[SOLVED] How to add flags in libvirt?

ddenial · 11-15-2017, 08:42 AM

Hello

I am following this guide to install Windows 7 guest OS with virtio drivers.

https://access.redhat.com/articles/2470791

Even though I installed Windows Guest Machine successfully, I don't know how to add flags as mentioned in this tutorial.

The tutorial says:

Quote:

The following flags should be set with libvirt to make sure the Windows guest virtual machine works efficiently:

hv_relaxed
hv_spinlocks=0x1fff
hv_vapic
hv_time

But how and where to add them? I really appreciate any help.

Thank you.

AwesomeMachine · 11-16-2017, 03:28 AM

Try editing:

Code:

nova/virt/libvirt/config.py

ddenial · 11-17-2017, 07:43 AM

Quote:

Originally Posted by AwesomeMachine

Try editing:

Code:

nova/virt/libvirt/config.py

Thanks, but I using KVM on CentOS 7.4 host. So I don't have nova/virt/libvirt/config.py file.

After some deep search, I came across this Redhat Bug Report page, and it turns out that the flags are set by default for Windows VM.

The recommended qemu configuration is:

Code:

 -cpu ...,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time

Which maps to the libvirt XML:

   <features>
     <hyperv>
       <relaxed state='on'/>
       <vapic state='on'/>
       <spinlocks state='on' retries='8191'/>
     </hyperv>
   <features/>

   <clock ...>
     <timer name='hypervclock' present='yes'/>
   </clock>

Proof: After running Windows Virtual Machine, I ran this command in CentOS host:

Code:

# ps -aux | grep qemu | grep -Eo 'hv_relaxed|hv_spinlocks=0x1fff|hv_vapic|hv_time'
hv_time
hv_relaxed
hv_vapic
hv_spinlocks=0x1fff

I also came across this good article on how to install Windows with Passthrough. So anybody interested can visit Running Windows 10 on Linux using KVM with VGA Passthrough

Thankyou.