Re: [BUG] Migration hv_time rollback

[Vitaly Kuznetsov]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 16/09/20 13:29, Dr. David Alan Gilbert wrote:
>>> I have tracked the bug to the fact that `kvmclock` is not exposed and
>>> disabled from qemu PoV but is in fact used by `hv-time` (in KVM).
>>>
>>> I think we should enable the `kvmclock` (qemu device) if `hv-time` is
>>> present and add Hyper-V support for the `kvmclock_current_nsec`
>>> function.
>
> Yes, this seems correct.  I would have to check but it may even be
> better to _always_ send kvmclock data in the live migration stream.
>

The question I have is: with 'kvm=off', do we actually restore TSC
reading on migration? (and I guess the answer is 'no' or Hyper-V TSC
page would 'just work' I guess). So yea, maybe dropping the
'cpu->env.features[FEAT_KVM]' check is the right fix.

-- 
Vitaly