From: "Liang, Kan" <kan.liang@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>, LKML <linux-kernel@vger.kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>, "x86@kernel.org" <x86@kernel.org>,
        Stephane Eranian <eranian@google.com>, Borislav Petkov <bp@suse.de>,
        "Andi Kleen (ak@linux.intel.com)" <ak@linux.intel.com>
Subject: RE: [patch 2/4] x86/perf/intel/cstate: Sanitize probing
Thread-Topic: [patch 2/4] x86/perf/intel/cstate: Sanitize probing
Thread-Index: AQHRgtrSKWxUAB1xQkadBOnglt+kv59j7zaw
Date: Mon, 21 Mar 2016 14:19:27 +0000
Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077058A7665@SHSMSX103.ccr.corp.intel.com>
References: <20160320185527.763205536@linutronix.de>
 <20160320185623.500381872@linutronix.de>
In-Reply-To: <20160320185623.500381872@linutronix.de>
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>  /*
>   * 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;
>  }
>