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

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Message-ID: <d9ef10b9-44f2-b02e-9d90-02cf348aa49c@redhat.com>
Date:   Thu, 10 Nov 2016 09:12:35 -0600
From:   Wei Huang <wei@...hat.com>
To:     Marc Zyngier <marc.zyngier@....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 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.

> KVM only needs to know about ARMV8_PMUV3_PERFCTR_SW_INCR and
> ARMV8_PMUV3_PERFCTR_CPU_CYCLES, so I thought that moving the above six
> events (and maybe the following two) would be enough.
> 
> Also, you've now broken the build by dropping
> ARMV8_PMU_EVTYPE_EVENT_SW_INCR without amending it use in the KVM PMU
> code (see the kbuild report).
> 

My bad. I tested compilation only after two patches applied. Will fix it.

<snip>

>> +
>>  /* PMUv3 HW events mapping. */
>>  
>>  /*
>>
> 
> Thanks,
> 
> 	M.
>