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

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Date:   Thu, 1 Dec 2022 14:32:14 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, acme@...nel.org,
        Anshuman.Khandual@....com
Cc:     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

On 11/30/2022 10:21 PM, 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")

Technically, in the kernel sources, commit 93315e46b000 ("perf/core: Add
speculation info to branch entries") landed before commit b190bc4ac9e6
("perf: Extend branch type classification").

So I think the Fixes tag should instead have commit 0ddea8e2a0c2
("perf branch: Extend branch type classification") which added the
UAPI changes to the perf tool headers.

Aside from that, the patch looks good to me.

> Signed-off-by: James Clark <james.clark@....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;
>  		};
>  	};
>  };