Re: [PATCH V3 14/22] LoongArch: Add signal handling support

[Richard Henderson]

On 9/19/21 7:36 PM, Huacai Chen wrote:
> Hi, Arnd,
>
> On Sun, Sep 19, 2021 at 5:59 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > On Sat, Sep 18, 2021 at 9:12 AM Huacai Chen <chenhuacai@xxxxxxxxx> wrote:
> > > On Sat, Sep 18, 2021 at 5:10 AM Eric W. Biederman <ebiederm@xxxxxxxxxxxx> 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.


r~