linux-kernel - Re: [PATCH V3 01/23] perf/x86: Support outputting XMM registers

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Message-ID: <f1fc3d9d-259d-85e7-c85a-949e56bdc631@linux.intel.com>
Date:   Tue, 26 Mar 2019 09:55:00 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     peterz@...radead.org, acme@...nel.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V3 01/23] perf/x86: Support outputting XMM registers



On 3/26/2019 9:47 AM, Thomas Gleixner wrote:
> On Tue, 26 Mar 2019, Liang, Kan wrote:
>> On 3/25/2019 8:11 PM, Thomas Gleixner wrote:
>>
>> -#define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
>> +#define REG_RESERVED	0
>
> What's the point of having this around?

I once thought it may be kept for future extension if we have more regs.
But, yes, we should remove it completely for now.

Thanks,
Kan

> 
>>   int perf_reg_validate(u64 mask)
>>   {
>>   	if (!mask || mask & REG_RESERVED)
>>   		return -EINVAL;
> 
>   mask & 0 == 0, right? So which bits are you checking here?
> 
> Thanks,
> 
> 	tglx
>