Date: Thu, 16 Mar 2017 11:41:14 +0100 From: Sylvain Garrigues <sylvain@sylvaingarrigues.com> To: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: Is CPUTYPE=cortex-A7 supposed to work? Message-ID: <E6BC9F77-F65B-4918-9E22-3BFECA268E30@sylvaingarrigues.com> In-Reply-To: <79EBD44B-2C2D-4394-A90C-DF494A049F20@dsl-only.net> References: <871suc3nv8.fsf@news-spur.riddles.org.uk> <CANCZdfq4EwH%2B_9FVNai8s6Y-gdTjHJ8dNkJwSrnF%2BSAkdwvYdg@mail.gmail.com> <8737ely05c.fsf@news-spur.riddles.org.uk> <CANCZdfpftVHaPahTOP0vxB-FR%2BKtpqY9JMJr=F2DGifD0fhKMQ@mail.gmail.com> <87wpbxw3yd.fsf@news-spur.riddles.org.uk> <79EBD44B-2C2D-4394-A90C-DF494A049F20@dsl-only.net>
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Hi, > Le 10 mars 2017 =C3=A0 18:51, Mark Millard <markmi at dsl-only.net> a = =C3=A9crit : >=20 > So overall: >=20 > If the ABI stays as it is for 11 (or 12), floating point in > general (VFP with or without NEON) and Integer NEON can be > broken when signals are involved that allow the code to keep > going instead of exiting the process. (This means all NEON use > is subject to the issue.) Reading through this thread I understand one can definitely get into = trouble with a system which has CPUTYPE=3Dcortex-a7 in make.conf (or = even some -mcpu=3Dcortex-a7 in some CFLAGS variable there), especially = if a port does FP stuff in a signal handler (because FP registers are = not well preserved / restored on the kernel side). As Michal wrote: > Unfortunately, on armv6, the VFP part of kernel <-> userland = interaction > is broken from day 1.=20 This kind of frightens me, is there any plan to fix it soon (I=E2=80=99d = help if I could)?=20 I understand Andrew's tiny patch = (https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D180669&action=3Ddif= f = <https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D180669&action=3Ddif= f>) fixes VFP interactions during signal handling, would that fix all = the "VFP part of kernel <-> userland interaction =C2=BB? Is fixing VFP already being discussed in a Phabricator=E2=80=99s review = or are you guys discussing a backward-compatible alternative to = ABI-breaking (although we are not required to do so since we are still = tier-2) elsewhere? Needless to say, I see strong interest in being able to just dump = "CPUTYPE=3D<my cpu variant>" in make.conf on arm and be confident my = system will be fine and fine-tuned, just like I do for all my x86/amd64 = machines with such a flag. Have all a good day, Sylvain=
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