t1fihsrqat6h5qq6sfncchpio5ihw X-HE-Tag: 1652392289-798986 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 5/12/22 12:39, Thomas Gleixner wrote: >> It's OK for a debugging build that runs on one kind of hardware. But, >> if we want LAM-using binaries to be portable, we have to do something >> different. >> >> One of the stated reasons for adding LAM hardware is that folks want to >> use sanitizers outside of debugging environments. To me, that means >> that LAM is something that the same binary might run with or without. > On/off yes, but is there an actual use case where such a mechanism would > at start time dynamically chose the number of bits? I'd love to hear from folks doing the userspace side of this. Will userspace be saying: "Give me all the bits you can!". Or, will it really just be looking for 6 bits only, and it doesn't care whether it gets 6 or 15, it will use only 6? Do the sanitizers have more overhead with more bits? Or *less* overhead because they can store more metadata in the pointers? Will anyone care about the difference about potentially missing 1/64 issues with U57 versus 1/32768 with U48?