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

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Date:   Tue, 9 Mar 2021 12:33:57 +0100
From:   Heinrich Schuchardt <xypron.glpk@....de>
To:     Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>
Cc:     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 08.03.21 11:55, Anup Patel wrote:
> On Mon, Mar 8, 2021 at 1:19 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.

Here is the OpenSBI correction:

[PATCH 1/1] include: sbi: SBI function IDs for RFENCE extension
http://lists.infradead.org/pipermail/opensbi/2021-March/000703.html

Best regards

Heinrich

>>
>> Should we just fix the spec instead ?
>
> I would not recommend that because RFENCE is part of the released SBI v0.2 spec.
>
> We have to be more careful in software to follow the spec correctly.
>
> Regards,
> Anup
>
>>
>>> 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

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