Re: [PATCH v2 00/15] SHA-3 library

[Heiko Carstens <hca@linux.ibm.com>]

On Wed, Oct 29, 2025 at 08:33:45PM +0000, Eric Biggers wrote:
> (By the way, I recommend defining named constants somewhere in
> arch/s390/ for the different facilities.  I borrowed the
> "test_facility(86)" from the existing code, which does not say what 86
> means.  After doing some research, it looks like it means MSA12.)

Not so surpringly this has been discussed several times in the
past. It would have been easy if each of those bits would represent
exactly one facility, but then there is e.g. bit 46 which means:

the distinct-operands, fast-BCR-serialization, high-word, and
population-count facilities, the interlocked-access facility 1, and
the load/store-on- condition facility 1 are installed in the
z/Architecture architectural mode

Some proposed to add defines like "FACILITY_MULTI_46", which is of
course pointless, since there is added benefit for just using plain
46. Alternatively it would be possible to have a define for each of
them. But if you need two or three of them for your code, then there
would be several tests needed - all for the same bit, and each one
generating a static branch - which also doesn't make too much sense.

So in the end we ended up with the conclusion to stick with the plain
numbers.

That said, users are still free to add aliases like e.g. cpu_has_vx(),
see arch/s390/include/asm/cpufeature.h. It is just not an all or
nothing approach.