Re: [RFC PATCH 0/3]perf/core: extend perf_reg and perf_sample_regs_intr

On Friday 06 November 2015 08:28 AM, Sukadev Bhattiprolu wrote:

Peter Zijlstra [peterz@infradead.org] wrote:
| On Thu, Nov 05, 2015 at 02:16:15AM +0530, Madhavan Srinivasan wrote:
| > Second patch updates struct arch_misc_reg for arch/powerpc with pmu registers
| > and adds offsetof macro for the same. It extends perf_reg_value()
| > to use reg idx to decide on struct to return value from.
| 
| Why; what's in those regs?

Those are PMU control registers/counters (in Patch 2) that are of
interest only in the context of a PMU interrupt and not relevant
to ptrace itself.

Yes. Thats right.

Could we add those registers to 'struct pt_regs' anyway?

I would prefer not to. Since as you mentioned, these are
not relevant to ptrace. Currently patch 2, adds only few
pmu registers, but would like to include more.
 

We do have 'struct perf_regs' but that seems to be arch nuetral.
If architectures could override that, maybe we could add these
new registers there without touching 'struct pt_regs'.

Exactly, idea here is to capture more data using perf_sample_reg_intr
without extending pt_regs structure.

Maddy

Even so, lot of perf code depends on 'struct pt_regs'.

Sukadev