Re: [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is RUNNABLE

From: Edgecombe, Rick P
Date: Thu Jun 12 2025 - 19:39:45 EST


On Wed, 2025-06-11 at 07:42 -0700, Sean Christopherson wrote:
> If there's a *legitimate* use case where the guest wants to ACCEPT a subset of
> memory, then there should be an explicit TDCALL to request that the unwanted
> regions of memory be unmapped.  Smushing everything into implicit behavior has
> obvioulsy created a giant mess.

Hi, still digging on if there is any possible use.

I think this may need a guest opt-in, so the guest can say it can handle errors
for both smaller and larger page size matches. So it may not matter if there is
a rare usage or not. If KVM finds the guest opts-in (how to do that TBD), it can
start mapping at the host level. If KVM doesn't see the opt-in, the guest gets
4k pages.