Re: [PATCH 2/9] perf thread-stack: Report branch stack hw_idx as not available
Adrian Hunter <[email protected]>
| Newsgroups | org.kernel.vger.linux-doc,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-perf-users |
|---|---|
| Organization | Intel Finland Oy, Registered Address: c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo, Business Identity Code: 0357606 - 4, Domiciled in Helsinki |
| Message-ID | <[email protected]> |
On 03/08/2026 12:06, Amir Ayupov wrote: > thread_stack__br_sample() and thread_stack__br_sample_late() fill a > caller-supplied branch_stack that is typically allocated with zalloc(), > leaving hw_idx as 0. Zero is a valid hardware index, so consumers that > honour PERF_SAMPLE_BRANCH_HW_INDEX see a reconstructed branch stack > claiming to start at LBR TOS entry 0. > > These branch stacks are reconstructed from instruction trace and have no > hardware index at all. Set hw_idx to -1ULL, which is the established way > to say "not available" and matches what intel-pt and cs-etm already put > in the branch stacks they synthesise directly. > > Signed-off-by: Amir Ayupov <[email protected]> Fixes tag? Otherwise: Reviewed-by: Adrian Hunter <[email protected]> > --- > tools/perf/util/thread-stack.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c > index c5ce741b07446..1a3dffa83bde2 100644 > --- a/tools/perf/util/thread-stack.c > +++ b/tools/perf/util/thread-stack.c > @@ -624,6 +624,7 @@ void thread_stack__br_sample(struct thread *thread, int cpu, > unsigned int nr; > > dst->nr = 0; > + dst->hw_idx = -1ULL; > > if (!ts) > return; > @@ -686,6 +687,7 @@ void thread_stack__br_sample_late(struct thread *thread, int cpu, > bool start = false; > > dst->nr = 0; > + dst->hw_idx = -1ULL; > > if (!ts) > return;