Re: [PATCH v3 0/9] KVM: Support guest MAXPHYADDR < host MAXPHYADDR

Jim Mattson
2020-07-10T17:13:24Z

On Fri, Jul 10, 2020 at 10:06 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 10/07/20 18:30, Jim Mattson wrote:
> >>
> >> This can be problem when having a mixed setup of machines with 5-level page
> >> tables and machines with 4-level page tables, as live migration can change
> >> MAXPHYADDR while the guest runs, which can theoretically introduce bugs.
> >
> > Huh? Changing MAXPHYADDR while the guest runs should be illegal. Or
> > have I missed some peculiarity of LA57 that makes MAXPHYADDR a dynamic
> > CPUID information field?
>
> Changing _host_ MAXPHYADDR while the guest runs, such as if you migrate
> from a host-maxphyaddr==46 to a host-maxphyaddr==52 machine (while
> keeping guest-maxphyaddr==46).

Ah, but what does that have to do with LA57?