linux-kernel - Re: [PATCH 1/2] perf/x86: Disable non generic regs for software/probe events

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Message-ID: <85585e79-612c-f667-dc2a-e4b589d13778@linux.intel.com>
Date:   Mon, 27 May 2019 14:33:09 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     vincent.weaver@...ne.edu, ak@...ux.intel.com, peterz@...radead.org,
        alexander.shishkin@...ux.intel.com, acme@...hat.com,
        jolsa@...hat.com, eranian@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] perf/x86: Disable non generic regs for software/probe
 events



On 5/25/2019 4:48 AM, Ingo Molnar wrote:
> 
> * kan.liang@...ux.intel.com <kan.liang@...ux.intel.com> wrote:
> 
>> @@ -57,6 +57,11 @@ static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
>>   #endif
>>   };
>>   
>> +u64 non_generic_regs_mask(void)
>> +{
>> +	return (~((1ULL << PERF_REG_X86_XMM0) - 1));
>> +}
>> +
>>   u64 perf_reg_value(struct pt_regs *regs, int idx)
>>   {
>>   	struct x86_perf_regs *perf_regs;
>> diff --git a/include/linux/perf_regs.h b/include/linux/perf_regs.h
>> index 4767474..c1c3454 100644
>> --- a/include/linux/perf_regs.h
>> +++ b/include/linux/perf_regs.h
>> @@ -9,6 +9,8 @@ struct perf_regs {
>>   	struct pt_regs	*regs;
>>   };
>>   
>> +u64 non_generic_regs_mask(void);
> 
> This is a *constant* value, why is it in a separate function, not an
> inline?
> 
> Or rather, since it's obviously a constant, name it in such a way.
> (PERF_REG_X86_NON_GENERIC_MASK or so. >
> To the generic code define it as 0 if arch headers haven't overriden it.
>

I will name it PERF_REG_NON_GENERIC_MASK in generic code.

Perf tool also defined a similar macro. I think I will define 
PERF_REG_NON_GENERIC_MASK in X86 uapi header. So both kernel and user 
space can use it.

I will send out V2 to address all comments.

Thanks,
Kan

>> +u64 __weak non_generic_regs_mask(void)
>> +{
>> +	return 0;
>> +}
>> +
>> +static inline bool has_non_generic_regs(struct perf_event *event)
>> +{
>> +	u64 mask = non_generic_regs_mask();
>> +
>> +	return ((event->attr.sample_regs_user & mask) ||
>> +		(event->attr.sample_regs_intr & mask));
> 
> 'return' is not a function ...
> 
>> +	/* only support generic regs */
>> +	if (has_non_generic_regs(event))
>> +		return -EOPNOTSUPP;
> 
> In human readable comments please use complete sentences with no
> unnecessary abbreviations, i.e. "Only support generic registers".
> 
> Thanks,
> 
> 	Ingo
>