Re: [Qemu-devel] [PATCH v2] target/i386: kvm: add VMX migration blocker

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/04/19 20:26, Cole Robinson wrote:
> On 11/20/18 6:44 AM, Dr. David Alan Gilbert wrote:
>> * Paolo Bonzini (pbonzini@redhat.com) wrote:
>>> Nested VMX does not support live migration yet.  Add a blocker
>>> until that is worked out.
>>>
>>> Nested SVM only does not support it, but unfortunately it is
>>> enabled by default for -cpu host so we cannot really disable it.
>>>
>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>
>> So I'm OK with this, but it does need a release note warning whenever it
>> goes in, because it'll surprise those who've already enabled nesting
>> but don't use it on all their VMs.
>>
> 
> We are hitting this in Fedora 30. Now that nested VMX is enabled by
> default at the kernel level, and virt-manager/boxes will use the
> equivalent of -cpu host by default, libvirt managedsave (migrate to
> file) and virt-manager snapshots (savevm) are rejected for default
> created VMs on intel. That's quite unfortunate.
> 
> Any ideas on how to resolve this?

I think the simplest solution is just to finish implementation of nested
VMX live migration and backport it to Fedora 30.

Paolo