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References: <20231017131456.2053396-1-cleger@rivosinc.com> <20231017131456.2053396-2-cleger@rivosinc.com>
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From:   Evan Green <evan@rivosinc.com>
Date:   Wed, 18 Oct 2023 10:24:15 -0700
Message-ID: <CALs-HssL=wNwj9nRuZwpZhy1CB9p9-X=OqgwBw9zvgA7hA4fEg@mail.gmail.com>
Subject: Re: [PATCH v2 01/19] riscv: hwprobe: factorize hwprobe ISA extension reporting
To:     =?UTF-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= <cleger@rivosinc.com>
Cc:     linux-riscv@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        Palmer Dabbelt <palmer@rivosinc.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Jonathan Corbet <corbet@lwn.net>,
        Andrew Jones <ajones@ventanamicro.com>,
        Conor Dooley <conor@kernel.org>,
        Samuel Ortiz <sameo@rivosinc.com>
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On Tue, Oct 17, 2023 at 6:15=E2=80=AFAM Cl=C3=A9ment L=C3=A9ger <cleger@riv=
osinc.com> wrote:
>
> Factorize ISA extension reporting by using a macro rather than
> copy/pasting extension names. This will allow adding new extensions more
> easily.
>
> Signed-off-by: Cl=C3=A9ment L=C3=A9ger <cleger@rivosinc.com>
> ---
>  arch/riscv/kernel/sys_riscv.c | 32 ++++++++++++++++++--------------
>  1 file changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.=
c
> index 473159b5f303..e207874e686e 100644
> --- a/arch/riscv/kernel/sys_riscv.c
> +++ b/arch/riscv/kernel/sys_riscv.c
> @@ -145,20 +145,24 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *=
pair,
>         for_each_cpu(cpu, cpus) {
>                 struct riscv_isainfo *isainfo =3D &hart_isa[cpu];
>
> -               if (riscv_isa_extension_available(isainfo->isa, ZBA))
> -                       pair->value |=3D RISCV_HWPROBE_EXT_ZBA;
> -               else
> -                       missing |=3D RISCV_HWPROBE_EXT_ZBA;
> -
> -               if (riscv_isa_extension_available(isainfo->isa, ZBB))
> -                       pair->value |=3D RISCV_HWPROBE_EXT_ZBB;
> -               else
> -                       missing |=3D RISCV_HWPROBE_EXT_ZBB;
> -
> -               if (riscv_isa_extension_available(isainfo->isa, ZBS))
> -                       pair->value |=3D RISCV_HWPROBE_EXT_ZBS;
> -               else
> -                       missing |=3D RISCV_HWPROBE_EXT_ZBS;
> +#define CHECK_ISA_EXT(__ext)                                            =
       \
> +               do {                                                     =
       \
> +                       if (riscv_isa_extension_available(isainfo->isa, _=
_ext)) \
> +                               pair->value |=3D RISCV_HWPROBE_EXT_##__ex=
t;       \
> +                       else                                             =
       \
> +                               missing |=3D RISCV_HWPROBE_EXT_##__ext;  =
         \
> +               } while (false)
> +
> +               /*
> +                * Only use CHECK_ISA_EXT() for extensions which can be e=
xposed
> +                * to userspace, regardless of the kernel's configuration=
, as no
> +                * other checks, besides presence in the hart_isa bitmap,=
 are
> +                * made.

This comment alludes to a dangerous trap, but I'm having trouble
understanding what it is. Perhaps some rewording to more explicitly
state the danger would be appropriate. Other than that:

Reviewed-by: Evan Green <evan@rivosinc.com>