linux-kernel - Re: [Patch 0/1] HW-BKPT: Allow per-cpu kernel-space Hardware Breakpoint requests

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Date:	Fri, 21 Aug 2009 16:28:11 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [Patch 0/1] HW-BKPT: Allow per-cpu kernel-space Hardware
	Breakpoint requests


* K.Prasad <prasad@...ux.vnet.ibm.com> wrote:

> > Providing those would let us build a pmu struct on top of this 
> > high level API, hopefully.

Note that there's a PMU struct already in 
arch/x86/kernel/cpu/perf_counter.c. Could debug-register ops be 
tacked on to it?

> > All that would be a benefit in both sides. It avoids us building 
> > a low level PMU that reinvent the wheel, ie: the hardware 
> > breakpoints API handles a lot of things both in arch and core 
> > sides (debug register setting tricks with dr7 and co, cpu 
> > hotplug, kexec, etc...). In the bp API it brings more power 
> > (register switching only if needed, per cpu support, clone 
> > inheritance support, etc...)
> > 
> > And in the end we have a pmu (which unifies the control of this 
> > profiling unit through a well established and known object for 
> > perfcounter) controlled by a high level API that could also 
> > benefit to other debugging subsystems.
> > 
> > What do you think? It would be also nice to have Peter's and 
> > Ingo opinion about it, to be sure we are not going in the wrong 
> > direction.
> 
> Indeed, it will be nice to know from Ingo and Peter that we are 
> heading right.

If you do this proper perfcounters integration then i'm certainly 
happy.

	Ingo
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