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
