linux-kernel - Re: [PATCH 09/14] perf, x86: use LBR for PEBS IP+1 fixup

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Date:	Thu, 04 Mar 2010 18:54:22 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org, paulus@...ba.org,
	eranian@...gle.com, robert.richter@....com, fweisbec@...il.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH 09/14] perf, x86: use LBR for PEBS IP+1 fixup

On Thu, 2010-03-04 at 11:21 -0500, Masami Hiramatsu wrote:
> Peter Zijlstra wrote:

> > +#define perf_misc_flags(regs)				\
> > +({	int misc = 0;					\
> > +	if (user_mode(regs))				\
> > +		misc |= PERF_RECORD_MISC_USER;		\
> > +	else						\
> > +		misc |= PERF_RECORD_MISC_KERNEL;	\
> > +	if (regs->flags & PERF_EFLAGS_EXACT)		\
> > +		misc |= PERF_RECORD_MISC_EXACT;		\
> > +	misc; })
> > +
> > +#define perf_instruction_pointer(regs)	((regs)->ip)
> 
> Hmm, why don't you use instruction_pointer() defined in asm/ptrace.h?
> And I couldn't find any user of this macro in this patch...

perf_instruction_pointer() is used in kernel/perf_event.c, and yeah I
could have used instruction_pointer() but that's yet another wrapper.

Anyway, Yanmin is poking at doing kvm-guest profiling and will likely
rewrite all of the perf_misc() and perf_instruction_pointer() stuff
soon.

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