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

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Message-ID: <CAHCEeh+d+ya6+Xrh8hdWVSGo2kk_rZ8PV2eMM-2LLaOojAaBtQ@mail.gmail.com>
Date:   Mon, 1 Jun 2020 16:15:14 +0800
From:   Greentime Hu <greentime.hu@...ive.com>
To:     Guo Ren <guoren@...nel.org>
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

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.

> As spec 0.9 mentioned above, vxrm and vxsat are thread storage duration.
>
> When timer 's interrupt coming, we still need to save them in context_switch.
>
> On Tue, May 26, 2020 at 3:03 PM Greentime Hu <greentime.hu@...ive.com> wrote:
> >
> > From: Guo Ren <guoren@...ux.alibaba.com>
> >
> > Follow the riscv vector spec to add new csr number.
> >
> > [greentime.hu@...ive.com: update the defined value based on new spec and
> > remove unused ones]
> > Signed-off-by: Greentime Hu <greentime.hu@...ive.com>
> > Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> > ---
> >  arch/riscv/include/asm/csr.h | 16 ++++++++++++++--
> >  1 file changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> > index 8e18d2c64399..cc13626c4bbe 100644
> > --- a/arch/riscv/include/asm/csr.h
> > +++ b/arch/riscv/include/asm/csr.h
> > @@ -24,6 +24,12 @@
> >  #define SR_FS_CLEAN    _AC(0x00004000, UL)
> >  #define SR_FS_DIRTY    _AC(0x00006000, UL)
> >
> > +#define SR_VS           _AC(0x00000600, UL) /* Vector Status */
> > +#define SR_VS_OFF       _AC(0x00000000, UL)
> > +#define SR_VS_INITIAL   _AC(0x00000200, UL)
> > +#define SR_VS_CLEAN     _AC(0x00000400, UL)
> > +#define SR_VS_DIRTY     _AC(0x00000600, UL)
> > +
> >  #define SR_XS          _AC(0x00018000, UL) /* Extension Status */
> >  #define SR_XS_OFF      _AC(0x00000000, UL)
> >  #define SR_XS_INITIAL  _AC(0x00008000, UL)
> > @@ -31,9 +37,9 @@
> >  #define SR_XS_DIRTY    _AC(0x00018000, UL)
> >
> >  #ifndef CONFIG_64BIT
> > -#define SR_SD          _AC(0x80000000, UL) /* FS/XS dirty */
> > +#define SR_SD          _AC(0x80000000, UL) /* FS/VS/XS dirty */
> >  #else
> > -#define SR_SD          _AC(0x8000000000000000, UL) /* FS/XS dirty */
> > +#define SR_SD          _AC(0x8000000000000000, UL) /* FS/VS/XS dirty */
> >  #endif
> >
> >  /* SATP flags */
> > @@ -114,6 +120,12 @@
> >  #define CSR_PMPADDR0           0x3b0
> >  #define CSR_MHARTID            0xf14
> >
> > +#define CSR_VSTART             0x8
> > +#define CSR_VCSR               0xf
> > +#define CSR_VL                 0xc20
> > +#define CSR_VTYPE              0xc21
> > +#define CSR_VLENB              0xc22
> > +
> >  #ifdef CONFIG_RISCV_M_MODE
> >  # define CSR_STATUS    CSR_MSTATUS
> >  # define CSR_IE                CSR_MIE
> > --
> > 2.26.2
> >
> >
>
>
> --
> Best Regards
>  Guo Ren
>
> ML: https://lore.kernel.org/linux-csky/