Messages in this thread |  | | Date | Tue, 27 Dec 2022 15:49:39 -0600 | Subject | Re: [PATCH Part2 v6 07/49] x86/sev: Invalid pages from direct map when adding it to RMP table | From | "Kalra, Ashish" <> |
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Hello Boris,
On 12/19/2022 2:08 PM, Borislav Petkov wrote: > On Mon, Dec 19, 2022 at 09:00:26AM -0600, Michael Roth wrote: >> We implemented this approach for v7, but it causes a fairly significant >> performance regression, particularly for the case for npages > 1 which >> this change was meant to optimize. >> >> I still need to dig in a big but I'm guessing it's related to flushing >> behavior. > > Well, AFAICT, change_page_attr_set_clr() flushes once at the end. > > Don't you need to flush when you modify the direct map? >
Milan onward, there is H/W support for coherency between mappings of the same physical page with different encryption keys, so AFAIK, there should be no need to flush during page state transitions, where we invoke these direct map interface functions for re-mapping/invalidating pages.
I don't know if there is any other reason to flush after modifying the direct map ?
Thanks, Ashish
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