[PATCH v3 1/3] arm64: perf: Add support caps in sysfs
Shaokun Zhang
zhangshaokun at hisilicon.com
Mon Jul 20 09:11:04 EDT 2020
Hi Will,
在 2020/7/20 18:54, Will Deacon 写道:
> On Mon, Jul 20, 2020 at 11:50:19AM +0100, Mark Rutland wrote:
>> On Mon, Jul 20, 2020 at 11:15:19AM +0100, Will Deacon wrote:
>>> On Thu, Jun 18, 2020 at 09:35:42PM +0800, Shaokun Zhang wrote:
>>
>>>> +static umode_t
>>>> +armv8pmu_caps_attr_is_visible(struct kobject *kobj, struct attribute *attr,
>>>> + int unused)
>>>> +{
>>>> + int pmuver = armv8pmu_get_pmu_version();
>>>> +
>>>> + if (pmuver >= ID_AA64DFR0_PMUVER_8_4)
>>>> + return attr->mode;
>>>
>>> Is this sufficient? I'm a bit confused by the text in the Arm ARM that says:
>>>
>>> | If ARMv8.4-PMU is implemented:
>>> | * If STALL_SLOT is not implemented, it is IMPLEMENTATION DEFINED whether
>>> | the PMMIR System registers are implemented.
>>> | * If STALL_SLOT is implemented, then the PMMIR System registers are
>>> | implemented.
>>>
>>> whereas the register description for PMMIR_EL1 says:
>>>
>>> | This register is present only when ARMv8.4-PMU is implemented.
>>
>> I think this is trying to say that when ARMv8.4-PMU is not implemented,
>> PMMIR definitely isn't implemented (i.e. the the presence of PMMIR_EL1
>> implies the presence of ARMv8.4-PMU).
>>
>>> Mark -- please could you clarify whether or not we need to check STALL_SLOT
>>> as well as the PMUVer?
>>
>> Given the explciit wording that it's IMP DEF, I suspect that we need to
>> check both.
>>
>> I'll go chase this up.
>
> Thanks. In the meantime, Shaokun, can you send updated versions of the first
> two patches, please? We'll play it safe and check STALL_SLOT as well pending
Ok, I will submit them soon addressed your other comments together.
Thanks,
Shaokun
> Mark's findings.
>
> Will
>
> .
>
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