> Out of curiosity, I got 2 questions:
Hi
> 1. Where does the domcapabilities are being retrieved from?
You can get it by running 'virsh domcapabilities', it has some
parameters that can change the output, look for domcapabilities
in 'man virsh'.
To extend the answer, the data are provided by libvirt and libvirt
gets the data from QEMU (libvirt >= 3.2.0 and QEMU >= 2.9.0) or from
it's own database and cpuid.
Ok.
> 2. Is is possible to change some flags (in the CPU section) from 'require'
> to disable and vice versa? (i'm talking system wide, not per VM) if so, how?
No, these domcapabilities returns what is possible with specific QEMU
on specific host. If you want to disable some features or enable them
you need to specify that for every singe VM.
My question is why would you like to change the CPU features?
I'm tracking an issue with AMD's Zen/Zen+ based processors.
The "monitor" CPU flag is not being exposed in nested virtualization in the guest OS. I tried it with Hyper-V, ESXi, and XenServer as well as KVM.
With Libvirt - it is, indeed, being disabled and this behavior is correct:
virsh domcapabilities | grep monitor
<feature policy='disable' name='monitor'/>
<feature policy='disable' name='monitor'/>
However, when trying to use oVirt in nested virtualization with any AMD Zen/Zen+ based CPU, it doesn't let create or run any VM and it complains about "monitor" is missing, and I'm trying to figure out who needs to fix the code, either oVirt or the KVM devs. That's why I wanted to see if it's an error or not.
Thanks,
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