Re: [RFC PATCH, x86]: Disable CPA cache flush for selfsnoop targets

[Andy Lutomirski]

On Thu, Jul 11, 2019 at 1:13 AM Uros Bizjak <ubizjak@xxxxxxxxx> wrote:
>
> Recent patch [1] disabled a self-snoop feature on a list of processor
> models with a known errata, so we are confident that the feature
> should work on remaining models also for other purposes than to speed
> up MTRR programming.
>
> I would like to resurrect an old patch [2] that avoids calling clflush
> and wbinvd
> to invalidate caches when CPU supports selfsnoop.

The big question here is: what are all the reasons that we might need
to flush?  Certainly, for stuff like SEV and MKTME, we need to flush
regardless of any self-snoop capability.