From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754516AbaIDObu (ORCPT ); Thu, 4 Sep 2014 10:31:50 -0400 Received: from mail.emea.novell.com ([130.57.118.101]:49577 "EHLO mail.emea.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752221AbaIDObt convert rfc822-to-8bit (ORCPT ); Thu, 4 Sep 2014 10:31:49 -0400 Message-Id: <540893F00200007800030E4F@mail.emea.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.0.1 Date: Thu, 04 Sep 2014 15:31:44 +0100 From: "Jan Beulich" To: "Andrew Cooper" Cc: "David Vrabel" , , , , "Juergen Gross" , Subject: Re: [Xen-devel] [PATCH 3/3] xen: eliminate scalability issues from initial mapping setup References: <1409834326-29287-1-git-send-email-jgross@suse.com> <1409834326-29287-4-git-send-email-jgross@suse.com> <54086244.7020601@citrix.com> <540862FE.7070108@citrix.com> In-Reply-To: <540862FE.7070108@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 04.09.14 at 15:02, wrote: > On 04/09/14 13:59, David Vrabel wrote: >> On 04/09/14 13:38, Juergen Gross wrote: >>> Direct Xen to place the initial P->M table outside of the initial >>> mapping, as otherwise the 1G (implementation) / 2G (theoretical) >>> restriction on the size of the initial mapping limits the amount >>> of memory a domain can be handed initially. >> The three level p2m limits memory to 512 GiB on x86-64 but this patch >> doesn't seem to address this limit and thus seems a bit useless to me. > > Any increase of the p2m beyond 3 levels will need to come with > substantial libxc changes first. 3 level p2ms are hard coded throughout > all the PV build and migrate code. No, there no such dependency - the kernel could use 4 levels at any time (sacrificing being able to get migrated), making sure it only exposes the 3 levels hanging off the fourth level (or not exposing this information at all) to external entities making this wrong assumption. Jan