linux-kernel - Re: [PATCH v1 00/11] perf script: Refactor branch flags for Arm SPE

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Message-ID: <20250214113249.GA6174@e132581.arm.com>
Date: Fri, 14 Feb 2025 11:32:49 +0000
From: Leo Yan <leo.yan@....com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Ian Rogers <irogers@...gle.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
	James Clark <james.clark@...aro.org>,
	Mike Leach <mike.leach@...aro.org>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Graham Woodward <graham.woodward@....com>
Subject: Re: [PATCH v1 00/11] perf script: Refactor branch flags for Arm SPE

Hi Ian, Namhyung,

On Wed, Feb 12, 2025 at 09:29:28PM -0800, Namhyung Kim wrote:

[...]

> > > > Built and tested (on x86). A little strange patch 5 adds a new bit not
> > > > at the end, but "Sample parsing" test wasn't broken so looks like it
> > > > is good. I was surprised the use of value in the union:
> > > > ```
> > > > struct branch_flags {
> > > > union {
> > > > u64 value;
> > > > struct {
> > > > u64 mispred:1;
> > > > u64 predicted:1;
> > > > ...
> > > > ```
> > > > didn't get broken. Perhaps there's an opportunity for additional tests.
> 
> Probably because it just checks the value as a whole u64, not each
> bitfield.  But it seems to test if the value of the input sample data
> and synthesized-and-parsed output sample data is same.  So it may not be
> important what value it has.
> 
> Anyway it'd be nice if any ARM folks can review this series.

After discussed with James, I concluded that it has risk to break
other arches (e.g., x86 LBR).  So I have sent out patch set v2 [1]
to keep the existed bitfield layout in patch 05, and added Ian's
review tags.

I expect James will give a review the new series.

Thanks,
Leo

[1] https://lore.kernel.org/linux-perf-users/20250214111936.15168-1-leo.yan@arm.com/T/#t