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

From: Dave Hansen
Date: Tue Jun 08 2021 - 19:38:30 EST

On 6/8/21 4:32 PM, Dan Williams 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.
> Let's drop the last three paragraphs and just say something like:
> "This is one of a series of patches to usages of wbinvd for protected
> guests. For now this just addresses the one known path that TDX
> executes, ACPI reboot. Its usage can be elided because FOO reason and
> all the other ACPI_FLUSH_CPU_CACHE usages can be elided because BAR
> reason"

A better effort at transparency can be made here:

This patches the one WBINVD instance which has been encountered
in practice: ACPI reboot. Assume no other instance will be