From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49721) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WzJ4k-0004l2-4X for qemu-devel@nongnu.org; Tue, 24 Jun 2014 01:15:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WzJ4a-00086d-SG for qemu-devel@nongnu.org; Tue, 24 Jun 2014 01:15:22 -0400 Received: from mail-we0-x231.google.com ([2a00:1450:400c:c03::231]:38374) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WzJ4a-00086U-Md for qemu-devel@nongnu.org; Tue, 24 Jun 2014 01:15:12 -0400 Received: by mail-we0-f177.google.com with SMTP id u56so7970123wes.22 for ; Mon, 23 Jun 2014 22:15:11 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <53A9095B.3070803@redhat.com> Date: Tue, 24 Jun 2014 07:15:07 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <53A8366B.1020301@ozlabs.ru> <53A840C8.8060607@redhat.com> <53A89D98.3030708@ozlabs.ru> In-Reply-To: <53A89D98.3030708@ozlabs.ru> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] machines and versions - why so many? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexey Kardashevskiy , "qemu-devel@nongnu.org" Cc: Paul Mackerras , =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= , Alexander Graf Il 23/06/2014 23:35, Alexey Kardashevskiy ha scritto: > nec-usb-xhci is off for PC_COMPAT_1_3 because of what? PIIX emulation was > broken in 1.3? Or nec-usb-xhci? nec-usb-xhci is not "off". .driver = "nec-usb-xhci",\ .property = "msi",\ .value = "off",\ What's off is MSI (and MSI-X), because it wasn't implemented. > If it is the latter, why is the tweak limited by PC? Because at the time nobody cared about migration compatibility (even now only pSeries is starting to care). > Looks like I must copy PC_COMPAT_X_X as PSERIES_COMPAT_X_X starting 1.6 (or > 1.7 - whichever starts supporting migration well enough on pseries) because > pretty much of what they do is tweaking PCI devices and we can have all of > these devices on pseries. It's not necessary to do this retroactively, unless you're planning to test forward migration from 1.6 to 2.1. Just start with 2.2 (and add pseries-2.1 now as an alias). Note that firmware interfaces and CPU features should also be versioned if they're guest visible. That's the point of functions like pc_compat_1_6. > And then keep an eye on what is happening in PC > world to copy same tweaks to pseries as they come. Is that correct? Yes. We should come up sooner or later with a way to share the tweaks though. > Others (ARM, s390) do not do that because they do not support PCI? Or > migration? Or some other reason? This is not limited to PCI. Others do not support migration across different QEMU versions. Paolo