Re: [Qemu-discuss] guest and host CPU are not compatible

[Jakob Bohm]

On 18/05/2017 13:17, Mah shid wrote:
> i am new to work with qemu. i wanted to migrate a vm to another host with
> virsh :
> virsh migrate --live --copy-storage-all test3  qemu+ssh://
> address@hidden/system --verbose
> and virt manager. i got this error with both of them:
>
> unsupported configuration: guest and host CPU are not compatible: Host CPU
> does not provide required features: fma, x2apic, movbe, tsc-deadline,
> xsave, avx, fsgsbase, bmi1, avx2, smep, bmi2, erms, invpcid, rdseed, adx,
> smap, 3dnowprefetch
>
> i couldnt find any solution
Seems obvious:  The new host computer you are migrating to has a
different physical (maybe older) CPU model than the old host.  The
virtual machine is using hardware virtualization (kvm, xen or
similar).  And the virtual machine was configured to provide the
running code access to those CPU features listed in the error message.

Qemu on the new host computer cannot emulate those missing features.
And programs (including operating systems) running in the virtual
machine cannot be told that they are suddenly running on a different
CPU with less capabilities.

If you really want the ability to migrate the VM between those two
host machines, you will have to configure the virtual machine to have
a virtual CPU that can be emulated by both machines, typically a CPU
at least as old as the oldest of the host CPUs.  Then qemu may be able
to hide the extra features from the VM when the VM is running on the
newer CPU, thus allowing the VM to safely migrate between those hosts
without an "unreal" sudden change in CPU features.

Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
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