linux-kernel - Re: [PATCH 7/8] x86/intel_rdt: schemata file support for MBA prepare\

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Message-ID: <alpine.DEB.2.10.1703301205080.25705@vshiva-Udesk>
Date:   Thu, 30 Mar 2017 12:05:49 -0700 (PDT)
From:   Shivappa Vikas <vikas.shivappa@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
cc:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        vikas.shivappa@...el.com, linux-kernel@...r.kernel.org,
        x86@...nel.org, hpa@...or.com, mingo@...nel.org,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        tony.luck@...el.com, fenghua.yu@...el.com, andi.kleen@...el.com
Subject: Re: [PATCH 7/8] x86/intel_rdt: schemata file support for MBA
 prepare\



On Wed, 1 Mar 2017, Thomas Gleixner wrote:

> On Fri, 17 Feb 2017, Vikas Shivappa wrote:
>
> Subject: x86/intel_rdt: schemata file support for MBA prepare
>
> I have no idea what MBA prepare is. Is that yet another variant aside of
> MBE?
>
>> Add support to introduce generic APIs for control validation and writing
>> QOS_MSRs for RDT resources. The control validation api is meant to
>> validate the control values like cache bit mask for CAT and memory b/w
>> percentage for MBA. A resource generic display format is also added and
>> used for the resources depending on whether its displayed in
>> hex/decimal.
>
> The usual unpenetratable mess of random sentences lumped together.
>
>> diff --git a/arch/x86/include/asm/intel_rdt.h b/arch/x86/include/asm/intel_rdt.h
>> index 24de64c..8748b0d 100644
>> --- a/arch/x86/include/asm/intel_rdt.h
>> +++ b/arch/x86/include/asm/intel_rdt.h
>> @@ -77,6 +77,9 @@ struct rftype {
>>   * @default_ctrl:		Specifies default cache cbm or mem b/w percent.
>>   * @min_cbm_bits:		Minimum number of consecutive bits to be set
>>   *				in a cache bit mask
>> + * @format_str:		Per resource format string to show domain val
>
> Can you please spell out words in comments instead of using random
> abbreviations just as you see fit?
>
>> + * @parse_ctrlval:		Per resource API to parse the ctrl values
>
> That's not an API. That's a function pointer.
>
>> + * @msr_update:		API to update QOS MSRs
>
> Ditto.
>
>>   * @info_files:		resctrl info files for the resource
>>   * @infofiles_len:		Number of info files
>>   * @max_delay:			Max throttle delay. Delay is the hardware
>> @@ -105,6 +108,9 @@ struct rdt_resource {
>>  	int			cbm_len;
>>  	int			min_cbm_bits;
>>  	u32			default_ctrl;
>> +	const char		*format_str;
>> +	int (*parse_ctrlval)	(char *buf, struct rdt_resource *r);
>> +	void (*msr_update)	(void *a1, void *a2, struct rdt_resource *r);
>
> void *a1, *a2? Dammit, both implementations (CAT and MBA) use the same
> types. This just avoids type safety which does not magically come back by
> your completely nonsensical typecasts inside the callback implementations.
>
>> +void cqm_wrmsr(void *a1, void *a2, struct rdt_resource *r)
>
> And this is global because it's only used in this file, right?
>
>> +{
>> +	struct rdt_domain *d = (struct rdt_domain *)a2;
>> +	struct msr_param *m = (struct msr_param *)a1;
>
> Oh well......
>
>> +	int i;
>> +
>> +	for (i = m->low; i < m->high; i++) {
>> +		int idx = cbm_idx(r, i);
>> +
>> +		wrmsrl(r->msr_base + idx, d->ctrl_val[i]);
>> +	}
>> +}
>
>> -static bool cbm_validate(unsigned long var, struct rdt_resource *r)
>> +static int cbm_validate(char *buf, unsigned long *data, struct rdt_resource *r)
>>  {
>> -	unsigned long first_bit, zero_bit;
>> +	unsigned long first_bit, zero_bit, var;
>> +	int ret;
>> +
>> +	ret = kstrtoul(buf, 16, &var);
>> +	if (ret)
>> +		return ret;
>>
>>  	if (var == 0 || var > r->default_ctrl)
>> -		return false;
>> +		return -EINVAL;
>
> So you change this function and the whole call chain to return either
> -EINVAL or 0 instead of false/true.
>
> And then you treat the integer return value as boolean on the call site
> again:

Will fix wrt all the comments.

Thanks,
Vikas