linux-kernel - Re: perf_fuzzer compiled for x32 causes reboot

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Message-ID: <20140301091650.GD5885@gmail.com>
Date:	Sat, 1 Mar 2014 10:16:50 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: perf_fuzzer compiled for x32 causes reboot


* Steven Rostedt <rostedt@...dmis.org> wrote:

> > Also, this function is called a _LOT_ under certain workloads, I 
> > don't know how cheap a CR2 read is, but it had better be really 
> > cheap.
> 
> That's a HPA question.

We read CR2 in the page fault hot path, so it's on the top of CPU 
architects' minds and it's reasonably optimized. A couple of cycles 
IIRC, but would be nice to hear actual numbers.

Thanks,

	Ingo
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