Messages in this thread | | | From | Uros Bizjak <> | Date | Thu, 11 Jul 2019 21:00:06 +0200 | Subject | Re: [RFC PATCH, x86]: Disable CPA cache flush for selfsnoop targets |
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On Thu, Jul 11, 2019 at 4:39 PM Andy Lutomirski <luto@kernel.org> wrote: > > On Thu, Jul 11, 2019 at 1:13 AM Uros Bizjak <ubizjak@gmail.com> 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.
No AMD target defines self-snoop capability, and set_memory_encrypted forces cache clearing in __set_memory_enc_dec:
/* * Before changing the encryption attribute, we need to flush caches. */ cpa_flush(&cpa, 1);
Uros.
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