On Thu, Mar 25, 2021 at 09:38:24PM -0700, Andy Lutomirski wrote: > I think we should seriously consider solutions in which, for new > tasks, XCR0 has new giant features (e.g. AMX) and possibly even > AVX-512 cleared, and programs need to explicitly request enablement.
I totally agree with making this depend on an explicit user request, but... > This would allow programs to opt into not saving/restoring across > signals or to save/restore in buffers supplied when the feature is > enabled. This has all kinds of pros and cons, and I'm not sure it's a > great idea. But, in the absence of some change to the ABI, the > default outcome is that, on AMX-enabled kernels on AMX-enabled > hardware, the signal frame will be more than 8kB, and this will affect > *every* signal regardless of whether AMX is in use. ... what's stopping the library from issuing that new ABI call before it starts the app and get <insert fat feature here> automatically enabled for everything by default? And then we'll get the lazy FPU thing all over again. So the ABI should be explicit user interaction or a kernel cmdline param or so. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette