Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Vince Weaver <vincent.weaver@maine.edu>
Date:   Thu, 11 Feb 2021 17:14:50 -0500 (EST)
To:     "Liang, Kan" <kan.liang@linux.intel.com>
cc:     Peter Zijlstra <peterz@infradead.org>,
        Vince Weaver <vincent.weaver@maine.edu>,
        linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [perf] perf_fuzzer causes crash in intel_pmu_drain_pebs_nhm()
In-Reply-To: <d2005608-4214-ec01-d6b1-a7d19fab7bf9@linux.intel.com>
Message-ID: <2a655469-de9d-c80-dd7f-26436d6f03a@maine.edu>
References: <61a56699-aab4-ef6-ed8d-a22b6bf532d@maine.edu> <7170d3b-c17f-1ded-52aa-cc6d9ae999f4@maine.edu> <YCVE8q4MlbcU4fnV@hirez.programming.kicks-ass.net> <d2005608-4214-ec01-d6b1-a7d19fab7bf9@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Thu, 11 Feb 2021, Liang, Kan wrote:

> > On Thu, Jan 28, 2021 at 02:49:47PM -0500, Vince Weaver wrote:
> I'd like to reproduce it on my machine.
> Is this issue only found in a Haswell client machine?
> 
> To reproduce the issue, can I use ./perf_fuzzer under perf_event_tests/fuzzer?
> Do I need to apply any parameters with ./perf_fuzzer?
> 
> Usually how long does it take to reproduce the issue?

On my machine if I run the commands
		echo 1 > /proc/sys/kernel/nmi_watchdog
                echo 0 > /proc/sys/kernel/perf_event_paranoid
                echo 1000 > /proc/sys/kernel/perf_event_max_sample_rate
                ./perf_fuzzer -s 30000 -r 1611784483

it is repeatable within a minute, but because of the nature of the fuzzer 
it probably won't work for you because the random events will diverge 
based on the different configs of the system.

I can try to generate a simple reproducer, I've just been extremely busy 
here at work and haven't had the chance.

If you want to try to reproduce it the hard way, run the
	./fast_repro99.sh
script in the perf_fuzzer directory.  It will start fuzzing.  My machine 
turned up the issue within a day or so.

Vince