Messages in this thread | | | From | Dan Williams <> | Date | Mon, 24 May 2021 16:39:49 -0700 | Subject | Re: [RFC v2-fix-v2 2/2] x86/tdx: Ignore WBINVD instruction for TDX guest |
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On Mon, May 24, 2021 at 4:32 PM Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> wrote: > > Functionally only DMA devices can notice a side effect from > WBINVD's cache flushing. But, TDX does not support DMA, > because DMA typically needs uncached access for MMIO, and > the current TDX module always sets the IgnorePAT bit, which > prevents that.
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. 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.
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