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Re: [Qemu-devel] [PATCH for-2.8.1 v2] machine: Convert abstract typename


From: Halil Pasic
Subject: Re: [Qemu-devel] [PATCH for-2.8.1 v2] machine: Convert abstract typename on compat_props to subclass names
Date: Tue, 13 Dec 2016 13:17:45 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1


On 12/12/2016 09:49 PM, Eduardo Habkost wrote:
> Original problem description by Greg Kurz:
> 
>> 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.
> The same bug also affects other abstract type names mentioned on
> compat_props by machine-types: apic-common, i386-cpu, pci-device,
> powerpc64-cpu, s390-skeys, spapr-pci-host-bridge, usb-device,
> virtio-pci, x86_64-cpu.
> 
> The right fix for this problem is to make sure compat_props and
> -global options are always applied in the order they are
> registered, instead of reordering them based on the type
> hierarchy. But changing the ordering rules of -global is risky
> and might break existing configurations, so we shouldn't do that
> on a stable branch.
> 
> This is a temporary hack that will work around the bug when
> registering compat_props properties: if we find an abstract class
> on compat_props, register properties for all its non-abstract
> subtypes instead. This will make sure -global won't be overridden
> by compat_props, while keeping the existing ordering rules on
> -global options.
> 
> Note that there's one case that won't be fixed by this hack:
> "-global spapr-pci-vfio-host-bridge.<option>=<value>" won't be
> able to override compat_props, because spapr-pci-host-bridge is
> not an abstract class.
> 
> Signed-off-by: Eduardo Habkost <address@hidden>
> ---

Reviewed-by: Halil Pasic <address@hidden>




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