On Tue, May 04, 2021 at 11:25:31PM -0700, Kees Cook wrote: > On Tue, May 04, 2021 at 05:30:23PM -0700, Rick Edgecombe wrote: > > > Performance impacts > > =================== > > Setting direct map permissions on whatever random page gets allocated for a > > page table would result in a lot of kernel range shootdowns and direct map > > large page shattering. So the way the PKS page table memory is created is > > similar to this module page clustering series[2], where a cache of pages is > > replenished from 2MB pages such that the direct map permissions and associated > > breakage is localized on the direct map. In the PKS page tables case, a PKS > > key is pre-applied to the direct map for pages in the cache. > > > > There would be some costs of memory overhead in order to protect the direct > > map page tables. There would also be some extra kernel range shootdowns to > > replenish the cache on occasion, from setting the PKS key on the direct map of > > the new pages. I don’t have any actual performance data yet. > > What CPU models are expected to have PKS? Supervisor Memory Protection Keys (PKS) is a feature which is found on Intel’s Sapphire Rapids (and later) “Scalable Processor” Server CPUs. It will also be available in future non-server Intel parts. Also qemu has some support as well. https://www.qemu.org/2021/04/30/qemu-6-0-0/ Ira
