linux-kernel - Re: [Patch v8 06/12] perf/x86/intel/ds: Factor out PEBS record processing code to functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <da62c4ed-ce15-45cc-94f6-3689b8f46d14@linux.intel.com>
Date: Wed, 22 Oct 2025 13:32:38 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo
 <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Dapeng Mi <dapeng1.mi@...el.com>, Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [Patch v8 06/12] perf/x86/intel/ds: Factor out PEBS record
 processing code to functions


On 10/21/2025 11:49 PM, Peter Zijlstra wrote:
> On Wed, Oct 15, 2025 at 02:44:16PM +0800, Dapeng Mi wrote:
>
>> +static inline void __intel_pmu_handle_pebs_record(struct pt_regs *iregs,
>> +						  struct pt_regs *regs,
>> +						  struct perf_sample_data *data,
>> +						  void *at, u64 pebs_status,
>> +						  struct perf_event *events[],
>> +						  short *counts, void **last,
>> +						  setup_fn setup_sample)
>> +{
>> +	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
>> +	struct perf_event *event;
>> +	int bit;
>> +
>> +	for_each_set_bit(bit, (unsigned long *)&pebs_status, X86_PMC_IDX_MAX) {
>> +		event = cpuc->events[bit];
>> +
>> +		if (WARN_ON_ONCE(!event) ||
>> +		    WARN_ON_ONCE(!event->attr.precise_ip))
>> +			continue;
>> +
>> +		if (counts[bit]++)
>> +			__intel_pmu_pebs_event(event, iregs, regs, data,
>> +					       last[bit], setup_sample);
> No brackets, while coding style requires.

Sure. Not sure why checkpatch.pl doesn't found it. Thanks.


>
>> +
>> +		last[bit] = at;
>> +		/*
>> +		 * perf_event_overflow() called by below __intel_pmu_pebs_last_event()
>> +		 * could trigger interrupt throttle and clear all event pointers of
>> +		 * the group in cpuc->events[] to NULL. So snapshot the event[] before
>> +		 * it could be cleared. This avoids the possible NULL event pointer
>> +		 * access and PEBS record loss.
>> +		 */
>> +		if (counts[bit] && !events[bit])
>> +			events[bit] = cpuc->events[bit];
>> +	}
>> +}
>
>> @@ -2671,41 +2728,15 @@ static void intel_pmu_drain_pebs_icl(struct pt_regs *iregs, struct perf_sample_d
>>  		if (basic->format_size != cpuc->pebs_record_size)
>>  			continue;
>>  
>> -		pebs_status = basic->applicable_counters & cpuc->pebs_enabled & mask;
>> -		for_each_set_bit(bit, (unsigned long *)&pebs_status, X86_PMC_IDX_MAX) {
>> -			event = cpuc->events[bit];
>> -
>> -			if (WARN_ON_ONCE(!event) ||
>> -			    WARN_ON_ONCE(!event->attr.precise_ip))
>> -				continue;
>> -
>> -			if (counts[bit]++) {
>> -				__intel_pmu_pebs_event(event, iregs, regs, data, last[bit],
>> -						       setup_pebs_adaptive_sample_data);
>> -			}
> Brackets. Which suggests you took effort to remove them, since cut-paste
> code movement would've preserved them.
>
> I've re-instated them.
>
>> -			last[bit] = at;
>> -
>> -			/*
>> -			 * perf_event_overflow() called by below __intel_pmu_pebs_last_event()
>> -			 * could trigger interrupt throttle and clear all event pointers of
>> -			 * the group in cpuc->events[] to NULL. So snapshot the event[] before
>> -			 * it could be cleared. This avoids the possible NULL event pointer
>> -			 * access and PEBS record loss.
>> -			 */
>> -			if (counts[bit] && !events[bit])
>> -				events[bit] = cpuc->events[bit];
>> -		}
>> +		pebs_status = mask & basic->applicable_counters;
>> +		__intel_pmu_handle_pebs_record(iregs, regs, data, at,
>> +					       pebs_status, events, counts, last,
>> +					       setup_pebs_adaptive_sample_data);