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

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Message-ID: <21d9733a-94de-b16d-9bff-583497297a61@redhat.com>
Date:   Thu, 10 Nov 2016 12:09:41 -0600
From:   Wei Huang <wei@...hat.com>
To:     Will Deacon <will.deacon@....com>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        shannon.zhao@...aro.org, kvm@...r.kernel.org,
        christoffer.dall@...aro.org, drjones@...hat.com,
        cov@...eaurora.org, 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 11:17 AM, Will Deacon wrote:
> On Thu, Nov 10, 2016 at 03:32:12PM +0000, Marc Zyngier wrote:
>> 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.
> 
> Yeah, just take the sets that you need (i.e. the architected events).

Hi Will,

Just to clarify what "architected" means:

We need two for KVM: SW_INCR (architectural) and CPU_CYCLES
(micro-architectural). Looking at perf_event.c file, I can either
relocate the  "Required events" (6 events) or the whole set of
ARMV8_PMUV3_PERFCTR_* (~50 events) to perf_event.h. Which way you prefer?

Thanks,
-Wei

> 
> Also, check that it builds.
> 
> Will
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