From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37826) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WBYnF-0001pw-Fa for qemu-devel@nongnu.org; Thu, 06 Feb 2014 18:55:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WBYn5-00077H-Ji for qemu-devel@nongnu.org; Thu, 06 Feb 2014 18:55:41 -0500 Received: from mail-qc0-x22c.google.com ([2607:f8b0:400d:c01::22c]:38263) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WBYn4-00075y-K2 for qemu-devel@nongnu.org; Thu, 06 Feb 2014 18:55:31 -0500 Received: by mail-qc0-f172.google.com with SMTP id c9so4552167qcz.17 for ; Thu, 06 Feb 2014 15:55:29 -0800 (PST) Sender: Paolo Bonzini Message-ID: <52F420EA.9000008@redhat.com> Date: Fri, 07 Feb 2014 00:55:22 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <52F347C3.9030600@msgid.tls.msk.ru> <1391676619.17309.39.camel@nilsson.home.kraxel.org> <52F38939.8010704@msgid.tls.msk.ru> <1391692554.25128.7.camel@kazak.uk.xensource.com> <52F38E65.4010003@msgid.tls.msk.ru> <1391694723.25128.14.camel@kazak.uk.xensource.com> <1391697093.17309.48.camel@nilsson.home.kraxel.org> <1391698125.25128.49.camel@kazak.uk.xensource.com> In-Reply-To: <1391698125.25128.49.camel@kazak.uk.xensource.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] 128Kb bios size and older machines? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Ian Campbell , Gerd Hoffmann Cc: Michael Tokarev , qemu-devel Il 06/02/2014 15:48, Ian Campbell ha scritto: >>> > > I'm not sure why the BIOS size is relevant to migration anyway, Xen >>> > > doesn't load a new BIOS on the target host, the BIOS image is part of >>> > > the migrated RAM. >> > >> > The memory layout is different with a larger bios as qemu makes the >> > virtual flash as big as the bios image is. The different memory layout >> > in turn makes live migration fail. > OK. Xen doesn't emulate flash so it doesn't have this issue. It's problematic even without flash. At least in Xen, all ROM memory blocks are migrated, not just the main RAM. Migration of RAM/ROM block data is independent from where the RAM/ROM is mapped in guest physical address space. In the guest, a 128k BIOS is at fffe0000-ffffffff. A 256k BIOS is at fffc0000-ffffffff. If the destination prepares the memory map for a 256k BIOS, and the source sends the data for a 128k BIOS, the 128k BIOS is erroneously placed at ffffc0000-fffdffff. There is no reset vector fffffff0. The guest works fine until you reboot it, then it breaks. Paolo