Re: [PATCH 10/54] KVM: x86/mmu: Replace EPT shadow page shenanigans with simpler check

[Paolo Bonzini]

On 23/06/21 18:17, Sean Christopherson wrote:
> > What the commit message doesn't say is, did we miss this
> > opportunity all along, or has there been a change since commit
> > 47c42e6b4192 ("KVM: x86: fix handling of role.cr4_pae and rename it
> > to 'gpte_size'", 2019-03-28) that allows this?
>
> The code was wrong from the initial "unsync" commit.  The 4-byte vs.
> 8-byte check papered over the real bug, which was that the roles were
> not checked for compabitility.  I suspect that the bug only
> manisfested as an observable problem when the GPTE sizes mismatched,
> thus the PAE check was added.

I meant that we really never needed is_ept_sp, and you could have used 
the simpler check already at the time you introduced gpte_is_8_bytes. 
But anyway I think we're in agreement.

Paolo