linux-kernel - Re: [PATCH 1/1] RISC-V: correct enum sbi_ext_rfence_fid

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Message-ID: <CAOnJCU+NKwFdkg3X75opcDK1WHwcaK-MczyJhKCuECf5ydp9rg@mail.gmail.com>
Date:   Mon, 8 Mar 2021 00:03:42 -0800
From:   Atish Patra <atishp@...shpatra.org>
To:     Anup Patel <anup@...infault.org>
Cc:     Heinrich Schuchardt <xypron.glpk@....de>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atish.patra@....com>,
        Anup Patel <anup.patel@....com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Sean Anderson <seanga2@...il.com>
Subject: Re: [PATCH 1/1] RISC-V: correct enum sbi_ext_rfence_fid

On Sun, Mar 7, 2021 at 11:49 PM Atish Patra <atishp@...shpatra.org> wrote:
>
> On Sat, Mar 6, 2021 at 4:12 AM Anup Patel <anup@...infault.org> wrote:
> >
> > On Sat, Mar 6, 2021 at 11:19 AM Heinrich Schuchardt <xypron.glpk@....de> wrote:
> > >
> > > The constants in enum sbi_ext_rfence_fid should match the SBI
> > > specification. See
> > > https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.adoc#78-function-listing
> > >
> > > | Function Name               | FID | EID
> > > | sbi_remote_fence_i          |   0 | 0x52464E43
> > > | sbi_remote_sfence_vma       |   1 | 0x52464E43
> > > | sbi_remote_sfence_vma_asid  |   2 | 0x52464E43
> > > | sbi_remote_hfence_gvma_vmid |   3 | 0x52464E43
> > > | sbi_remote_hfence_gvma      |   4 | 0x52464E43
> > > | sbi_remote_hfence_vvma_asid |   5 | 0x52464E43
> > > | sbi_remote_hfence_vvma      |   6 | 0x52464E43
> > >
> > > Fixes: ecbacc2a3efd ("RISC-V: Add SBI v0.2 extension definitions")
> > > Reported-by: Sean Anderson <seanga2@...il.com>
> > > Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
> >
> > Good catch.
> >
> > I guess we never saw any issues because these calls are only used by
> > KVM RISC-V which is not merged yet. Further for KVM RISC-V, the HFENCE
> > instruction is emulated as flush everything on FPGA, QEMU, and Spike so
> > we did not notice any issue with KVM RISC-V too.
> >
>
> OpenSBI & Xvisor also define the same order as Linux kernel. The
> existing order(in Linux kernel)
> makes more sense w.r.to Lexicographic order as well.
>
> Should we just fix the spec instead ?
>

We do need to notify RustSBI & Diosix authors about this change in
case we decide to do so.
However, RustSBI added rfence support a few weeks back only [1]. I
could not find any rfence reference in Diosix.
Thus, the impact should be very minimal if the spec is fixed.

[1] https://github.com/luojia65/rustsbi/commit/6e06b4e8e96e05b69157dd5477d433cc932c8a64
> > Looks good to me.
> >
> > Reviewed-by: Anup Patel <anup@...infault.org>
> >
> > Regards,
> > Anup
> >
> > > ---
> > >  arch/riscv/include/asm/sbi.h | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> > > index 99895d9c3bdd..d7027411dde8 100644
> > > --- a/arch/riscv/include/asm/sbi.h
> > > +++ b/arch/riscv/include/asm/sbi.h
> > > @@ -51,10 +51,10 @@ enum sbi_ext_rfence_fid {
> > >         SBI_EXT_RFENCE_REMOTE_FENCE_I = 0,
> > >         SBI_EXT_RFENCE_REMOTE_SFENCE_VMA,
> > >         SBI_EXT_RFENCE_REMOTE_SFENCE_VMA_ASID,
> > > -       SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA,
> > >         SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA_VMID,
> > > -       SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA,
> > > +       SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA,
> > >         SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA_ASID,
> > > +       SBI_EXT_RFENCE_REMOTE_HFENCE_VVMA,
> > >  };
> > >
> > >  enum sbi_ext_hsm_fid {
> > > --
> > > 2.30.1
> > >
> > >
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@...ts.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv
>
>
>
> --
> Regards,
> Atish

-- 
Regards,
Atish

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