Re: [RFC v2-fix-v3 1/1] x86/tdx: Skip WBINVD instruction for TDX guest

[Dave Hansen]

On 6/8/21 2:35 PM, Kuppuswamy Sathyanarayanan wrote:
> Persistent memory is also currently not supported. Another code
> path that uses WBINVD is the MTRR driver, but EPT/virtualization
> always disables MTRRs so those are not needed. This all implies
> WBINVD is not needed with current TDX.

It's one thing to declare something unsupported.  It's quite another to
declare it unsupported and then back it up with code to ensure that any
attempted use is thwarted.

This patch certainly shows us half of the solution.  But, to be
complete, we also need to see the other half: where is the patch or
documentation for why it is not *possible* to encounter persistent
memory in a TDX guest?

BTW, "persistent memory" is much more than Intel Optane DCPMM.