While I understand the concern, using the 'host-model' should solve the migration issue. I currently have a Intel Xeon E5-2620 v4 (32) KVM host and my VMs shows as Intel (Broadwell, IBRS). A massive difference, but migrations work fine and VM performance drop is not that noticeable. You could change back to host-passthrough once the migration is completed.

On 5/16/23 17:03, Gary Dixon wrote:

We have tried host-model – however virsh capabilities on the newer servers doesn’t even pick up the correct cpu map xml definition – the actual CPU is a AMD EPYC 7763 (codename Milan) and libvirt thinks it’s a ‘Rome’ cpu – a whole generation earlier !!!

Gary Dixon​
Senior Technical Consultant
T:  +44 161 537 4990
E: *v* <tel:+44%207989717661>ms@quadris‑support.com
W: www.quadris.co.uk

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*From:*Granwille Strauss <granwi...@namhost.com.INVALID>
*Sent:* Tuesday, May 16, 2023 3:51 PM
*To:* users@cloudstack.apache.org
*Cc:* gary.di...@quadris.co.uk.INVALID
*Subject:* Re: preventing VM Live migration between Pods

Hi Gary

I am still fairly new to ACS myself, but as far as I can recall, using the 'host-passthrough' option is prone to cause problems during migrations, this is also mentioned in the documentation: https://docs.cloudstack.apache.org/en/latest/installguide/hypervisor/kvm.html?highlight=host-passthrough#configure-cpu-model-for-kvm-guest-optional I suggest changing to 'host-model' instead:

    *host-passthrough* may lead to migration failure,if you have this
    problem, you should use host-model or custom. guest.cpu.features
    will force cpu features as a required policy so make sure to put
    only those features that are provided by the host CPU. As your kvm
    cluster needs to be made up of homogenous nodes anyway (see System
    Requirements), it might make most sense to use
    guest.cpu.mode=host-model or guest.cpu.mode=host-passthrough

On 5/16/23 15:13, Gary Dixon wrote:

    Hi everyone

    Other than disabling a Pod – is there a way to prevent live
    migration of VM’s between Pods in ACS ?

    We are on version 4.15.2 with Ubuntu 20.04 KVM hosts.  Each Pod
    contains a single cluster of Homogenous hosts – however there are
    only slight differences between the CPU’s on the physical hosts in
    each Cluster. We have the guest.cpu.mode set to host-passthrough
    but have noticed serious issues when a VM is live migrated between
    specific Pods (usually if a VM is started on a cluster with the
    slightly better CPU’s and then live migrated to an older Pod)

    We have tried setting the guest.cpu.mode to host-passthrough with
    specific CPU features using the “guest.cpu.features=” and then
    setting all of the host’s CPU flags shown from the output of the
    lscpu command in a space separated list as instructed from ACS
    documentation – but we then are unable to even start a VM –
    insufficient resources error, - if we remove the
    guest.cpu.features from the agent.properties – then we can start a
    VM again.

    It would be good if we had an option or a setting to just not
    allow live migration of VM’s between pods and therefore can only
    perform a ‘cold’ migration if we wish to move a VM to another Pod.

    Any thoughts on this ?

    BR

    Gary


    *Gary Dixon**​***

    Senior Technical Consultant

    T:  +44 161 537 4990

    E: *v* <tel:+44%207989717661>ms@quadris‑support.com

    W: www.quadris.co.uk <http://www.quadris.co.uk>

    *The information contained in this e-mail from Quadris may be
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