linux-kernel - Re: [PATCH] x86: Rename copy_from_user_nmi() to copy_from_user

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Message-ID: <20140228211730.GG14089@laptop.programming.kicks-ass.net>
Date:	Fri, 28 Feb 2014 22:17:30 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	"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: [PATCH] x86: Rename copy_from_user_nmi() to
 copy_from_user_trace()

On Fri, Feb 28, 2014 at 04:01:39PM -0500, Steven Rostedt wrote:
> OK, I'll go with that. So instead of an _nmi() which it has nothing to
> do with NMIs, 

Well, how is 'safe to use from NMI' nothing to do with NMIs?

> how about making it like spin_lock_irq() and a more
> descriptive name about what it does?
> 
>  copy_from_user_savecr2()

So how expensive are these CR2 reads? Because if they're more expensive
than one or two cycles (normal instructions) I'd really rather not put
them in there.

I seem to have missed what was wrong with Jiri's patch. Are we worried
about the function trace events?

So IF we're going to push them into this side of things; I'd really
rather see the CR2 foo in perf_callchain_user() and make
arch_perf_out_copy_user() a real function which includes the CR2 goo
too.
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