What were you trying to do that didn't work?

As subject

What is the impact of this issue to you?

Without this, it is inconvenient to resolve the error for the dependence of Hyper-V enlightenment

Please provide the package NVR for which the bug is seen:

libvirt v10.10.0-82-g247357cc29
qemu-kvm-9.1.0-7.el9.x86_64

How reproducible is this bug?:

100%

Steps to reproduce

1. Prepare a domain with <evmcs state='on'/>  only for hyperv
   XML:

<domain ...>
...
  <features>
    <acpi/>
    <apic/>
    <hyperv mode='custom'>
      <evmcs state='on'/>
    </hyperv>
    <smm state='on'/>
  </features>
...
</domain>

Create the domain:

➜  ~ virsh create win11.xml
error: Failed to create domain from win11.xml
error: internal error: QEMU unexpectedly closed the monitor (vm='win11'): 2024-12-30T06:49:12.221621Z qemu-kvm: Hyper-V enlightened VMCS (hv-evmcs) requires Hyper-V virtual APIC (hv-vapic)

It failed because of missing hv-vapic dependency

For the dependence of hyper-v features, see https://www.qemu.org/docs/master/system/i386/hyperv.html#existing-enlightenments

Expected results

expect libvirt could add hyper-v feature dependence automaticlly. For the example above, the domain could be created. Then hv-vapic  is added to the live XML:

<domain ...>
...
  <features>
    <acpi/>
    <apic/>
    <hyperv mode='custom'>
      <vapic state='on'/>
      <evmcs state='on'/>
    </hyperv>
    <smm state='on'/>
  </features>
...
</domain>

BTW, add a info log to the virtqemud log, like:

info: Add vapic to hyperv due to the dependence of evmcs

Actual results

As above