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: <20251021154930.GS3245006@noisy.programming.kicks-ass.net>
Date: Tue, 21 Oct 2025 17:49:30 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Dapeng Mi <dapeng1.mi@...ux.intel.com>
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 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.

> +
> +		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);