From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1427340AbcBTAeF (ORCPT ); Fri, 19 Feb 2016 19:34:05 -0500 Received: from outbound.smtp.vt.edu ([198.82.183.121]:42598 "EHLO omr1.cc.vt.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1422970AbcBTAeD (ORCPT ); Fri, 19 Feb 2016 19:34:03 -0500 X-Mailer: exmh version 2.8.0 04/21/2012 with nmh-1.6+dev To: Paolo Bonzini Cc: Aurelien Jarno , Gleb Natapov , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Aruna Hewapathirane Subject: Re: Silence compiler warning in arch/x86/kvm/emulate.c From: Valdis.Kletnieks@vt.edu In-Reply-To: <56C75735.3010602@redhat.com> References: <142668.1440884956@turing-police.cc.vt.edu> <20160219111139.GA22041@aurel32.net> <20160219164548.GA28630@aurel32.net> <10537.1455904440@turing-police.cc.vt.edu> <56C75735.3010602@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1455928424_2428P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Fri, 19 Feb 2016 19:33:44 -0500 Message-ID: <19233.1455928424@turing-police.cc.vt.edu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --==_Exmh_1455928424_2428P Content-Type: text/plain; charset=us-ascii On Fri, 19 Feb 2016 18:56:05 +0100, Paolo Bonzini said: > On 19/02/2016 18:54, Valdis.Kletnieks@vt.edu wrote: > > But under what conditions is 'la' a 64-bit quantity that has any > > bits set in the high 32 bits (meaning it's a pointer to something > > over the 4G line) - but it's still valid to smash those bits? > > That can happen for example if there is a non-zero segment base. Then > the linear address wraps at 4G. Gaah. Obviously, the concept that software could actually depend on a segment base pointing at the 3G line (or whatever) to wrap around and be used to address memory down in the first gig of RAM was too bizarre for my brain to visualize. :) The IBM S/360 with 24 bit addresses and S/370 with 24 or 31 bit addresses would allow some instructions (most famously MVCL Move Character Long) to start operating at the high end of memory and wrap around to the beginning. The system documentation was pretty clear that although this *worked*, it was probably not what you actually wanted to do.... :) --==_Exmh_1455928424_2428P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Exmh version 2.5 07/13/2001 iQIVAwUBVse0aAdmEQWDXROgAQJMXA//RM0pFV2m1cGE9yP2ZhXTf3mlb86YNpmF NYh5wof4E6395uHeo7vpZko4jq7spXeUeyRwh76OqJ8KCpCZXEWJceCCfmopuR6a 9cuWDcbrqi6sG0Vemgo7CeLomBThPvlB+sTRYZ0APeGxF3MYFYvoJpXk9Umx8OGQ ioDWy3yzp+WtMtfotD5+VqyXkEOMKuSW+AjWxpPQR+tBCXAfchckj+kgZHUYAUYl 0JCwi87hUFpmHvrzj6wIIwq+rc88DmMso1SF0A9lAA0K8kY4wwr2H7g/kPe5AwWh jkkM3Kmt3X3wj2T4lrttsa7I4L3dfJ/MK7pdmPR4lndsw/ODNbiDSVr8lcYSUHbG GrPPawPe3FsW65g6zIu3QpYYuFhRqQWxBVe598ESV+2ogH9ZPm1Ahzb6lH1r4lrP b8EKKD8vzz3rlLL4Aek4WId5aiM9IPGsl0N9sJ5pwBJTuXCIaVMDRv6fEX2OJo11 U3ejLnyCaoVPZVI44Uek7QBjhD5N7ouAXNbzVzK6L8G1MSHfK3J5BXFdF1epMpt8 ULwosBEuCfpPE+99wxchJSbeRk/wb13i0wD2y65qjTBZInkRctAlbWighEtHRSa1 +ui9nJyOk59ug0xldbE6Y7WeRgkXoeWvsiv7bfwDfs3ylieGRgIvT2Znbv6DoalO vk0pcpFIc4I= =ei/W -----END PGP SIGNATURE----- --==_Exmh_1455928424_2428P--