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

[Paolo Bonzini]

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).

Paolo