linux-kernel - Re: [PATCH] perf/core: move all of the pmu devices into their own location

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Message-ID: <2025020444-chivalry-wanting-7f0c@gregkh>
Date: Tue, 4 Feb 2025 08:05:53 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Ian Rogers <irogers@...gle.com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH] perf/core: move all of the pmu devices into their own
 location

On Mon, Feb 03, 2025 at 11:44:13AM -0800, Ian Rogers wrote:
> On Mon, Feb 3, 2025 at 11:25 AM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > In sysfs, for some reason, all pmu devices seem to show up in the "root"
> > of /sys/devices/ making for a confusing mess as these devices are not
> > really at the root of the system at all.
> >
> > Create a fake root devices, "pmu_bus" and place them all under there if
> > they do not already have a parent device set, cleaning up sysfs to look
> > more sane.
> >
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> > Cc: Jiri Olsa <jolsa@...nel.org>
> > Cc: Ian Rogers <irogers@...gle.com>
> > Cc: Adrian Hunter <adrian.hunter@...el.com>
> > Cc: "Liang, Kan" <kan.liang@...ux.intel.com>
> > Cc: linux-perf-users@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >
> > Note, if you all don't like "pmu_bus" for the name, that's fine, please
> > let me know and I can rename it to something else, but it should be
> > something to get these objects out of the root sysfs directory.
> 
> Excuse my ignorance, does the event_source bus already provide a
> similar solution?
> ```
> $ ls /sys/bus/event_source/devices
> breakpoint   i915       msr         uncore_arb     uncore_cbox_3
> uncore_cbox_7              uprobe
> cpu          intel_bts  power       uncore_cbox_0  uncore_cbox_4  uncore_clock
> cstate_core  intel_pt   software    uncore_cbox_1  uncore_cbox_5
> uncore_imc_free_running_0
> cstate_pkg   kprobe     tracepoint  uncore_cbox_2  uncore_cbox_6
> uncore_imc_free_running_1
> $ ls /sys/devices
> breakpoint   intel_pt     platform    uncore_arb     uncore_cbox_5
>          uprobe
> cpu          isa          pnp0        uncore_cbox_0  uncore_cbox_6
>          virtual
> cstate_core  kprobe       power       uncore_cbox_1  uncore_cbox_7
> cstate_pkg   LNXSYSTM:00  software    uncore_cbox_2  uncore_clock
> i915         msr          system      uncore_cbox_3  uncore_imc_free_running_0
> intel_bts    pci0000:00   tracepoint  uncore_cbox_4  uncore_imc_free_running_1
> ```

Those are the exact same device structures :)

Look at /sys/bus/event_source/devices/ those are symlinks back to
/sys/devices.  In other words, that's the exact same structures, and
the mess in /sys/devices/ with these event devices is what I am trying
to clean up.

thanks,

greg k-h