linux-kernel - Re: [PATCH v3 2/7] RISC-V: Add a syscall for HW probing

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Message-ID: <Y/0sikPIVR3j7cKI@spud>
Date:   Mon, 27 Feb 2023 22:19:54 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Evan Green <evan@...osinc.com>
Cc:     Palmer Dabbelt <palmer@...osinc.com>, heiko@...ech.de,
        slewis@...osinc.com, vineetg@...osinc.com,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Bresticker <abrestic@...osinc.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Arnd Bergmann <arnd@...db.de>,
        Atish Patra <atishp@...osinc.com>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Celeste Liu <coelacanthus@...look.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Guo Ren <guoren@...nel.org>, Jonathan Corbet <corbet@....net>,
        Niklas Cassel <niklas.cassel@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Ruizhe Pan <c141028@...il.com>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Tobias Klauser <tklauser@...tanz.ch>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 2/7] RISC-V: Add a syscall for HW probing

On Tue, Feb 21, 2023 at 11:08:53AM -0800, Evan Green wrote:
> We don't have enough space for these all in ELF_HWCAP{,2} and there's no
> system call that quite does this, so let's just provide an arch-specific
> one to probe for hardware capabilities.  This currently just provides
> m{arch,imp,vendor}id, but with the key-value pairs we can pass more in
> the future.
> 
> Co-developed-by: Palmer Dabbelt <palmer@...osinc.com>
> Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
> Signed-off-by: Evan Green <evan@...osinc.com>

> +static
> +int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs, long pair_count,
> +		      long cpu_count, unsigned long __user *cpus_user,
> +		      unsigned long flags)

I almost feel bad commenting this, but this is now the only function
split like this w/ the static on its own line.

With the same caveat about ignorance about glibc's desires & lingering
doubt as to whether this interface is the right way to go, this looks
good to me now.
I'm reluctant to give an R-b for the latter reason, but assuming the
Higher Power deem this approach acceptable:
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Cheers,
Conor.

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