linux-kernel - Re: [PATCH v11 8/8] perf: ARM DynamIQ Shared Unit PMU support

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Message-ID: <20180223113552.2gn27h4uxbpo5zoq@lakrids.cambridge.arm.com>
Date:   Fri, 23 Feb 2018 11:35:52 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Saravana Kannan <skannan@...eaurora.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>, will.deacon@....com,
        robh@...nel.org, sudeep.holla@....com, mathieu.poirier@...aro.org,
        peterz@...radead.org, jonathan.cameron@...wei.com,
        linux-kernel@...r.kernel.org, marc.zyngier@....com,
        leo.yan@...aro.org, frowand.list@...il.com,
        linux-arm-kernel@...ts.infradead.org, avilaj@...eaurora.org
Subject: Re: [PATCH v11 8/8] perf: ARM DynamIQ Shared Unit PMU support

On Thu, Feb 22, 2018 at 12:38:39PM -0800, Saravana Kannan wrote:
> On 02/22/2018 03:33 AM, Mark Rutland wrote:
> > On Wed, Feb 21, 2018 at 06:32:46PM -0800, Saravana Kannan wrote:
> > > I'm not exactly sure if we can add entries to perf_type_id. If that's
> > > allowed maybe we need to add something line PERF_TYPE_DSU and use that?
> > > 
> > > Or if that's not allowed then would it be better to offset the DSU PMU
> > > events by some number (say 0x1000) and then delete the event type check or
> > > pass PERF_TYPE_RAW to perf_pmu_register()?
> > 
> > As above, neither of these should be necessary.
> 
> For the userspace interface. How about the kernel interface though?
> perf_event_create_kernel_counter() takes attr.type as an input. But there's
> no way to look up the DSU PMU's "type".

There is no lookup mechanism currently.

I take it you want to use DSU events from a kernel module?

It would be possible to have a simlar name -> type lookup mechanism
kernel-side, if necessary.

Thanks,
Mark.