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Mon, 03 Aug 2026 02:06:43 -0700 (PDT) Received: from localhost (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c08b:78::2ac9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.2.2562.45; Mon, 3 Aug 2026 09:06:42 +0000 From: Amir Ayupov To: , , , Suzuki K Poulose , James Clark , Leo Yan , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , John Garry , Will Deacon CC: , Mike Leach , Jonathan Corbet , Shuah Khan , Swapnil Sapkal Subject: [PATCH 2/9] perf thread-stack: Report branch stack hw_idx as not available Date: Mon, 3 Aug 2026 02:06:33 -0700 Message-ID: <20260803090640.2412336-2-aaupov@fb.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260803090640.2412336-1-aaupov@fb.com> References: <20260803090640.2412336-1-aaupov@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [2620:10d:c085:208::f] X-Proofpoint-ORIG-GUID: pvrznZBnpB91_2NTEiNB_sZCTbJZ0Ta0 X-Proofpoint-Spam-Info: AW1haW4tMjYwODAzMDA4MSBTYWx0ZWRfXzV2QmRQ0/eSt 6AQVobwJUgaY2hfKbvuBVDtNXVQKGQvgvYmSGcCgmqWo//nVJXy7KnJ9811c8nsvz+GgeiOKvlI 5dcK9xDSpgEqxcL0kSeOiXoVFRbBJOs= X-Proofpoint-GUID: pvrznZBnpB91_2NTEiNB_sZCTbJZ0Ta0 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODAzMDA4MSBTYWx0ZWRfX306oAGCw+eZQ PoccYJzHNQqelf5HYONXdUjJ7cLcjM8DcVp4I8FuziGoTCUXRG/wj+xy95DBqhvcI0kqo0KntVo 7hg1xQCoouWmg69gCtZY4+LUUHeszpAMVSbesrkOeVzeAszj4pJwtUbLgGHENyKBLkI35JqMPJK B0ce3WFrTKZW3HMbMEqy+axdk1aR3RWLh3tmpOXrs8q9mMYzfU7IdrYnH8iEFyrm3Yf5qREW97C /HzNFx9SfYBa/81jg9apntldSsfTL1YmkkB8AlO+u7li0GF4yLYe6C6Ciz+VXuCFilksBv8URm9 AXpR9ketFfk2mVCLSqhYS24u9uncP3+GiiyYIOFBPmjAEbMdCqKOZKC/ZwZXZG4atb3wyv29VWB p9pef/tCJV74M//hbnXzOfHitYtts0BCMQ9PQCQhW/OlfWmpLoQaWjiy4A2ekYm0QidfhzQsfXH 2TRrce7Jo8PPs58Y4AA== X-Authority-Analysis: v=2.4 cv=auGCzyZV c=1 sm=1 tr=0 ts=6a705a23 cx=c_pps a=CB4LiSf2rd0gKozIdrpkBw==:117 a=CB4LiSf2rd0gKozIdrpkBw==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=7x6HtfJdh03M6CCDgxCd:22 a=03ozwUkBphtHgyqjj1sw:22 a=FOH2dFAWAAAA:8 a=tFPw7G4F2t7FTvsiR7UA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-02_06,2026-07-30_01,2025-10-01_01 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260803_020659_699857_CA35B11D X-CRM114-Status: GOOD ( 13.01 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 --- 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; -- 2.52.0