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From:   Alexandre Ghiti <alexghiti@rivosinc.com>
Date:   Mon, 3 Jul 2023 11:45:00 +0200
Message-ID: <CAHVXubh97QyXbiQ6wcaEOkPBKJwzCzm77FgQ+eHEYFFEQyToJw@mail.gmail.com>
Subject: Re: [PATCH v3 08/10] Documentation: admin-guide: Add riscv sysctl_perf_user_access
To:     Andrew Jones <ajones@ventanamicro.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Ian Rogers <irogers@google.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Atish Patra <atishp@atishpatra.org>,
        Anup Patel <anup@brainfault.org>,
        Will Deacon <will@kernel.org>, Rob Herring <robh@kernel.org>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org, linux-riscv@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org
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On Fri, Jun 30, 2023 at 1:16=E2=80=AFPM Andrew Jones <ajones@ventanamicro.c=
om> wrote:
>
> 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@rivosinc.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/Documentatio=
n/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 retu=
rn ``-EBUSY``.
> >  The default value is 8.
> >
> >
> > -perf_user_access (arm64 only)
> > -=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > +perf_user_access (arm64 and riscv only)
> > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > +
> > +Controls user space access for reading perf event counters.
> >
> > -Controls user space access for reading perf event counters. When set t=
o 1,
> > -user space can read performance monitor counter registers directly.
> > +arm64
> > +=3D=3D=3D=3D=3D
> >
> >  The default value is 0 (access disabled).
>
> Should add a blank line here.

Done, thanks

>
> > +When set to 1, user space can read performance monitor counter registe=
rs
> > +directly.
> >
> >  See Documentation/arm64/perf.rst for more information.
> >
> > +riscv
> > +=3D=3D=3D=3D=3D
> > +
> > +When set to 0, user access is disabled.
> > +
> > +When set to 1, user space can read performance monitor counter registe=
rs
> > +directly only through perf, any direct access without perf interventio=
n 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.

Damn, sorry about that.

>
> > 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.

I won't say anything about the future, thanks!

I also harmonized the "user space" and "userspace" in this document
with what arm64 does.

Thanks

>
> Thanks,
> drew
>
> >
> >  pid_max
> >  =3D=3D=3D=3D=3D=3D=3D
> > --
> > 2.39.2
> >