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Date:   Thu, 01 Dec 2022 11:21:51 -0800 (PST)
Subject:     Re: [PATCH] Documentation: riscv: note that counter access is part of the uABI
In-Reply-To: <20221201135110.3855965-1-conor.dooley@microchip.com>
CC:     corbet@lwn.net, Conor Dooley <conor.dooley@microchip.com>,
        linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     Conor Dooley <conor.dooley@microchip.com>
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On Thu, 01 Dec 2022 05:51:10 PST (-0800), Conor Dooley wrote:
> Commit 5a5294fbe020 ("RISC-V: Re-enable counter access from userspace")
> fixed userspace access to CYCLE, TIME & INSTRET counters and left a nice
> comment in-place about why they must not be restricted. Since we now
> have a uABI doc in RISC-V land, add a section documenting it.
>
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
> Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
> it to be applicable, just getting a patch into patchwork while I don't
> forget about this.
> ---
>  Documentation/riscv/uabi.rst | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/riscv/uabi.rst b/Documentation/riscv/uabi.rst
> index 8d2651e42fda..638ddce56700 100644
> --- a/Documentation/riscv/uabi.rst
> +++ b/Documentation/riscv/uabi.rst
> @@ -3,6 +3,13 @@
>  RISC-V Linux User ABI
>  =====================
>
> +Counter access
> +--------------
> +
> +Access to the CYCLE, TIME and INSTRET counters, now controlled by the SBI PMU
> +extension, were part of the ISA when the uABI was frozen & so remain accessible
> +from userspace.
> +
>  ISA string ordering in /proc/cpuinfo
>  ------------------------------------
>
>
> base-commit: 13ee7ef407cfcf63f4f047460ac5bb6ba5a3447d
> prerequisite-patch-id: d17a9ffb6fcf99eb683728da98cd50e18cd28fe8
> prerequisite-patch-id: 0df4127e3f4a0c02a235fea00bcb69cd94fabb38
> prerequisite-patch-id: 171724b870ba212b714ebbded480269accd83733

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

I think I merged the last one of these, but if the doc folks pick it up 
that's fine with me.  Otherwise I'll take it when it comes back around, 
so folks have time to take a look.