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 12BCEC433EF for ; Thu, 10 Mar 2022 16:48:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244436AbiCJQtj (ORCPT ); Thu, 10 Mar 2022 11:49:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244263AbiCJQtb (ORCPT ); Thu, 10 Mar 2022 11:49:31 -0500 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 55FA9E0AD7 for ; Thu, 10 Mar 2022 08:48:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646930901; x=1678466901; h=message-id:date:mime-version:to:cc:references:from: subject:in-reply-to:content-transfer-encoding; bh=X3+zmRgSG8D741YzWGvezJvJbaSBg+0aX7D4WHq+ZgE=; b=F2Il/JXXsnLNgcbHexxhUTEq0BxumhuP0UMkY9JYBfCF1kjVDncNs5rY HoShbf1lXoba4gLD9FcbUCSsk2gkaTCaz5jk33yITkwFpuq2EGJy/CGPe YS3prOxLzohlMcd6r8Gmd9sDW7jWbvuet3GY3Iu1F3Z9Dt9N7vAwLijSp FM4V09BJSROFz8dKLGzXJsKWzAAeHHjfb0rYG0Qrk9EeAY16po83RtrcL UjerW6WecCaxoAsRumlvDQdFz3A1SBSW+QGhbz4rdheFYMMmcVSr8qe+V 8FTNwV5vH4rb8DMj94GeT8CmlNPqrmJVsonmCRnIkqAj1pPaluqTtlAI3 A==; X-IronPort-AV: E=McAfee;i="6200,9189,10282"; a="341730528" X-IronPort-AV: E=Sophos;i="5.90,171,1643702400"; d="scan'208";a="341730528" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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