linux-kernel - Re: [RFC PATCH v4 05/13] riscv: Add new csr defines related to vector extension

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Message-ID: <CAJF2gTRk3hUmqOb4dhCWhLZq6tznwVLWGe5M4jY4D+DS+P6vNQ@mail.gmail.com>
Date:   Mon, 1 Jun 2020 16:59:47 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Greentime Hu <greentime.hu@...ive.com>
Cc:     Guo Ren <guoren@...ux.alibaba.com>,
        Vincent Chen <vincent.chen@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [RFC PATCH v4 05/13] riscv: Add new csr defines related to vector extension

On Mon, Jun 1, 2020 at 4:15 PM Greentime Hu <greentime.hu@...ive.com> wrote:
>
> Guo Ren <guoren@...nel.org> 於 2020年5月31日 週日 上午9:56寫道：
> >
> > Hi Greentime,
> >
> > Why remove vxrm and xstat ?
> >
> > > Appendix B: Calling Convention
> > > In the RISC-V psABI, the vector registers v0-v31 are all caller-saved. The vstart, vl, and vtype CSRs are also caller-saved.
> > > The vxrm and vxsat fields have thread storage duration.
> >
> Hi Guo,
>
> https://github.com/riscv/riscv-v-spec/blob/master/v-spec.adoc#vector-control-and-status-register-vcsr
> "The vxrm and vxsat separate CSRs can also be accessed via fields in
> the vector control and status CSR, vcsr."
>
> Since vcsr will save all these information, I think it should be ok to
> save vcsr only.

Got it, it's similar with fcsr & frm & fflags.

Acked-by: Guo Ren <guoren@...nel.org>

-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/