From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752557Ab2G0LrU (ORCPT ); Fri, 27 Jul 2012 07:47:20 -0400 Received: from nat28.tlf.novell.com ([130.57.49.28]:46657 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752438Ab2G0LrS convert rfc822-to-8bit (ORCPT ); Fri, 27 Jul 2012 07:47:18 -0400 Message-Id: <50129C030200007800090F9B@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 12.0.0 Date: Fri, 27 Jul 2012 12:47:47 +0100 From: "Jan Beulich" To: "Stefano Stabellini" Cc: "xen-devel" , "Konrad Rzeszutek Wilk" , "linux-kernel@vger.kernel.org" Subject: Re: [Xen-devel] [PATCH 5/7] xen/p2m: Add logic to revector a P2M tree to use __va leafs. References: <1343335652-5659-1-git-send-email-konrad.wilk@oracle.com> <1343335652-5659-6-git-send-email-konrad.wilk@oracle.com> In-Reply-To: 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 27.07.12 at 13:18, Stefano Stabellini wrote: > On Thu, 26 Jul 2012, Konrad Rzeszutek Wilk wrote: >> 1) All P2M lookups instead of using the __ka address would >> use the __va address. This means we can safely erase from >> __ka space the PMD pointers that point to the PFNs for >> P2M array and be OK. >> 2). Allocate a new array, copy the existing P2M into it, >> revector the P2M tree to use that, and return the old >> P2M to the memory allocate. This has the advantage that >> it sets the stage for using XEN_ELF_NOTE_INIT_P2M >> feature. That feature allows us to set the exact virtual >> address space we want for the P2M - and allows us to >> boot as initial domain on large machines. >> >> So we pick option 2). > > 1) looks like a decent option that requires less code. > Is the problem with 1) that we might want to access the P2M before we > have __va addresses ready? AIUI 1) has no easy way of subsequently accommodating support for XEN_ELF_NOTE_INIT_P2M (where you almost definitely will want/need to reclaim the originally used VA space - if nothing else, then for forward compatibility with the rest of the kernel). Jan