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From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Rob Herring <robh@kernel.org>
Cc: Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Vince Weaver <vincent.weaver@maine.edu>,
	Jonathan Corbet <corbet@lwn.net>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-perf-users@vger.kernel.org,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH v13 3/5] arm64: perf: Add userspace counter access disable switch
Date: Tue, 28 Dec 2021 12:07:02 +0100	[thread overview]
Message-ID: <CAMuHMdVcDxR9sGzc5pcnORiotonERBgc6dsXZXMd6wTvLGA9iw@mail.gmail.com> (raw)
In-Reply-To: <20211208201124.310740-4-robh@kernel.org>

Hi Rob,

On Wed, Dec 8, 2021 at 9:19 PM Rob Herring <robh@kernel.org> wrote:
> Like x86, some users may want to disable userspace PMU counter
> altogether. Add a sysctl 'perf_user_access' file to control userspace
> counter access. The default is '0' which is disabled. Writing '1'
> enables access.
>
> Note that x86 supports globally enabling user access by writing '2' to
> /sys/bus/event_source/devices/cpu/rdpmc. As there's not existing
> userspace support to worry about, this shouldn't be necessary for Arm.
> It could be added later if the need arises.

Thanks for your patch, which is now commit e2012600810c9ded ("arm64:
perf: Add userspace counter access disable switch") in arm64/for-next/core.

This is causing two issues on Renesas Salvator-XS with R-Car H3.
One during kernel boot:

     hw perfevents: enabled with armv8_cortex_a53 PMU driver, 7
counters available
    +sysctl duplicate entry: /kernel//perf_user_access
    +CPU: 0 PID: 1 Comm: swapper/0 Not tainted
5.16.0-rc3-arm64-renesas-00003-ge2012600810c #1420
    +Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
    +Call trace:
    + dump_backtrace+0x0/0x190
    + show_stack+0x14/0x20
    + dump_stack_lvl+0x88/0xb0
    + dump_stack+0x14/0x2c
    + __register_sysctl_table+0x384/0x818
    + register_sysctl+0x20/0x28
    + armv8_pmu_init.constprop.0+0x118/0x150
    + armv8_a57_pmu_init+0x1c/0x28
    + arm_pmu_device_probe+0x1b4/0x558
    + armv8_pmu_device_probe+0x18/0x20
    + platform_probe+0x64/0xd0
    + really_probe+0xb4/0x2f8
    + __driver_probe_device+0x74/0xd8
    + driver_probe_device+0x3c/0xe0
    + __driver_attach+0x80/0x110
    + bus_for_each_dev+0x6c/0xc0
    + driver_attach+0x20/0x28
    + bus_add_driver+0x138/0x1e0
    + driver_register+0x60/0x110
    + __platform_driver_register+0x24/0x30
    + armv8_pmu_driver_init+0x18/0x20
    + do_one_initcall+0x15c/0x31c
    + kernel_init_freeable+0x2f0/0x354
    + kernel_init+0x20/0x120
    + ret_from_fork+0x10/0x20
     hw perfevents: enabled with armv8_cortex_a57 PMU driver, 7
counters available

Presumably the same entry is added twice, once for the A53 PMU,
and a second time for the A57 PMU?

A second during systemd startup:

    systemd-journald[326]: Failed to open runtime journal: No such
file or directory
    systemd-journald[345]: File
/run/log/journal/09223238c0464b38ad4fc1d505d98e17/system.journal
corrupted or uncleanly shut down, renaming and replacing.

followed by lots of

    systemd[<n>]: <foo>.service: Failed to connect stdout to the
journal socket, ignoring: Connection refused

failures.

> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -286,6 +286,8 @@ static const struct attribute_group armv8_pmuv3_events_attr_group = {
>  PMU_FORMAT_ATTR(event, "config:0-15");
>  PMU_FORMAT_ATTR(long, "config1:0");
>
> +static int sysctl_perf_user_access __read_mostly;
> +
>  static inline bool armv8pmu_event_is_64bit(struct perf_event *event)
>  {
>         return event->attr.config1 & 0x1;
> @@ -1104,6 +1106,19 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu)
>         return probe.present ? 0 : -ENODEV;
>  }
>
> +static struct ctl_table armv8_pmu_sysctl_table[] = {
> +       {
> +               .procname       = "perf_user_access",
> +               .data           = &sysctl_perf_user_access,
> +               .maxlen         = sizeof(unsigned int),
> +               .mode           = 0644,
> +               .proc_handler   = proc_dointvec_minmax,
> +               .extra1         = SYSCTL_ZERO,
> +               .extra2         = SYSCTL_ONE,
> +       },
> +       { }
> +};
> +
>  static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
>                           int (*map_event)(struct perf_event *event),
>                           const struct attribute_group *events,
> @@ -1136,6 +1151,8 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
>         cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_CAPS] = caps ?
>                         caps : &armv8_pmuv3_caps_attr_group;
>
> +       register_sysctl("kernel", armv8_pmu_sysctl_table);
> +
>         return 0;
>  }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

WARNING: multiple messages have this Message-ID
From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Rob Herring <robh@kernel.org>
Cc: Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	 Peter Zijlstra <peterz@infradead.org>,
	Vince Weaver <vincent.weaver@maine.edu>,
	Jonathan Corbet <corbet@lwn.net>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Ingo Molnar <mingo@redhat.com>,
	 Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	 Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	 Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	 "the arch/x86 maintainers" <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	 Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-perf-users@vger.kernel.org,
	 Linux-Renesas <linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH v13 3/5] arm64: perf: Add userspace counter access disable switch
Date: Tue, 28 Dec 2021 12:07:02 +0100	[thread overview]
Message-ID: <CAMuHMdVcDxR9sGzc5pcnORiotonERBgc6dsXZXMd6wTvLGA9iw@mail.gmail.com> (raw)
In-Reply-To: <20211208201124.310740-4-robh@kernel.org>

Hi Rob,

On Wed, Dec 8, 2021 at 9:19 PM Rob Herring <robh@kernel.org> wrote:
> Like x86, some users may want to disable userspace PMU counter
> altogether. Add a sysctl 'perf_user_access' file to control userspace
> counter access. The default is '0' which is disabled. Writing '1'
> enables access.
>
> Note that x86 supports globally enabling user access by writing '2' to
> /sys/bus/event_source/devices/cpu/rdpmc. As there's not existing
> userspace support to worry about, this shouldn't be necessary for Arm.
> It could be added later if the need arises.

Thanks for your patch, which is now commit e2012600810c9ded ("arm64:
perf: Add userspace counter access disable switch") in arm64/for-next/core.

This is causing two issues on Renesas Salvator-XS with R-Car H3.
One during kernel boot:

     hw perfevents: enabled with armv8_cortex_a53 PMU driver, 7
counters available
    +sysctl duplicate entry: /kernel//perf_user_access
    +CPU: 0 PID: 1 Comm: swapper/0 Not tainted
5.16.0-rc3-arm64-renesas-00003-ge2012600810c #1420
    +Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
    +Call trace:
    + dump_backtrace+0x0/0x190
    + show_stack+0x14/0x20
    + dump_stack_lvl+0x88/0xb0
    + dump_stack+0x14/0x2c
    + __register_sysctl_table+0x384/0x818
    + register_sysctl+0x20/0x28
    + armv8_pmu_init.constprop.0+0x118/0x150
    + armv8_a57_pmu_init+0x1c/0x28
    + arm_pmu_device_probe+0x1b4/0x558
    + armv8_pmu_device_probe+0x18/0x20
    + platform_probe+0x64/0xd0
    + really_probe+0xb4/0x2f8
    + __driver_probe_device+0x74/0xd8
    + driver_probe_device+0x3c/0xe0
    + __driver_attach+0x80/0x110
    + bus_for_each_dev+0x6c/0xc0
    + driver_attach+0x20/0x28
    + bus_add_driver+0x138/0x1e0
    + driver_register+0x60/0x110
    + __platform_driver_register+0x24/0x30
    + armv8_pmu_driver_init+0x18/0x20
    + do_one_initcall+0x15c/0x31c
    + kernel_init_freeable+0x2f0/0x354
    + kernel_init+0x20/0x120
    + ret_from_fork+0x10/0x20
     hw perfevents: enabled with armv8_cortex_a57 PMU driver, 7
counters available

Presumably the same entry is added twice, once for the A53 PMU,
and a second time for the A57 PMU?

A second during systemd startup:

    systemd-journald[326]: Failed to open runtime journal: No such
file or directory
    systemd-journald[345]: File
/run/log/journal/09223238c0464b38ad4fc1d505d98e17/system.journal
corrupted or uncleanly shut down, renaming and replacing.

followed by lots of

    systemd[<n>]: <foo>.service: Failed to connect stdout to the
journal socket, ignoring: Connection refused

failures.

> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -286,6 +286,8 @@ static const struct attribute_group armv8_pmuv3_events_attr_group = {
>  PMU_FORMAT_ATTR(event, "config:0-15");
>  PMU_FORMAT_ATTR(long, "config1:0");
>
> +static int sysctl_perf_user_access __read_mostly;
> +
>  static inline bool armv8pmu_event_is_64bit(struct perf_event *event)
>  {
>         return event->attr.config1 & 0x1;
> @@ -1104,6 +1106,19 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu)
>         return probe.present ? 0 : -ENODEV;
>  }
>
> +static struct ctl_table armv8_pmu_sysctl_table[] = {
> +       {
> +               .procname       = "perf_user_access",
> +               .data           = &sysctl_perf_user_access,
> +               .maxlen         = sizeof(unsigned int),
> +               .mode           = 0644,
> +               .proc_handler   = proc_dointvec_minmax,
> +               .extra1         = SYSCTL_ZERO,
> +               .extra2         = SYSCTL_ONE,
> +       },
> +       { }
> +};
> +
>  static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
>                           int (*map_event)(struct perf_event *event),
>                           const struct attribute_group *events,
> @@ -1136,6 +1151,8 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
>         cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_CAPS] = caps ?
>                         caps : &armv8_pmuv3_caps_attr_group;
>
> +       register_sysctl("kernel", armv8_pmu_sysctl_table);
> +
>         return 0;
>  }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-12-28 11:07 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-08 20:11 [PATCH v13 0/5] arm64 userspace counter support Rob Herring
2021-12-08 20:11 ` Rob Herring
2021-12-08 20:11 ` [PATCH v13 1/5] x86: perf: Move RDPMC event flag to a common definition Rob Herring
2021-12-08 20:11   ` Rob Herring
2021-12-08 20:11 ` [PATCH v13 2/5] perf: Add a counter for number of user access events in context Rob Herring
2021-12-08 20:11   ` Rob Herring
2021-12-08 20:11 ` [PATCH v13 3/5] arm64: perf: Add userspace counter access disable switch Rob Herring
2021-12-08 20:11   ` Rob Herring
2021-12-28 11:07   ` Geert Uytterhoeven [this message]
2021-12-28 11:07     ` Geert Uytterhoeven
2022-01-04 13:56     ` Will Deacon
2022-01-04 13:56       ` Will Deacon
2022-01-05 11:25       ` Will Deacon
2022-01-05 11:25         ` Will Deacon
2022-01-07 10:22       ` Geert Uytterhoeven
2022-01-07 10:22         ` Geert Uytterhoeven
2021-12-08 20:11 ` [PATCH v13 4/5] arm64: perf: Enable PMU counter userspace access for perf event Rob Herring
2021-12-08 20:11   ` Rob Herring
2021-12-08 20:11 ` [PATCH v13 5/5] Documentation: arm64: Document PMU counters access from userspace Rob Herring
2021-12-08 20:11   ` Rob Herring
2021-12-14 14:04 ` [PATCH v13 0/5] arm64 userspace counter support Will Deacon
2021-12-14 14:04   ` Will Deacon

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