linux-kernel - Re: [PATCH] perf: Fix interpretation of branch records

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Message-ID: <Y4pFE1bNObTTLL2+@kernel.org>
Date:   Fri, 2 Dec 2022 15:33:55 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, sandipan.das@....com,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH] perf: Fix interpretation of branch records

Em Thu, Dec 01, 2022 at 09:46:53AM +0530, Anshuman Khandual escreveu:
> 
> 
> On 11/30/22 22:21, James Clark wrote:
> > Commit 93315e46b000 ("perf/core: Add speculation info to branch
> > entries") added a new field in between type and new_type. Perf has
> > its own copy of this struct so update it to match the kernel side.
> > 
> > This doesn't currently cause any issues because new_type is only used
> > by the Arm BRBE driver which isn't merged yet.
> > 
> > Fixes: 93315e46b000 ("perf/core: Add speculation info to branch entries")
> > Signed-off-by: James Clark <james.clark@....com>
> 
> Again, problem from having the same structure in two different places

Indeed, this was my first reaction, how about backward compatibility, is
this really an ABI?

- Arnaldo
 
> Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
 
> > ---
> >  tools/perf/util/branch.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/branch.h b/tools/perf/util/branch.h
> > index d6017c9b1872..3ed792db1125 100644
> > --- a/tools/perf/util/branch.h
> > +++ b/tools/perf/util/branch.h
> > @@ -22,9 +22,10 @@ struct branch_flags {
> >  			u64 abort:1;
> >  			u64 cycles:16;
> >  			u64 type:4;
> > +			u64 spec:2;
> >  			u64 new_type:4;
> >  			u64 priv:3;
> > -			u64 reserved:33;
> > +			u64 reserved:31;
> >  		};
> >  	};
> >  };

-- 

- Arnaldo