Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755554Ab3DJSdL (ORCPT ); Wed, 10 Apr 2013 14:33:11 -0400 Received: from terminus.zytor.com ([198.137.202.10]:33681 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751623Ab3DJSdJ (ORCPT ); Wed, 10 Apr 2013 14:33:09 -0400 Message-ID: <5165AF30.909@zytor.com> Date: Wed, 10 Apr 2013 11:28:00 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Jan Beulich CC: Alexander Duyck , Jeremy Fitzhardinge , Alex Shi , Will Drewry , Kees Cook , Julien Tinnes , "kernel-hardening@lists.openwall.com" , Frederic Weisbecker , Dan Rosenberg , "x86@kernel.org" , Borislav Petkov , Steven Rostedt , "virtualization@lists.linux-foundation.org" , "xen-devel@lists.xensource.com" , Konrad Rzeszutek Wilk , "Paul E. McKenney" , Ingo Molnar , LKML Subject: Re: [Xen-devel] Readonly GDT References: <20130408224328.GA17641@www.outflux.net> <51634935.9010905@zytor.com> <51645D6F.7070705@zytor.com> <51646054.3090509@zytor.com> <5164B5BD.5050702@zytor.com> <5165502902000078000CC022@nat28.tlf.novell.com> In-Reply-To: <5165502902000078000CC022@nat28.tlf.novell.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1035 Lines: 27 On 04/10/2013 02:42 AM, Jan Beulich wrote: > >> However, the packing solution has the advantage of reducing address >> space consumption which matters on 32 bits: even on i386 we can easily >> burn a megabyte of address space for 4096 processors, but burning 16 >> megabytes starts to hurt. > > Packing would have the additional benefit of Xen not needing to > become a special case in yet another area (because pages > containing live descriptor table entries need to be read-only for > PV guests, and need to consist of only descriptor table entries). > OK, so on 64 bits this sounds like a win all around, whereas it is not feasible on 32 bits (which means we don't really need to worry about burning address space.) So, anyone interested in implementing this for 64 bits? -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/