Re: [PATCH v5 03/15] KVM: SVM: Disable SEV/SEV-ES if NPT is disabled

[Paolo Bonzini]

On 22/04/21 18:15, Sean Christopherson wrote:
> > Support for 5-level page tables on NPT is not hard to fix and could be
> > tested by patching QEMU.  However, the !NPT case would also have to be fixed
> > by extending the PDP and PML4 stacking trick to a PML5.
>   
> Isn't that backwards?  It's the nested NPT case that requires the stacking trick.
> When !NPT is disabled in L0 KVM, 32-bit guests are run with PAE paging.  Maybe
> I'm misunderstanding what you're suggesting.

Yes, you're right.  NPT is easy but we would have to guess what the spec 
would say about MAXPHYADDR, while nNPT would require the stacking of a 
PML5.  Either way, blocking KVM is the easiest thing todo.

Paolo