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From:   Huacai Chen <chenhuacai@gmail.com>
Date:   Wed, 22 Sep 2021 10:43:09 +0800
Message-ID: <CAAhV-H5h9zNCmsOumR=_Bryj3-Qarbq7FH=uYbT_3++-8pwfPw@mail.gmail.com>
Subject: Re: [PATCH V3 14/22] LoongArch: Add signal handling support
To:     Richard Henderson <rth@twiddle.net>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Huacai Chen <chenhuacai@loongson.cn>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Airlie <airlied@linux.ie>,
        Jonathan Corbet <corbet@lwn.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Yanteng Si <siyanteng@loongson.cn>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
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Hi, Richard,

On Tue, Sep 21, 2021 at 5:14 AM Richard Henderson <rth@twiddle.net> wrote:
>
> On 9/19/21 7:36 PM, Huacai Chen wrote:
> > Hi, Arnd,
> >
> > On Sun, Sep 19, 2021 at 5:59 PM Arnd Bergmann <arnd@arndb.de> wrote:
> >>
> >> On Sat, Sep 18, 2021 at 9:12 AM Huacai Chen <chenhuacai@gmail.com> wrote:
> >>> On Sat, Sep 18, 2021 at 5:10 AM Eric W. Biederman <ebiederm@xmission.com> wrote:
> >>>> For example does LoongArch have a version without built in floating
> >>>> point support?
> >>>
> >>> Some of these structures seems need rethinking, But we really have
> >>> LoongArch-based MCUs now (no FP, no SMP, and even no MMU).
> >>
> >> NOMMU Linux is kind-of on the way out as interest is fading, so I hope you
> >> don't plan on supporting this in the future.
> >>
> >> Do you expect to see future products with MMU but no FP or no SMP?
> > OK, we will not care no-MMU hardware in Linux, but no-FP and no-SMP
> > hardware will be supported.
>
> Please consider requiring the FP registers to be present even on no-FP hardware.
>
> With this plus the FP data movement instructions (FMOV, MOVGR2FR, MOVFR2GR, FLD, FST), it
> is possible to implement soft-float without requiring a separate soft-float ABI.  This can
> vastly simplify compatibility and deployment.
OK, I'll send an updated version.

>
>
> r~