Re: [PATCH 17/15] KVM: X86: Ensure pae_root to be reconstructed for shadow paging if the guest PDPTEs is changed

Sean Christopherson
2021-12-13T16:55:07Z

On Sat, Dec 11, 2021, Paolo Bonzini wrote:
> On 12/11/21 07:56, Maxim Levitsky wrote:
> > > This apparently wasn't validated against a simple use case, let
> > > alone against things like migration with nested VMs, multliple L2s,
> > > etc...
> >
> > I did validate the *SREGS2* against all the cases I could (like
> > migration, EPT/NPT disabled/etc. I even started testing SMM to see
> > how it affects PDPTRs, and patched seabios to use PAE paging. I still
> > could have missed something.
>
> Don't worry, I think Sean was talking about patch 16 and specifically
> digging at me (who deserved it completely).

Yes, patch 16. My goal wasn't to dig at anyone, I just wanted to dramatically
emphasize how ridiculousy fragile and complex the PDPTR crud is due to the number
of edge cases.