Re: [RFC] TDX module configurability of 0x80000008

[Sean Christopherson <seanjc@google.com>]

On Wed, May 08, 2024, Xiaoyao Li wrote:
> On 4/25/2024 12:55 AM, Edgecombe, Rick P wrote:
> > One of the TDX module features is called MAXPA_VIRT. In short, it is similar to
> > KVM’s allow_smaller_maxphyaddr. It requires an explicit opt-in by the VMM, and
> > allows a TD’s 0x80000008.EAX[7:0] to be configured by the VMM. Accesses to
> > physical addresses above the specified value by the TD will cause the TDX module
> > to inject a mostly correct #PF with the RSVD error code set. It has to deal with
> > the same problems as allow_smaller_maxphyaddr for correctly setting the RSVD
> > bit. I wasn’t thinking to push this feature for KVM due the movement away from
> > allow_smaller_maxphyaddr and towards 0x80000008.EAX[23:16].
> > 
> 
> I would like to get your opinion of the MAXPA_VIRT feature of TDX. What is
> likely the KVM's decision on it? Won't support it due to it has the same
> limitation of allow_smaller_maxphyaddr?

Not supporting MAXPA_VIRT has my vote.  I'm of the opinion that allow_smaller_maxphyaddr
should die a horrible, fiery death :-)