linux-kernel - Re: [PATCH 1/2] arm64: perf: Move ARMv8 PMU perf event definitions to asm/perf

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Message-ID: <733f067d-7f3b-df28-eab7-a15abba947fc@arm.com>
Date:   Thu, 10 Nov 2016 15:32:12 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Wei Huang <wei@...hat.com>, kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org, shannon.zhao@...aro.org,
        kvm@...r.kernel.org, christoffer.dall@...aro.org,
        drjones@...hat.com, cov@...eaurora.org, will.deacon@....com,
        mark.rutland@....com, catalin.marinas@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] arm64: perf: Move ARMv8 PMU perf event definitions to
 asm/perf_event.h

On 10/11/16 15:12, Wei Huang wrote:
> 
> 
> On 11/10/2016 03:10 AM, Marc Zyngier wrote:
>> Hi Wei,
>>
>> On 09/11/16 19:57, Wei Huang wrote:
>>> This patch moves ARMv8-related perf event definitions from perf_event.c
>>> to asm/perf_event.h; so KVM code can use them directly. This also help
>>> remove a duplicated definition of SW_INCR in perf_event.h.
>>>
>>> Signed-off-by: Wei Huang <wei@...hat.com>
>>> ---
>>>  arch/arm64/include/asm/perf_event.h | 161 +++++++++++++++++++++++++++++++++++-
>>>  arch/arm64/kernel/perf_event.c      | 161 ------------------------------------
>>>  2 files changed, 160 insertions(+), 162 deletions(-)
>>>
>>> diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h
>>> index 2065f46..6c7b18b 100644
>>> --- a/arch/arm64/include/asm/perf_event.h
>>> +++ b/arch/arm64/include/asm/perf_event.h
>>> @@ -46,7 +46,166 @@
>>>  #define	ARMV8_PMU_EVTYPE_MASK	0xc800ffff	/* Mask for writable bits */
>>>  #define	ARMV8_PMU_EVTYPE_EVENT	0xffff		/* Mask for EVENT bits */
>>>  
>>> -#define ARMV8_PMU_EVTYPE_EVENT_SW_INCR	0	/* Software increment event */
>>> +/*
>>> + * ARMv8 PMUv3 Performance Events handling code.
>>> + * Common event types.
>>> + */
>>> +
>>> +/* Required events. */
>>> +#define ARMV8_PMUV3_PERFCTR_SW_INCR				0x00
>>> +#define ARMV8_PMUV3_PERFCTR_L1D_CACHE_REFILL			0x03
>>> +#define ARMV8_PMUV3_PERFCTR_L1D_CACHE				0x04
>>> +#define ARMV8_PMUV3_PERFCTR_BR_MIS_PRED				0x10
>>> +#define ARMV8_PMUV3_PERFCTR_CPU_CYCLES				0x11
>>> +#define ARMV8_PMUV3_PERFCTR_BR_PRED				0x12
>>
>> In my initial review, I asked for the "required" events to be moved to a
>> shared location. What's the rational for moving absolutely everything?
> 
> I did notice the phrase "required" in the original email. However I
> think it is weird to have two places for a same set of PMU definitions.
> Other developers might think these two are missing if they don't search
> kernel files carefully.
> 
> If Will Deacon and you insist, I can move only two defs to perf_event.h,
> consolidated with the 2nd patch into a single one.

My personal feeling is that only architected events should be in a
public header. The CPU-specific ones are probably better kept private,
as it is doubtful that other users would appear).

I'll leave it up to Will to decide, as all I want to avoid is the
duplication of constants between the PMU and KVM code bases.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...