linux-kernel - Re: [Patch v3 3/7] perf/x86: Check if cpuc->events[*] pointer exists before accessing it

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] [day] [month] [year] [list]

Message-ID: <aKZ7omM0-3i72hfr@tassilo>
Date: Wed, 20 Aug 2025 18:51:30 -0700
From: Andi Kleen <ak@...ux.intel.com>
To: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>, 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>,
	Kan Liang <kan.liang@...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>,
	kernel test robot <oliver.sang@...el.com>
Subject: Re: [Patch v3 3/7] perf/x86: Check if cpuc->events[*] pointer exists
 before accessing it

On Wed, Aug 20, 2025 at 01:54:17PM +0800, Mi, Dapeng wrote:
> 
> On 8/20/2025 1:44 PM, Andi Kleen wrote:
> >> Andi, I didn't fully get the exact meaning about the "log" here. When
> >> throttle is triggered, perf_event_throttle() has already called
> >> perf_log_throttle() to log the throttle event although only for the group
> >> leader. Is it enough?
> > Throttle normally doesn't involve data loss, just less samples. But this
> > is data loss, so it's an overflow.
> 
> IIUC, there should be no data loss, the unprocessed PEBS records of these
> throttled events would be still processed eventually by calling
> intel_pmu_drain_pebs_buffer() when stopping the event.

Makes sense. Thanks,
-Andi