From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758199Ab2IGIC2 (ORCPT ); Fri, 7 Sep 2012 04:02:28 -0400 Received: from mga09.intel.com ([134.134.136.24]:53574 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756189Ab2IGICY (ORCPT ); Fri, 7 Sep 2012 04:02:24 -0400 Subject: Re: [PATCH] x86, efi: 1:1 pagetable mapping for virtual EFI calls From: Matt Fleming To: Jan Beulich Cc: "H. Peter Anvin" , Vasco Dias , Matthew Garrett , linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, cJ-ko@zougloub.eu In-Reply-To: <5049C12B020000780009998C@nat28.tlf.novell.com> References: <1346937309-1581-1-git-send-email-matt@console-pimps.org> <5048D09A020000780009965B@nat28.tlf.novell.com> <1346946465.4244.107.camel@mfleming-mobl1.ger.corp.intel.com> <5048D83D.8000408@zytor.com> <5049C12B020000780009998C@nat28.tlf.novell.com> Content-Type: text/plain; charset="UTF-8" Organization: Intel Corporation (UK) Ltd. - Registered No. 1134945 - Pipers Way, Swindon SN3 1RJ Date: Fri, 07 Sep 2012 09:02:11 +0100 Message-ID: <1347004931.4244.112.camel@mfleming-mobl1.ger.corp.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-09-07 at 08:40 +0100, Jan Beulich wrote: > >>> On 06.09.12 at 19:07, "H. Peter Anvin" wrote: > > Anyone care to refresh my memory why we can't use the "global" > > 1:1+kernel map, possibly with some improvements (which would benefit the > > users of those maps too)? With that I mean initial_page_map on i386 and > > trampoline_pgd on x86-64... > > I don't think you want anything inserted in the low part of those > (kernel-only) page tables, not even transiently. There are already things inserted into the low part of those page tables. In fact, the main purpose is to provide a 1:1 mapping for realmode code. See machine_real_restart(). I think there's definitely merit to the approach Peter outlined above. There's a variety of places in arch/x86 where a 1:1 mapping is needed. It would be good to have a single pagetable that provides this.