linux-kernel - Re: [PATCH 4/5] x86/intel_rdt: Reset the cbm MSR during rmdir

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Date:   Thu, 9 Mar 2017 17:45:13 -0800 (PST)
From:   Shivappa Vikas <vikas.shivappa@...ux.intel.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 4/5] x86/intel_rdt: Reset the cbm MSR during rmdir



On Wed, 1 Mar 2017, Thomas Gleixner wrote:

> On Fri, 17 Feb 2017, Vikas Shivappa wrote:
>
>> During rmdir reset the ctrl values to all 1s in the QOS_MSR for the
>> directory's closid. This is done so that that next time when the closid
>> is reused they dont reflect old values.
>
> Sigh.
>
>> +static int reset_all_ctrls(struct rdt_resource *r, u32 sclosid, u32 eclosid)
>
> What's so wrong with using 'start' and 'end' instead of these cryptic names?
>
>>  {
>>  	struct msr_param msr_param;
>>  	cpumask_var_t cpu_mask;
>> @@ -791,8 +791,8 @@ static int reset_all_cbms(struct rdt_resource *r)
>>  		return -ENOMEM;
>>
>>  	msr_param.res = r;
>> -	msr_param.low = 0;
>> -	msr_param.high = r->num_closid;
>> +	msr_param.low = sclosid;
>> +	msr_param.high = eclosid;
>>
>>  	/*
>>  	 * Disable resource control for this resource by setting all
>> @@ -802,7 +802,7 @@ static int reset_all_cbms(struct rdt_resource *r)
>>  	list_for_each_entry(d, &r->domains, list) {
>>  		cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
>>
>> -		for (i = 0; i < r->num_closid; i++)
>> +		for (i = sclosid; i < eclosid; i++)
>
> 'eclosid' or even when named 'end' is an outright bogus argument to this
> function. What you really want is:
>
> static int reset_all_ctrls(struct rdt_resource *r, u32 closid, u32 count)
>
> which works here:
>
>>  	for_each_enabled_rdt_resource(r)
>> -		reset_all_cbms(r);
>> +		reset_all_ctrls(r, 0, r->num_closid);
>
> and makes this part understandable:
>
>> +	/*
>> +	 * Put domain control values back to default for the
>> +	 * rdtgrp thats being removed.
>> +	 */
>> +	for_each_enabled_rdt_resource(r)
>> +		reset_all_ctrls(r, rdtgrp->closid, rdtgrp->closid + 1);
>
> 		reset_all_ctrls(r, rdtgrp->closid, 1);

Will fix the parameters to start and count..

>
> What you have done:
>
>> +		reset_all_ctrls(r, rdtgrp->closid, rdtgrp->closid + 1);
>
> made me really look twice to figure out what the heck this is about.
>
> Thanks,
>
> 	tglx
>