Re: [PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level

[Paolo Bonzini]

On 10/08/21 09:40, Yu Zhang wrote:
> About "host can't easily mirror L1's desired paging mode", could you please elaborate?
> Thanks!

Shadow pgae tables in KVM will always have 3 levels on 32-bit machines 
and 4/5 levels on 64-bit machines.  L1 instead might have any number of 
levels from 2 to 5 (though of course not more than the host has).

Therefore, when shadowing 32-bit NPT page tables, KVM has to add extra 
fixed levels on top of those that it's shadowing.  See 
mmu_alloc_direct_roots for the code.

Paolo