linux-kernel - Re: [PATCH] riscv: require alternatives framework when selecting FPU support

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Message-ID: <CAHmME9qEbUP7cq-iofN=ruSWhsHUva+qqavfEpNzDK_BjQVqxw@mail.gmail.com>
Date:   Wed, 22 Mar 2023 21:19:50 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Conor Dooley <conor@...nel.org>
Cc:     Andrew Jones <ajones@...tanamicro.com>,
        Jisheng Zhang <jszhang@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        regressions@...mhuis.info, regressions@...ts.linux.dev
Subject: Re: [PATCH] riscv: require alternatives framework when selecting FPU support

On Wed, Mar 22, 2023 at 9:05 PM Conor Dooley <conor@...nel.org> wrote:
>
> On Wed, Mar 22, 2023 at 07:44:13PM +0000, Conor Dooley wrote:
> > On Wed, Mar 22, 2023 at 08:26:10PM +0100, Andrew Jones wrote:
> > > On Wed, Mar 22, 2023 at 03:17:13PM +0000, Conor Dooley wrote:
> > > > On Wed, Mar 22, 2023 at 01:46:31PM +0100, Andrew Jones wrote:
> >
> > > > > (It's tempting to just select RISCV_ALTERNATIVE from RISCV, but maybe we
> > > > >  can defer that wedding a bit longer.)
> > > >
> > > > At that point, the config option should just go away entirely, no?
> > >
> > > Ah, yes, and that makes the idea even more attractive, as we could remove
> > > several ifdefs.
> >
> > I went and did the cursory check, it's not compatible with XIP_KERNEL so
> > dropping the option entirely probably isn't a possibility :/
>
> What I said is only now sinking in. We're now going to be disabling FPU
> support on XIP kernels with this patch.
> Well, technically not this patch since it wouldn't have built without
> Jason's changes, but that doesn't seem like the right thing to do...

I suppose you could have riscv_has_extension_*() fall back to
something that doesn't use alternatives on XIP kernels.