On Tue, 2021-05-04 at 23:25 -0700, Kees Cook wrote: > > infrastructure follow-on’s are planned to enable keys to be set to > > the same > > permissions globally. Since this usage needs a key to be set globally > > read-only by default, a small temporary solution is hacked up in > > patch 8. Long > > term, PKS protected page tables would use a better and more generic > > solution > > to achieve this. > > > > [1] > > https://lore.kernel.org/lkml/20210401225833.566238-1-ira.weiny@xxxxxxxxx/ > > Ah, neat! > > > [2] > > https://lore.kernel.org/lkml/20210405203711.1095940-1-rick.p.edgecombe@xxxxxxxxx/ > > Ooh. What does this do for performance? It sounds like less TLB > pressure, IIUC? Yea, less TLB pressure, faster page table walks in theory. There was some testing that showed having all 4k pages was bad for performance: https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@xxxxxxxxxxxxxxx/ I'm not sure exactly how much breakage is needed before problems start to show up, but there was also someone posting that large amounts of tracing was noticeable for their workload.
