linux-kernel - Re: [PATCH v3 08/10] Documentation: admin-guide: Add riscv sysctl_perf_user

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Message-ID: <20230630-f714cc46ee65cc65318f2ada@orel>
Date:   Fri, 30 Jun 2023 13:16:41 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Alexandre Ghiti <alexghiti@...osinc.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        Will Deacon <will@...nel.org>, Rob Herring <robh@...nel.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 08/10] Documentation: admin-guide: Add riscv
 sysctl_perf_user_access

On Fri, Jun 30, 2023 at 10:30:11AM +0200, Alexandre Ghiti wrote:
> riscv now uses this sysctl so document its usage for this architecture.
> 
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> ---
>  Documentation/admin-guide/sysctl/kernel.rst | 26 +++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
> index d85d90f5d000..c376692b372b 100644
> --- a/Documentation/admin-guide/sysctl/kernel.rst
> +++ b/Documentation/admin-guide/sysctl/kernel.rst
> @@ -941,16 +941,34 @@ enabled, otherwise writing to this file will return ``-EBUSY``.
>  The default value is 8.
>  
>  
> -perf_user_access (arm64 only)
> -=================================
> +perf_user_access (arm64 and riscv only)
> +=======================================
> +
> +Controls user space access for reading perf event counters.
>  
> -Controls user space access for reading perf event counters. When set to 1,
> -user space can read performance monitor counter registers directly.
> +arm64
> +=====
>  
>  The default value is 0 (access disabled).

Should add a blank line here.

> +When set to 1, user space can read performance monitor counter registers
> +directly.
>  
>  See Documentation/arm64/perf.rst for more information.
>  
> +riscv
> +=====
> +
> +When set to 0, user access is disabled.
> +
> +When set to 1, user space can read performance monitor counter registers
> +directly only through perf, any direct access without perf intervention will

Remove 'directly only'

(It can't be both "direct" and "through" at the same time.)

> +trigger an illegal instruction.
> +
> +The default value is 2,

This is no longer true.

> which enables legacy mode (user space has direct
> +access to cycle and insret CSRs only). Note that this legacy value
> +is deprecated and will be removed once all userspace applications are fixed.
> +
> +Note that the time CSR is for now always accessible to all modes.

s/always accessible/always directly accessible/

Also, remove 'for now'. While we may change this in the future, I'm not
sure if the 'for now' helps much. Maybe a "This may change in the future."
type of sentence? Or, just nothing (for now :-) and we'll modify this
document if it changes later.

Thanks,
drew

>  
>  pid_max
>  =======
> -- 
> 2.39.2
>