Re: [Qemu-devel] [PATCH RFC 4/8] i386/kvm: Implement 'hv-all' pass-through mode

[Vitaly Kuznetsov]

Eduardo Habkost <address@hidden> writes:

>
> If libvirt is involved, it's much simpler and safer to use
> something like <cpu mode="host-model">, which generates a
> migration-safe CPU configuration based on the current host.  Live
> migration support with "-cpu host" is only useful for experiments
> and carefully controlled environments.
>
> Is there a real need to make hv-all migratable?  What would be
> the use case, exactly?  If there's no clear use case, I would
> recommend making it a migration blocker.

There's no clear use-case; I noticed that we keep adding Hyper-V
enlightenments and these make Windows' life on KVM easier so we
recommend enabling them all (and, with an exception for hv-evmcs, which
I also don't enable with hv-all, I'm unawere of cases which would
require disabling certain Hyper-V enlightenments).

hv-all is mostly a convenience feature. I plan to take a look at
'host-model' to see if we can borrow some ideas from there (that would
actually be ideal - build a set of 'hv-*' enlightenments based on
capabilites of the current host) but I'm also not totally against
keeping it the way it is and making it a migration blocker for the time
being (and making it a 'developer-only' feature).

-- 
Vitaly