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 04CB2C433F5 for ; Thu, 10 Mar 2022 16:47:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7CDD68D0002; Thu, 10 Mar 2022 11:47:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 77DA28D0001; Thu, 10 Mar 2022 11:47:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 61E058D0002; Thu, 10 Mar 2022 11:47:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0196.hostedemail.com [216.40.44.196]) by kanga.kvack.org (Postfix) with ESMTP id 4E7C88D0001 for ; Thu, 10 Mar 2022 11:47:56 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 09A129BBD0 for ; Thu, 10 Mar 2022 16:47:56 +0000 (UTC) X-FDA: 79229058552.20.9911431 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf10.hostedemail.com (Postfix) with ESMTP id 020B7C001B for ; Thu, 10 Mar 2022 16:47:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646930875; x=1678466875; h=message-id:date:mime-version:to:cc:references:from: subject:in-reply-to:content-transfer-encoding; bh=X3+zmRgSG8D741YzWGvezJvJbaSBg+0aX7D4WHq+ZgE=; b=QDnEwP2fc6kf55ebsl6Rev+/8nzhOCSZ447gq9TqAVxNs8aD1AnUNGNy LvCBr4Eal4sbzgOUTKT6VYcZxbIb082s0V1h0gwbaLiusUZD2ioUOqTSU AuwpO3x3jBip1bo+WZEV6PtHwD0F43o/c848jw2rhe+EpkFpjQuDRO32U MDs3gSvYUKM6j0v+vDtoG4NL5NOiA+7o0K7Dt1ToO1YXtmZ/+nFQcJQD3 QF2PDJ5lU/n4ItnVsTB15iIA3JuzlOK+UEuY5PXGsLIv8g6b4C6S7N7VO Z9iHwzh9lHi6db9iDBxzu/Io7fh01rdRFZWlm4xqluT+Ha3sGM5BpxSOe Q==; X-IronPort-AV: E=McAfee;i="6200,9189,10282"; a="280039275" X-IronPort-AV: E=Sophos;i="5.90,171,1643702400"; d="scan'208";a="280039275" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2022 08:45:52 -0800 X-IronPort-AV: E=Sophos;i="5.90,171,1643702400"; d="scan'208";a="688715724" Received: from efrantz-mobl1.amr.corp.intel.com (HELO [10.212.252.101]) ([10.212.252.101]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2022 08:45:51 -0800 Message-ID: <286efdb9-7dbf-82f3-b172-29c575a3791b@intel.com> Date: Thu, 10 Mar 2022 08:45:44 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Content-Language: en-US To: David Laight , 'Bharata B Rao' , "linux-kernel@vger.kernel.org" Cc: "linux-mm@kvack.org" , "x86@kernel.org" , "kirill.shutemov@linux.intel.com" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "shuah@kernel.org" , "oleg@redhat.com" , "ananth.narayan@amd.com" References: <20220310111545.10852-1-bharata@amd.com> <699fb763ac054833bc8c29c9814c63b2@AcuMS.aculab.com> From: Dave Hansen Subject: Re: [RFC PATCH v0 0/6] x86/AMD: Userspace address tagging In-Reply-To: <699fb763ac054833bc8c29c9814c63b2@AcuMS.aculab.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 020B7C001B X-Rspam-User: Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=QDnEwP2f; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf10.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 192.55.52.88) smtp.mailfrom=dave.hansen@intel.com X-Stat-Signature: 45uqk8dgapcox6p346puesgdojcjboe4 X-HE-Tag: 1646930874-871199 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 3/10/22 06:32, David Laight wrote: >> UAI allows software to store a tag in the upper 7 bits of a logical >> address [63:57]. When enabled, the processor will suppress the >> traditional canonical address checks on the addresses. More information >> about UAI can be found in section 5.10 of 'AMD64 Architecture >> Programmer's Manual, Vol 2: System Programming' which is available from >> >> https://bugzilla.kernel.org/attachment.cgi?id=300549 > Is that really allowing bit 63 to be used? > That is normally the user-kernel bit. > I can't help feeling that will just badly break things. Yeah, this does seem worrisome. The LAM approach[1] retains canonicality checking for bit 63. 1. https://www.intel.com/content/www/us/en/develop/download/intel-architecture-instruction-set-extensions-programming-reference.html