From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34643) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cEdgX-0005NG-Ed for qemu-devel@nongnu.org; Wed, 07 Dec 2016 09:59:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cEdgS-0004UP-L7 for qemu-devel@nongnu.org; Wed, 07 Dec 2016 09:59:05 -0500 Received: from 4.mo68.mail-out.ovh.net ([46.105.59.63]:53731) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cEdgS-0004Tx-C0 for qemu-devel@nongnu.org; Wed, 07 Dec 2016 09:59:00 -0500 Received: from player763.ha.ovh.net (b9.ovh.net [213.186.33.59]) by mo68.mail-out.ovh.net (Postfix) with ESMTP id BFDF516E72 for ; Wed, 7 Dec 2016 15:58:58 +0100 (CET) Date: Wed, 7 Dec 2016 15:58:48 +0100 From: Greg Kurz Message-ID: <20161207155848.76429902@bahia> In-Reply-To: <20161207135917.GI4027@thinpad.lan.raisama.net> References: <148104617887.7699.984921868108236415.stgit@bahia.lab.toulouse-stg.fr.ibm.com> <20161206191952.GD4027@thinpad.lan.raisama.net> <20161206193159.GE4027@thinpad.lan.raisama.net> <20161207143925.7b3a54f2@bahia> <20161207135917.GI4027@thinpad.lan.raisama.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC for-2.8] machine: Convert abstract typename on compat_props to subclass names List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: qemu-devel@nongnu.org, Halil Pasic , "Michael S. Tsirkin" , qemu-stable@nongnu.org, Stefan Hajnoczi , Cornelia Huck , Paolo Bonzini On Wed, 7 Dec 2016 11:59:17 -0200 Eduardo Habkost wrote: > On Wed, Dec 07, 2016 at 02:39:25PM +0100, Greg Kurz wrote: > > On Tue, 6 Dec 2016 17:31:59 -0200 > > Eduardo Habkost wrote: > > > > > On Tue, Dec 06, 2016 at 05:19:52PM -0200, Eduardo Habkost wrote: > > > > On Tue, Dec 06, 2016 at 06:50:47PM +0100, Greg Kurz wrote: > > > > > Since commit "9a4c0e220d8a hw/virtio-pci: fix virtio behaviour", passing > > > > > -device virtio-blk-pci.disable-modern=off has no effect on 2.6 machine > > > > > types because the internal virtio-pci.disable-modern=on compat property > > > > > always prevail. > > > > > > > > > > This should ideally be fixed in the qdev properties core code, but it is > > > > > too late in the QEMU 2.8 schedule. So this patch fixes the issue by setting > > > > > the compat properties for every virtio-*-pci subtypes instead of the base > > > > > virtio-pci type. > > > > > > > > > > Signed-off-by: Greg Kurz > > > > > > > > So, it looks like the bug is present in many other cases... > > > > > > > > I have hacked QEMU to print a warning in case the driver name in > > > > compat_props refer to an abstract class or a class that have any > > > > subclasses. The results are below: > > > > > > > > apic-common.legacy-instance-id set for abstract class > > > > apic-common.vapic set for abstract class > > > > i386-cpu.arat set for abstract class > > > > i386-cpu.check set for abstract class > > > > i386-cpu.cpuid-0xb set for abstract class > > > > i386-cpu.fill-mtrr-mask set for abstract class > > > > i386-cpu.full-cpuid-auto-level set for abstract class > > > > i386-cpu.l3-cache set for abstract class > > > > i386-cpu.pmu set for abstract class > > > > pci-device.command_serr_enable set for abstract class > > > > pci-device.rombar set for abstract class > > > > pci-device.x-pcie-lnksta-dllla set for abstract class > > > > powerpc64-cpu.pre-2.8-migration set for abstract class > > > > s390-skeys.migration-enabled set for abstract class > > > > spapr-pci-host-bridge.ddw set for superclass > > > > spapr-pci-host-bridge.dynamic-reconfiguration set for superclass > > > > spapr-pci-host-bridge.mem64_win_size set for superclass > > > > spapr-pci-host-bridge.mem_win_size set for superclass > > > > spapr-pci-host-bridge.pre-2.8-migration set for superclass > > > > usb-device.full-path set for abstract class > > > > usb-device.msos-desc set for abstract class > > > > virtio-pci.disable-legacy set for abstract class > > > > virtio-pci.disable-modern set for abstract class > > > > virtio-pci.migrate-extra set for abstract class > > > > virtio-pci.page-per-vq set for abstract class > > > > virtio-pci.virtio-pci-bus-master-bug-migration set for abstract class > > > > virtio-pci.x-disable-pcie set for abstract class > > > > x86_64-cpu.arat set for abstract class > > > > x86_64-cpu.check set for abstract class > > > > x86_64-cpu.cpuid-0xb set for abstract class > > > > x86_64-cpu.fill-mtrr-mask set for abstract class > > > > x86_64-cpu.full-cpuid-auto-level set for abstract class > > > > x86_64-cpu.l3-cache set for abstract class > > > > x86_64-cpu.pmu set for abstract class > > > > > > > > I believe the cases where we are likely to cause real-world bugs > > > > are virtio-pci and the *-cpu classes (because -cpu is translated > > > > to -global). > > > > > > > > I'm not sure what should be the right fix in 2.8. I am > > > > considering a temporary hack to translate abstract class names in > > > > compat_props to global properties for all subclasses, in case > > > > they refer to an abstract class. This way we fix the bug where > > > > -global doesn't override compat_props properly, but keep the > > > > rules for -global untouched. > > > > > > What about this? > > > > > > > Indeed that would have been a clever workaround but it is too late anyway. :) > > > > BTW, that makes me think about Halil's comment in another mail, even if it > > is not strictly related to the comapt issue (but rather because I mentioned > > it in the changelog of my first patch): > > > > "So I can't even tell if -global virtio-pci.disable-modern=off is even legit > > on the command line." > > > > And indeed, -device doesn't accept abstract classes... shouldn't -global > > prohibit setting properties for them ? > > I'm not sure. Setting disable-modern for all virtio-pci devices > with a single -global option sounds very useful, for example. > Indeed but, unless I've missed something *again*, you cannot know about it without reading the code... maybe this calls for a '-global help' option to list them all ? > Also, if we start rejecting it we risk breaking existing > configurations. We would need to deprecate it first (making it > print a warning) and reject it a few releases later. > This would be an undocumented configuration but I get your point, so it's probably better to keep it... especially if it's useful :) Cheers. -- Greg