linux-kernel - Re: [PATCH 2/2] selftests/fpu: Add an FPU selftest

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Date:   Tue, 23 Jun 2020 23:32:30 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        jpa@...nelbug.mail.kapsi.fi, Dave Hansen <dave.hansen@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] selftests/fpu: Add an FPU selftest

On Tue, Jun 23, 2020 at 01:58:15PM -0700, Nick Desaulniers wrote:
> My point was more so about avoiding needless cc-option checks when
> they're tautological.

No, you're right. The oldest gcc we support is 4.8 and that eats -msse2
just fine.

> When Andy says "consider dropping the problematic GCC version" I
> wonder if it was meant *just for this selftest* as I suggested, or
> outright (which is untenable IMO, as it's a large jump to GCC 7.1+).

Yeah, he's been schooled now :)

> I'm not sure I agree, but I'll take feature detection any day over
> version detection.

Yeah, we had another issue recently with a funky compiler on some funky
distro:

https://lkml.kernel.org/r/CAEJqkgi3w%2BzvMkRBP4VtAewX1UJxrVNRQ03MtRN_yH-PwOOScQ@mail.gmail.com

and I have to say, I'm not at all happy about such subtle issues
stemming from how a distro builds its compiler and that having an impact
on the kernel build. But I guess this is the new reality now since we're
getting more and more married to the compiler.

> Guilty, your honor. :P
> 
> Maybe the feature test should be copy+pasta'd to those other places in
> the kernel, rather than the version check?

"pasta'd"- mmhmhm, tasty noodles. Good idea for lunch tomorrow, thanks!
:-)

But sure, if you feel bored. Let it soak a while first, though, until
all the builders and bots have seen it and haven't triggered moar funky
build errors.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette