From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754054Ab3F0SdT (ORCPT ); Thu, 27 Jun 2013 14:33:19 -0400 Received: from mga01.intel.com ([192.55.52.88]:13504 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753671Ab3F0SdR (ORCPT ); Thu, 27 Jun 2013 14:33:17 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,954,1363158000"; d="scan'208";a="356803272" Message-ID: <51CC8551.1090202@linux.intel.com> Date: Thu, 27 Jun 2013 11:32:49 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: James Bottomley CC: Matt Fleming , Leif Lindholm , Grant Likely , Stephen Warren , "linux-arm-kernel@lists.infradead.org" , linux-efi@vger.kernel.org, "linux-doc@vger.kernel.org" , Linux Kernel Mailing List , "patches@linaro.org" , Thomas Gleixner , matt.fleming@intel.com Subject: Re: [PATCH 1/4] Documentation: arm: [U]EFI runtime services References: <1372183863-11333-1-git-send-email-leif.lindholm@linaro.org> <1372183863-11333-2-git-send-email-leif.lindholm@linaro.org> <51CA2B03.4080106@wwwdotorg.org> <20130626135311.GA9078@rocoto.smurfnet.nu> <20130626135933.GQ22026@console-pimps.org> <1372257499.2168.5.camel@dabdike> In-Reply-To: <1372257499.2168.5.camel@dabdike> 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 On 06/26/2013 07:38 AM, James Bottomley wrote: > On Wed, 2013-06-26 at 14:59 +0100, Matt Fleming wrote: >> On Wed, 26 Jun, at 03:53:11PM, Leif Lindholm wrote: >>> It's completely feasible, but we'd need to use a different method to do >>> the boot services call with a 1:1 mapping (idmap support is not available >>> until much later in the boot process). >> >> At least if you no longer relied upon the idmap we could potentially >> have a single efi_enter_virtual_mode() call-site in init/main.c, which >> would be nice. > > The fixed virtual address scheme currently being looked at for x86_64 to > make SetVirtualAddressMap() kexec invariant doesn't work on 32 bit > because the address space isn't big enough. For ARM, given that we've > much more opportunity to work with the vendors, can we just avoid > transitioning to a virtual address map and always just install a > physical mapping before doing efi calls? > What we could do on x86-32 is to map from 0xc0000000 downwards. It wouldn't be invariant across kernel builds with different user/kernel split... but I'm not sure we can win that one. The other option is to say sod it and just use straight 1:1 mapping on 32 bits... -hpa