Re: Expose support for HyperV features via QMP

[manish.mishra]

On 09/02/23 7:47 pm, Vitaly Kuznetsov wrote:
> Alex Bennée <alex.bennee@linaro.org> writes:
>
> > "manish.mishra" <manish.mishra@nutanix.com> writes:
> >
> > > Hi Everyone,
> > >
> > > Checking if there is any feedback on this.
> > I've expanded the CC list to some relevant maintainers and people who
> > have touched that code in case this was missed.
> >
> > > Thanks
> > >
> > > Manish Mishra
> > >
> > > On 31/01/23 8:17 pm, manish.mishra wrote:
> > >
> > >   Hi Everyone,
> > >   I hope everyone is doing great. We wanted to check why we do not expose 
> > > support for HyperV features in
> > >   Qemu similar to what we do for normal CPU features via query-cpu-defs or 
> > > cpu-model-expansion QMP
> > >   commands. This support is required for live migration with HyperV features as 
> > > hyperv passthrough is not
> > >   an option. If users had knowledge of what features are supported by source 
> > > and destination, VM can be
> > >   started with an intersection of features supported by both source and 
> > > destination.
> > >   If there is no specific reason for not doing this, does it make sense to add 
> > > a new QMP which expose
> > >   support (internally also validating with KVM or KVM_GET_SUPPORTED_HV_CPUID 
> > > ioctl) for HyperV
> > >   features.
> > >   Apologies in advance if i misunderstood something.
> Thanks for Ccing me.
>
> Hyper-V features should appear in QMP since
>
> commit 071ce4b03becf9e2df6b758fde9609be8ddf56f1
> Author: Vitaly Kuznetsov <vkuznets@redhat.com>
> Date:   Tue Jun 8 14:08:13 2021 +0200
>
>      i386: expand Hyper-V features during CPU feature expansion time
>
> also, the support for Hypre-V feature discovery was just added to
> libvirt:
>
> 903ea9370d qemu_capabilities: Report Hyper-V Enlightenments in domcapabilities
> 10f4784864 qemu_capabilities: Query for Hyper-V Enlightenments
> ff8731680b qemuMonitorJSONGetCPUModelExpansion: Introduce @hv_passthrough 
> argument
> 7c12eb2397 qemuMonitorJSONMakeCPUModel: Introduce @hv_passthrough argument
> 7c1ecfd512 domain_capabilities: Expose Hyper-V Enlightenments
> 179e45d237 virDomainCapsEnumFormat: Retrun void
> a7789d9324 virDomainCapsEnumFormat: Switch to virXMLFormatElement()
>
> in case this is not enough, could you please elaborate on the use-case
> you have in mind?

Thanks Vitaly, Alex,

Yes this should work. Sorry I checked qemu master code but not sure how i 
missed this :).

Thanks

Manish Mishra