Command line equivalent for cpu pinning

[Gianluca Cecchi <gianluca.cecchi@xxxxxxxxx>]

Hello,

on my Fedora 39 with 

libvirt 9.7.0-3.fc39

qemu-kvm 8.1.3-5.fc39

kernel 6.8.11-200.fc39.x86_64

I'm testing cpu pinning

The hw is a Nuc with

13th Gen Intel(R) Core(TM) i7-1360P

If I pass from this in my guest xml:

  <vcpu placement='static'>4</vcpu>
  <cpu mode='host-passthrough' check='none' migratable='on'>
    <topology sockets='1' dies='1' cores='4' threads='1'/>
  </cpu>

to this:

  <vcpu placement='static'>4</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='0'/>
    <vcpupin vcpu='1' cpuset='2'/>
    <vcpupin vcpu='2' cpuset='4'/>
    <vcpupin vcpu='3' cpuset='6'/>
  </cputune>
  <cpu mode='host-passthrough' check='none' migratable='on'>
    <topology sockets='1' dies='1' cores='4' threads='1'/>
  </cpu>

It seems to me that the generated command line of the qemu-system-x88_64 process doesn't change.

As if the cputune options were not considered

What should I see as different?

Actually it seems it is indeed honored, because if I run stress-ng in the VM in the second scenario and top command in the host, I see only pcpu 0,2,4,6 going up with the load.

Instead the first scenario keeps several different cpus alternating in the load.

The real question could be: if I want to reproduce from the command line the cputune options, how can I do it?

Is it only a cpuset wrapper used for the qemu-system-x86_64 process to place it in a cpuset control group?

I see for the pid of the process

$ sudo cat /proc/340215/cgroup
0::/machine.slice/machine-qemu\x2d8\x2dc7anstgt.scope/libvirt/emulator

and

$ sudo systemd-cgls /machine.slice
CGroup /machine.slice:
└─machine-qemu\x2d8\x2dc7anstgt.scope …
  └─libvirt
    ├─340215 /usr/bin/qemu-system-x86_64....

    ├─vcpu1
    ├─vcpu2
    ├─vcpu0
    ├─emulator
    └─vcpu3

What could be an easy command to replicate from the command line what virsh does?

Thanks in advance

Gianluca