Resend due to typo in tag. s/PPF/BPF/ However, I also realized one should fill out the google form now. I'll do that straight away. Thanks, Ira On Fri, Feb 25, 2022 at 08:10:30AM -0800, Ira Weiny wrote: > Hello, > > Protection Key Supervisor (PKS) presents a way to control access to a large > domain of memory quickly, without a page table walk or TLB flush, as well as > with finer granularity; allowing protection control on individual threads. > > Multiple areas of memory have been identified as candidates to be protected > with PKS. These include the initial use case persistent memory (PMEM), page > tables[1], kernel secret keys[2], and the page cache.[3] Like PMEM the page > cache presents a significant surface area where stray writes, or other bugs, > could corrupt data permanently. > > I would like to discuss the ramifications of being able to change memory > permissions in this new way. While PKS has a lot to offer it does not come for > free. One trade off is the loss of direct access via page_address() in > !HIGHMEM builds. > > Already PMEM's faced challenges in the leverage of kmap/kunmap. While the page > cache should be able to leverage this work, this is driving a redefinition of > what kmap means. Especially since the HIGHMEM use case is increasingly > meaningless on modern machines. > > Ira Weiny > > [1] https://lore.kernel.org/lkml/20210830235927.6443-2-rick.p.edgecombe@xxxxxxxxx/ > [2] https://lore.kernel.org/lkml/20201009201410.3209180-3-ira.weiny@xxxxxxxxx/ > [3] https://lwn.net/Articles/883352/
