linux-kernel - Re: [PATCH] arm_pmu: Delete incorrect cache event mapping for some armv8_pmuv3 events.

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Message-ID: <b04c43bd-5c90-cc06-e2cc-ce542981853a@huawei.com>
Date:   Fri, 5 Oct 2018 13:27:08 +0100
From:   John Garry <john.garry@...wei.com>
To:     Will Deacon <will.deacon@....com>,
        Ganapatrao Kulkarni <gklkml16@...il.com>
CC:     Mark Rutland <mark.rutland@....com>,
        "Nair, Jayachandran" <Jayachandran.Nair@...ium.com>,
        <Jan.Glauber@...ium.com>, Peter Zijlstra <peterz@...radead.org>,
        <catalin.marinas@....com>, LKML <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Robert Richter <Robert.Richter@...ium.com>,
        Ingo Molnar <mingo@...hat.com>, <Vadim.Lomovtsev@...ium.com>,
        Ganapatrao Kulkarni <Ganapatrao.Kulkarni@...ium.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] arm_pmu: Delete incorrect cache event mapping for some
 armv8_pmuv3 events.

On 04/10/2018 13:22, Will Deacon wrote:
> Hi Ganapat,
>
> On Thu, Oct 04, 2018 at 11:12:09AM +0530, Ganapatrao Kulkarni wrote:
>> can you please pull this patch?
>
> I still don't like the idea of just removing events like this, especially
> when other architectures (including some x86 and Power CPUs afaict) playa
> similar games for generic events, and these events do actually appear in
> user code.
>
> I also don't understand why you remove the TLB events. I think that logic
> would imply we should remove all of the events, because we can't distinguish
> prefetches from reads either. If we want to be consistent, then I think
> we should just remove the OP_WRITE events for L1D and BPU -- would you be
> ok with that instead?
>
> Also, looking at the code, I think our PMCEID parsing is broken for 8.1
> parts, where the upper 32 bits of the register are offset by 0x4000 in the
> event numbering space.
>

Here's something I noticed:
static ssize_t
armv8pmu_events_sysfs_show(struct device *dev,
			   struct device_attribute *attr, char *page)
{
	struct perf_pmu_events_attr *pmu_attr;

	pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr);

	return sprintf(page, "event=0x%03llx\n", pmu_attr->id);

Should this be min width now be 4, since event width is now 16 bits 
(even though I don't know why we need to specify this width at all)?

Cheers,
John

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

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