On 11/24/21 10:36 PM, Wei ZHOU wrote:
> Hi Wido,
>
> I think it is not good to run an environment with two ubuntu/qemu versions.
> It always happens that some cpu features are supported in the higher
> version but not supported in the older version.
> From my experience, the migration from older version to higher version
> works like a charm, but there were many issues in migration from higher
> version to older version.
>
I understand. But with a large amount of hosts and working your way
through upgrades you sometimes run into these situations. Therefor it
would be welcome if it works.
> I do not have a solution for you. I have tried to hack
> /etc/libvirt/hooks/qemu but it didn't work.
> Have you tried with other cpu models like x86_Opteron_G5 ? you can find the
> cpu features of each cpu model in /usr/share/libvirt/cpu_map/
>
I have not tried that yet, but I can see if that works.
The EPYC-IBPB CPU model is identical on 18.04 and 20.04, but even using
that model we can't seem to migrate as it complains about the 'npt' feature.
Wido
> Anyway, even if the vm migration succeeds, you do not know if vm works
> fine. I believe the best solution is upgrading all hosts to the same OS
> version.
>
> -Wei
>
> On Tue, 23 Nov 2021 at 16:31, Wido den Hollander <w...@widodh.nl> wrote:
>
>> Hi,
>>
>> I'm trying to debug an issue with live migrations between Ubuntu 18.04
>> and 20.04 machines each with different CPUs:
>>
>> - Ubuntu 18.04 with AMD Epyc 7552 (Rome)
>> - Ubuntu 20.04 with AMD Epyc 7662 (Milan)
>>
>> We are currently using this setting:
>>
>> guest.cpu.mode=custom
>> guest.cpu.model=EPYC
>>
>> This does not allow for live migrations:
>>
>> Ubuntu 20.04 with Epyc 7662 to Ubuntu 18.04 with Epyc 7552 fails
>>
>> "ExecutionException : org.libvirt.LibvirtException: unsupported
>> configuration: unknown CPU feature: npt"
>>
>> So we tried to define a set of features manually:
>>
>> guest.cpu.features=3dnowprefetch abm adx aes apic arat avx avx2 bmi1
>> bmi2 clflush clflushopt cmov cr8legacy cx16 cx8 de f16c fma fpu fsgsbase
>> fxsr fxsr_opt lahf_lm lm mca mce misalignsse mmx mmxext monitor movbe
>> msr mtrr nx osvw pae pat pclmuldq pdpe1gb pge pni popcnt pse pse36
>> rdrand rdseed rdtscp sep sha-ni smap smep sse sse2 sse4.1 sse4.2 sse4a
>> ssse3 svm syscall tsc vme xgetbv1 xsave xsavec xsaveopt -npt -x2apic
>> -hypervisor -topoext -nrip-save
>>
>> This results in this going into the XML:
>>
>> <feature policy='disable' name='npt'/>
>>
>> You would say that works, but then the target host (18.04 with the 7552)
>> says it doesn't support the feature 'npt' and the migration still fails.
>>
>> Now we could ofcourse use the kvm64 CPU from Qemu, but that's lacking so
>> many features that for example TLS offloading isn't available.
>>
>> I also tried to set 'EPYC-Rome' on the Ubuntu 20.04 hypervisor, but it
>> then complains on the Ubuntu 18.04 hypervisor that the CPU 'EPYC-Rome'
>> is unknown as the 18.04 hypervisor doesn't have that profile.
>>
>> Any ideas on how to get this working?
>>
>> Wido
>>
>
