Re: [Qemu-devel] [PATCH v3 1/2] i386/kvm: add support for Hyper-V reenlightenment MSRs

[Roman Kagan]

On Tue, Mar 20, 2018 at 03:32:27PM -0300, Eduardo Habkost wrote:
> The difference between both approaches is that checking just
> has_msr_hv_* would let a non-cooperating guest prevent itself
> from being migrated to an older host by writing a non-zero value
> to a MSR, even if hyperv support was not enabled in the VM
> configuration at all.  I don't think we want that.

Thinking some more of what we do want in this regard, I wonder if we're
doing the right thing by not generating #GP on access to MSRs whose
support is present in KVM but disabled via cpu properties in QEMU?

Roman.