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

[Sean Christopherson <seanjc@google.com>]

On Fri, Jun 13, 2025, Rick P Edgecombe wrote:
> On Fri, 2025-06-13 at 09:32 +0800, Yan Zhao wrote:
> > > > Eww, no.  Having to react on _every_ EPT violation would be annoying,
> > > > and trying to debug issues where the guest is mixing options would
> > > > probably be a nightmare.
> > > > 
> > > > I was thinking of something along the lines of an init-time or
> > > > boot-time opt- in.
> > > 
> > > Fair.
> > 
> > Agreed.
> 
> Arg, I just realized a one-way opt-in will have a theoretical gap. If the guest
> kexec's, the new kernel will need to match the opt-in.

All the more reason to make this a property of the VM that is passed via
"struct td_params".  I.e. put the onus on the owner of the VM to ensure their
kernel(s) have been updated accordingly.

I understand that this could be painful, but honestly _all_ of TDX and SNP is
painful for the guest.  E.g. I don't think it's any worse than the security
issues with TDX (and SNP) guests using kvmclock (which I'd love some reviews on,
btw).

https://lore.kernel.org/all/20250227021855.3257188-35-seanjc@google.com