From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=lersek@redhat.com; receiver=edk2-devel@lists.01.org Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 23E6F202E59CA for ; Fri, 13 Oct 2017 12:47:07 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 90A3691EA3; Fri, 13 Oct 2017 19:50:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 90A3691EA3 Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=lersek@redhat.com Received: from lacos-laptop-7.usersys.redhat.com (ovpn-123-190.rdu2.redhat.com [10.10.123.190]) by smtp.corp.redhat.com (Postfix) with ESMTP id C535B5C543; Fri, 13 Oct 2017 19:50:35 +0000 (UTC) To: Peter Maydell Cc: Ard Biesheuvel , "Leif Lindholm (Linaro address)" , edk2-devel-01 , Drew Jones , qemu devel list , Igor Mammedov , Andrea Bolognani , libvirt devel References: <4cce2b8b-a411-bd5d-a06f-b0b80a5fb2f1@redhat.com> From: Laszlo Ersek Message-ID: Date: Fri, 13 Oct 2017 21:50:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 13 Oct 2017 19:50:38 +0000 (UTC) Subject: Re: dynamic DRAM base for ArmVirtQemu X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 Oct 2017 19:47:07 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 10/13/17 18:18, Peter Maydell wrote: > On 13 October 2017 at 13:51, Laszlo Ersek wrote: >> Another idea is to move *the* system DRAM base to a different guest-phys >> address. (Likely using a different version of the "virt" machine type, >> or even a different machine type entirely.) This would not be compatible >> with current ArmVirtQemu, which hard-codes the system DRAM base in >> several, quite brittle / sensitive, locations. (More on this later -- >> that's going to be the larger part of my email anyway.) In order to >> handle the new base in ArmVirtQemu, two approaches are possible: change >> the hard-coded address(es), or cope with the address dynamically. > > I strongly don't want to move the DRAM base in the "virt" board. You really cannot *not* want it more strongly than I :) (See my answer to Ard for why I went to such lengths nonetheless in mapping out the consequences for the firmware -- I knew and feared I'd find monsters there, but when I'm invited to look, it's only honest to look.) > This is one of the few fixed things we've said that guest code > can rely on without having to fish the information out of the > device tree. And, as one co-maintainer of one guest firmware, I'm immensely relieved to learn about, and benefit from, this guarantee. Thanks, Laszlo