On Mon, Feb 04, 2019 at 03:24:23PM -0800, Dave Hansen wrote: > Actually, there's one part of all this that I forgot. Will split lock > detection be enumerated _widely_? IOW, will my laptop in 5 years > enumerate support for it?
I would bloody hope so. Just for giggles, create an little program that does LOCK prefix across a line or page boundary in a while(1) loop and 'enjoy' your laptop experience. > If so, we surely don't want to enable this > everyhwhere: it will break old apps. Doesn't that mean that we need > both feature detection and another separate bit for folks to opt-in? No, we very much do want to default enable this everywhere. We might want to provide some chicken bits, like a (inheritable) PRCTL or ELF flag to disable it for those broken apps. But realistically, any app that triggers this is non-portable already, most (if not all) the RISC architecture would already kill it with SIGBUS for this. We very much want the kernel _AND_ firmware to be #AC clean, always, everywhere. Heck, I'd love for #AC to be even stronger and not only trigger on cross-line.