Messages in this thread | | | Date | Fri, 26 Mar 2021 11:06:20 +0100 | From | Borislav Petkov <> | Subject | Re: Why does glibc use AVX-512? |
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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
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