linux-kernel - Re: perf: rdpmc bug when viewing all procs on remote cpu

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Message-ID: <alpine.DEB.2.21.1901101246340.3358@macbook-air>
Date:   Thu, 10 Jan 2019 12:50:53 -0500 (EST)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: perf: rdpmc bug when viewing all procs on remote cpu

On Thu, 10 Jan 2019, Vince Weaver wrote:

> However if you create an all-process attached to CPU event:
> 	perf_event_open(attr, -1, X, -1, 0);
> the mmap event index is set as if this were a valid event and so the rdpmc
> succeeds even though it shouldn't (we're trying to read an event value
> on a remote cpu with a local rdpmc).

For a test case, try the
	tests/rdpmc/rdpmc_attach_other_cpu
test found in my perf_event_tests suite
	git clone https://github.com/deater/perf_event_tests

I can trigger it with current git on an intel machine, but not on an AMD 
machine.  Possibly because it is defaulting to one of the fixed counter 
slots?

Vince