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

From: Ingo Molnar
Date: Wed Aug 26 2009 - 05:17:12 EST

* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:

> On Fri, Aug 21, 2009 at 04:28:11PM +0200, Ingo Molnar wrote:
> >
> > * K.Prasad <prasad@xxxxxxxxxxxxxxxxxx> 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?
> No, we don't need to build an arch level pmu since the BP api
> already handles the arch abstraction (or well, it is planned to).
> Instead, what we need is a core pmu that relies on the BP api.
> Such pmu will be allocated dynamically while creating a hardware
> breakpoint counter.

i'm not convinced at all we need all that layering of
perfcounters->pmu->BP. Why not add BP support to the PMU abstraction
and be done with it?

That way we get hardware breakpoints via 'pinned, exclusive, per cpu
hw-breakpoint counters' for example and kernel/hw-breakpoint.c can
go away altogether.

kernel/perf_counter.c already handles scheduling, conflict
resolution, enumeration, syscall exposure and more.


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