Re: [PATCH] KVM : Fix read/write to IA32_FEATURE_CONTROL MSR in nested virt

[Gleb Natapov <gleb@redhat.com>]

On Thu, Jul 04, 2013 at 01:21:51PM +0200, Paolo Bonzini wrote:
> Il 04/07/2013 13:12, Gleb Natapov ha scritto:
> > > I don't like that it requires a firmware change in order to use nested
> > > VMX (at least for hypervisors that read the MSR).  "Worse emulation" and
> > > "better emulation + new firmware" are indistiguishable from the point of
> > > view of anyone except the firmware.
> > > 
> > > IMO there is no reason for a better emulation that no one would care
> > > about _and_ could look like a regression when updating to a newer kernel.
> >
> > That is why now is the good time to do that since nested vmx is not
> > widely used. When it will be widely used the change will be impossible
> > to do for reason you age giving. So it is now or never.
> 
> I think it is a can of worms.  For example, should this be
> conditionalized on running under QEMU?  Under UEFI, TianoCore should be
> doing it, not SeaBIOS.  And for CoreBoot, should it be done by CoreBoot
> or SeaBIOS?  (How do people use KVM together with CoreBoot?)
> 
This is not the first thing that firmware need to initialize. I let
firmware guys fight over who is doing it, we just model HW. FWIW for
Seabios patch would be trivial.

> So I still prefer never... :)
> 
This is a "can of worms" IMO. What we decide to init in KVM next to
relieve firmware from its duty? This is "other hypervisor" way, in KVM
we just model HW.

--
			Gleb.