linux-kernel - RE: [patch 2/4] x86/perf/intel/cstate: Sanitize probing

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Date:	Mon, 21 Mar 2016 14:19:27 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	"x86@...nel.org" <x86@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Borislav Petkov <bp@...e.de>,
	"Andi Kleen (ak@...ux.intel.com)" <ak@...ux.intel.com>
Subject: RE: [patch 2/4] x86/perf/intel/cstate: Sanitize probing



>  /*
>   * Probe the cstate events and insert the available one into sysfs attrs
> - * Return false if there is no available events.
> + * Return false if there are no available events.
>   */
> -static bool cstate_probe_msr(struct perf_cstate_msr *msr,
> -			     struct attribute	**events_attrs,
> -			     int max_event_nr)
> +static bool __init cstate_probe_msr(const unsigned long evmsk,
> +				    struct perf_cstate_msr *msr,
> +				    struct attribute **attrs)
>  {
> -	int i, j = 0;
> +	bool found = false;
> +	unsigned int bit;
>  	u64 val;
> 
> -	/* Probe the cstate events. */
> -	for (i = 0; i < max_event_nr; i++) {
> -		if (!msr[i].test(i) || rdmsrl_safe(msr[i].msr, &val))
> -			msr[i].attr = NULL;
> -	}

I think we need to update msr[i].attr as well.
Because in cstate_pmu_event_init we still need it to do check.

Thanks,
Kan
> -
> -	/* List remaining events in the sysfs attrs. */
> -	for (i = 0; i < max_event_nr; i++) {
> -		if (msr[i].attr)
> -			events_attrs[j++] = &msr[i].attr->attr.attr;
> +	for_each_set_bit(bit, &evmsk, sizeof(evmsk) * BITS_PER_BYTE) {
> +		/* Verify whether the MSR is accessible */
> +		if (!rdmsrl_safe(msr[bit].msr, &val)) {
> +			*attrs++ = &msr[bit].attr->attr.attr;
> +			found = true;
> +		}
>  	}
> -	events_attrs[j] = NULL;
> -
> -	return (j > 0) ? true : false;
> +	*attrs = NULL;
> +	return found;
>  }
>