[CentOS-virt] Live Migration and LibVirt CPU Mode

Dear Oisin,
I would recommend you do the offline migration(Export/Import) instead due
to CPU spec are different, refer link--> "
https://bugs.launchpad.net/nova/+bug/1082414" and "
https://review.openstack.org/#/c/161944/2". This save a lot more time
instead of bug digging.

Hope that helps.
Xlord

On Thu, Jul 6, 2017 at 9:29 AM, Oisin O'Malley <oisin.omalley at iocane.com.au>
wrote:

> Hi All,
>
> First time mailing here, I hope someone can help. We’re running a
> OpenStack Newton environment on top of CentOS-7.3, LibVirt and Qemu-KVM-EV.
> We are encountered an issue live migrating a VM between 2 hosts with
> different CPUs and LibVirt throws the following error:
>
> libvirtError: unsupported configuration: guest and host CPU are not
> compatible: Host CPU does not provide required features: fma, x2apic,
> movbe, tsc-deadline, xsave, osxsave, avx, f16c, rdrand, fsgsbase,
> tsc_adjust, bmi1, hle, avx2, smep, bmi2, erms, invpcid, rtm, rdseed, adx,
> smap, xsaveopt, abm, 3dnowprefetch; try using 'Broadwell-noTSX' CPU model.
>
>
> LibVirt appears to be comparing the source and destination host CPUs,
> instead of guest VM and destination host CPUs. The VM is configured with a
> common set CPU features that are compatible with both (see below) and can
> run on both hosts without issue. The hosts have Westmere and Broadwell CPUs
> (See host CPU capabilities below). The VM can be booted on the Westmere
> host, successfully live migrated to the Broadwell host, but then throws the
> above error when we attempt to live migrating back to the Westmere host.
>
> Due to how our Westmere hosts were configured in OpenStack Nova, the VMs
> CPU is configured with "cpu mode='host-model'", which fail to migrate. BUT
> if the VMs CPU is configured with "cpu mode='custom' match='exact'" it can
> be successfully migrate both ways. It appears that when a VMs CPU is
> configured with "cpu mode='host-model'" the guests CPU is ignored and the
> host CPUs are compared instead. Which I believe is incorrect behaviour, is
> this a known issue and/or have any workarounds.
>
> The VMs will be configure to use "cpu mode='custom'" with a Westmere model
> on their next reboot, but rebooting all VMs prior to migration is something
> we really want to avoid.
>
> There has already been some discussion on this issue on the OpenStack
> mailing list: http://lists.openstack.org/pipermail/openstack/2017-July/
> thread.html#45139
>
> The following package versions are being used;
> libvirt-daemon-kvm.x86_642.0.0-10.el7_3.4
> qemu-kvm-ev.x86_6410:2.6.0-28.el7_3.3.1
> kernel.x86_643.10.0-514.16.1.el7
>
>
> The Qemu-KVM processes CPU parameters of the running VMs;
>
> -cpu Westmere,+vme,+ds,+acpi,+ss,+ht,+tm,+pbe,+pclmuldq,+dtes64,
> +monitor,+ds_cpl,+vmx,+smx,+est,+tm2,+xtpr,+pdcm,+pcid,+
> dca,+arat,+pdpe1gb,+rdtscp
>
>
> Guest CPU Configuration that fails to migrate;
>
> <cpu mode='host-model'>
>     <model fallback='allow'>Westmere</model>
>     <vendor>Intel</vendor>
>     <topology sockets='1' cores='1' threads='1'/>
>     <feature policy='require' name='vme'/>
>     <feature policy='require' name='ds'/>
>     <feature policy='require' name='acpi'/>
>     <feature policy='require' name='ss'/>
>     <feature policy='require' name='ht'/>
>     <feature policy='require' name='tm'/>
>     <feature policy='require' name='pbe'/>
>     <feature policy='require' name='pclmuldq'/>
>     <feature policy='require' name='dtes64'/>
>     <feature policy='require' name='monitor'/>
>     <feature policy='require' name='ds_cpl'/>
>     <feature policy='require' name='vmx'/>
>     <feature policy='require' name='smx'/>
>     <feature policy='require' name='est'/>
>     <feature policy='require' name='tm2'/>
>     <feature policy='require' name='xtpr'/>
>     <feature policy='require' name='pdcm'/>
>     <feature policy='require' name='pcid'/>
>     <feature policy='require' name='dca'/>
>     <feature policy='require' name='arat'/>
>     <feature policy='require' name='pdpe1gb'/>
>     <feature policy='require' name='rdtscp'/>
>   </cpu>
>
>
> Guest CPU Configuration that successfully migrates;
>
>   <cpu mode='custom' match='exact'>
>     <model fallback='allow'>Westmere</model>
>     <topology sockets='1' cores='1' threads='1'/>
>   </cpu>
>
>
> Westmere Hosts CPU capabilities;
>
> <cpu>
>       <arch>x86_64</arch>
>       <model>Westmere</model>
>       <vendor>Intel</vendor>
>       <topology sockets='1' cores='4' threads='2'/>
>       <feature name='vme'/>
>       <feature name='ds'/>
>       <feature name='acpi'/>
>       <feature name='ss'/>
>       <feature name='ht'/>
>       <feature name='tm'/>
>       <feature name='pbe'/>
>       <feature name='pclmuldq'/>
>       <feature name='dtes64'/>
>       <feature name='monitor'/>
>       <feature name='ds_cpl'/>
>       <feature name='vmx'/>
>       <feature name='smx'/>
>       <feature name='est'/>
>       <feature name='tm2'/>
>       <feature name='xtpr'/>
>       <feature name='pdcm'/>
>       <feature name='pcid'/>
>       <feature name='dca'/>
>       <feature name='arat'/>
>       <feature name='pdpe1gb'/>
>       <feature name='rdtscp'/>
>       <feature name='invtsc'/>
>       <pages unit='KiB' size='4'/>
>       <pages unit='KiB' size='2048'/>
>       <pages unit='KiB' size=
>
>
> Broadwell Host CPU Capabilities;
>
>     <cpu>
>       <arch>x86_64</arch>
>       <model>Broadwell</model>
>       <vendor>Intel</vendor>
>       <topology sockets='1' cores='12' threads='2'/>
>       <feature name='vme'/>
>       <feature name='ds'/>
>       <feature name='acpi'/>
>       <feature name='ss'/>
>       <feature name='ht'/>
>       <feature name='tm'/>
>       <feature name='pbe'/>
>       <feature name='dtes64'/>
>       <feature name='monitor'/>
>       <feature name='ds_cpl'/>
>       <feature name='vmx'/>
>       <feature name='smx'/>
>       <feature name='est'/>
>       <feature name='tm2'/>
>       <feature name='xtpr'/>
>       <feature name='pdcm'/>
>       <feature name='dca'/>
>       <feature name='osxsave'/>
>       <feature name='f16c'/>
>       <feature name='rdrand'/>
>       <feature name='arat'/>
>       <feature name='tsc_adjust'/>
>       <feature name='cmt'/>
>       <feature name='xsaveopt'/>
>       <feature name='mbm_total'/>
>       <feature name='mbm_local'/>
>       <feature name='pdpe1gb'/>
>       <feature name='abm'/>
>       <feature name='invtsc'/>
>       <pages unit='KiB' size='4'/>
>       <pages unit='KiB' size='2048'/>
>       <pages unit='KiB' size='1048576'/>
>     </cpu>
>
> Regards,
> Oisin
>
> Oisin O'Malley
> Systems Engineer
> Iocane Pty Ltd
> 763 South Road
> Black Forest SA 5035
>
> Office:+61 (8) 8413 1010
> Fax:+61 (8) 8231 2050
> Email:oisin.omalley at iocane.com.au
> Web:www.iocane.com.au
>
> Better for business
>
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> CentOS-virt at centos.org
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