From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37139) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e35yl-0005IB-Sk for qemu-devel@nongnu.org; Fri, 13 Oct 2017 15:50:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e35yi-0008Co-10 for qemu-devel@nongnu.org; Fri, 13 Oct 2017 15:50:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50538) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e35yh-0008CY-Qa for qemu-devel@nongnu.org; Fri, 13 Oct 2017 15:50:39 -0400 References: <4cce2b8b-a411-bd5d-a06f-b0b80a5fb2f1@redhat.com> From: Laszlo Ersek Message-ID: Date: Fri, 13 Oct 2017 21:50:33 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] dynamic DRAM base for ArmVirtQemu List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Ard Biesheuvel , "Leif Lindholm (Linaro address)" , edk2-devel-01 , Drew Jones , qemu devel list , Igor Mammedov , Andrea Bolognani , libvirt devel 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