Hi! On Tue, May 24, 2022 at 07:38:28PM +1000, Nicholas Piggin wrote: > Thanks for all the comments and corrections. It should be nearing the > point where it is useful now. Yes I do think it would be useful to align > this more with OpenPOWER docs (and possibly eventually move it into the > ABI, given that's the allocator of these numbers) but that's not > done yet.
The auxiliary vector is a Linux/glibc thing, it should not be described in more generic ABI documents. It is fine where you have it now afaics. > +Where software relies on a feature described by a HWCAP, it should check the > +relevant HWCAP flag to verify that the feature is present before attempting > to > +make use of the feature. > + > +Features should not be probed through other means. When a feature is not > +available, attempting to use it may result in unpredictable behaviour, and > +may not be guaranteed to result in any reliable indication that the feature > +is unavailable. Traditionally VMX was tested for by simply executing an instruction and catching SIGILL. This is portable even. This has worked fine for over two decades, it's a bit weird to declare this a forbidden practice now :-) It certainly isn't recommended for more complex and/or newer things. > +verstions. (typo. spellcheck maybe?) Segher
