On Thu, Nov 02, 2017 at 12:38:05PM -0700, Dave Hansen wrote: > On 11/02/2017 12:01 PM, Will Deacon wrote: > > On Tue, Oct 31, 2017 at 03:31:46PM -0700, Dave Hansen wrote: > >> KAISER makes it harder to defeat KASLR, but makes syscalls and > >> interrupts slower. These patches are based on work from a team at > >> Graz University of Technology posted here[1]. The major addition is > >> support for Intel PCIDs which builds on top of Andy Lutomorski's PCID > >> work merged for 4.14. PCIDs make KAISER's overhead very reasonable > >> for a wide variety of use cases. > > I just wanted to say that I've got a version of this up and running for > > arm64. I'm still ironing out a few small details, but I hope to post it > > after the merge window. We always use ASIDs, and the perf impact looks > > like it aligns roughly with your findings for a PCID-enabled x86 system. > > Welcome to the party! > > I don't know if you've found anything different, but there been woefully > little code that's really cross-architecture. The kernel task > stack-mapping stuff _was_, but it's going away. The per-cpu-user-mapped > section stuff might be common, I guess. I currently don't have anything mapped other than the trampoline page, so I haven't had to do per-cpu stuff (yet). This will interfere with perf tracing using SPE, but if that's the only thing that needs it then it's a hard sell, I think. > Is there any other common infrastructure that we can or should be sharing? I really can't see anything. My changes are broadly divided into: * Page table setup * Exception entry/exit via trampoline * User access (e.g. get_user) * TLB invalidation * Context switch (backend of switch_mm) which is all deeply arch-specific. Will -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
