On Thu, Apr 22, 2021, Paolo Bonzini wrote: > 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. How about I fold that into the s/lm_root/pml4_root rename[*]? I.e. make the blocking of PML5 a functional change, and the rename an opportunistic change? [*] https://lkml.kernel.org/r/20210318201131.3242619-1-seanjc@xxxxxxxxxx
