From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36697) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cELHU-0004S1-1G for qemu-devel@nongnu.org; Tue, 06 Dec 2016 14:20:01 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cELHP-0006BE-Rp for qemu-devel@nongnu.org; Tue, 06 Dec 2016 14:20:00 -0500 Date: Tue, 6 Dec 2016 17:19:52 -0200 From: Eduardo Habkost Message-ID: <20161206191952.GD4027@thinpad.lan.raisama.net> References: <148104617887.7699.984921868108236415.stgit@bahia.lab.toulouse-stg.fr.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <148104617887.7699.984921868108236415.stgit@bahia.lab.toulouse-stg.fr.ibm.com> Subject: Re: [Qemu-devel] [PATCH] virtio: fix HW_COMPAT_2_6 macro for virtio-*-pci drivers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: qemu-devel@nongnu.org, Halil Pasic , "Michael S. Tsirkin" , qemu-stable@nongnu.org, Stefan Hajnoczi , Cornelia Huck , Paolo Bonzini 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. -- Eduardo