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ndemou
Asked: 2018-07-02 11:11:46 +0800 CST

KVM/libvirt: how to migrate between 2 hosts with different CPUs

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I tried to migrate my KVM host from a host with AMD cpu to a host with Intel CPU but when I run virsh start guest_name I got error: unsupported configuration: CPU model ... is not supported by hypervisor.

I know that KVM supports such a migration (in the FAQ they even talk about live migration between 64 bit AMD/Intel CPUs). What should I do?

kvm-virtualization

1 Answers

  1. Best Answer

    You should edit the part of the xml definition of your guest so that it contains a subset of CPU capabilities that are found in both CPUs (Intel and AMD). You can use virsh to find this subset. Here's how:

    At the 1st host

    $ virsh capabilities | virsh cpu-baseline /dev/stdin > /tmp/host1.xml

# copy this file to Host#2 -- e.g.:
$ scp /tmp/host1.xml $HOST2:/tmp/host1.xml

    Everything else happens at the 2nd host

    $ virsh capabilities | virsh cpu-baseline /dev/stdin > /tmp/host2.xml
$ cat /tmp/host1.xml /tmp/host2.xml > /tmp/both-cpus.xml

    Now edit both-cpus.xml and:

    1. keep only the <cpu>....</cpu> sections
    2. from these sections remove the lines with <vendor>....</vendor>

    Finally run this:

    $ virsh cpu-baseline /tmp/both-cpus.xml

    If you get this error "XML error: Missing CPU architecture" add <arch>x86_64</arch> in both <cpu>...</cpu> sections. Ofcourse x86_64 is for modern AMD and Intel CPUs, if you work with some other architecture adjust appropriately (thanks to harald for this tip).

    The output of the above command must be used inside the xml definitions of the guest.

    References

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