Greetings,

passthrough means you pass the device as is with minimal or no change at all.
for example, if you passthrough a pci device, the pci address might change but the rest won't.
 
hope this helps
 
Dagg
 
Sent: Sunday, November 14, 2021 at 11:52 PM
From: "Toolybird" <toolybird@tuta.io>
To: "Libvirt Users" <libvirt-users@redhat.com>
Subject: CPU vendor_id handling
Hello,
 
There are times when spoofing the CPU vendor_id is convenient. For example, some x86 guest OS's only run on Intel and refuse to run on an AMD host. Libvirt does support this in the "host-model" case, but it doesn't work for CPU "host-passthrough". On the QEMU command line it's as easy as:
 
$ qemu-system-x86_64 -cpu host,vendor=GenuineIntel
 
This works fine in libvirt XML:
 
<cpu mode='host-model'>
  <model vendor_id='GenuineIntel'/>
</cpu>
 
This doesn't:
 
<cpu mode='host-passthrough'>
  <model vendor_id='GenuineIntel'/>
</cpu>
 
Libvirt silently strips out the model line after saving "virsh edit ..."
 
Is there any reason why libvirt cannot support this in the host-passthrough case? The status quo means that some folks end up resorting to <qemu:arg value='-cpu'/> hacks which of course causes all sorts of confusion with multiple -cpu lines getting passed to QEMU.
 
Thanks