Re: [RFC v2-fix-v2 2/2] x86/tdx: Ignore WBINVD instruction for TDX guest

From: Andi Kleen
Date: Mon May 24 2021 - 20:36:33 EST


I thought we discussed that there are other considerations for wbinvd
besides DMA? In any event this paragraph is actively misleading
because it disregards ACPI and Persistent Memory secure-erase whose
usages of wbinvd have nothing to do with DMA.

In this case they would be broken in KVM too.

I would much prefer a
patch to shutdown all the known wbinvd users as a precursor to this
patch rather than assuming it's ok to simply ignore it. You have
mentioned that TDX does not need to use those paths, but rather than
assume they can't be used why not do the audit to explicitly disable
them? Otherwise this statement seems to imply that the audit has not
been done.

We're not assuming it. We know it because KVM does it since forever.

All we want to do is do the same as KVM.