On Wed, 7 Dec 2016 11:59:17 -0200 Eduardo Habkost <ehabk...@redhat.com> 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 <ehabk...@redhat.com> 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 <gr...@kaod.org> > > > > > > > > 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
