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Fri, 6 Nov 2026 15:31:40 +0000 (GMT) Received: from li-fbf77acc-29ba-11b2-a85c-e8e934f50a46.ibmuc.com (unknown [9.39.29.160]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 6 Nov 2026 15:31:39 +0000 (GMT) From: Gautam Menghani To: maddy@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au, chleroy@kernel.org, ritesh.list@gmail.com, sshegde@linux.ibm.com, atrajeev@linux.ibm.com, tshah@linux.ibm.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 0/3] powerpc/perf: Fix vpa-pmu driver to report correct numbers Date: Fri, 6 Nov 2026 21:01:31 +0530 Message-ID: <20261106153136.330165-1-gautam@linux.ibm.com> X-Mailer: git-send-email 2.56.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYxMTA2MDA2MCBTYWx0ZWRfX6ZVdLCTgEOnB 7a2ZhXbxKLpCkVdy/WIGqsneso5V6xU0tYeUVKbVCzS0/eSMtxqe9WOc58GpTntZ7mwkO3S6rlE cYE4WG3aNsI+WrmUpAbft7Sx84ITejI= X-Proofpoint-GUID: ZXkr24dVxlue3lFuDPzDe9GJ_698cUWx X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTA2MDA2MCBTYWx0ZWRfX9Sfk1KWupinf g2dpgDk76q20uQKIL9un4fjYguFvdZcCk9aPDqE3fo0ZHpXUeEeoD47i9y18So8Z08kYYU7yhOU 689hiwJft57CsGOKJbkZ54UHAWuHL1jHZ5ahYcrapA2NdYzgmROMdq4F13ZQ+iKP6Szhe8eAWiQ FMiJHFP75LNuQTfbzxT9tiHNTq5B+YGywMRGXnggPzjl8vme/KSN1nkHI1ljTjqcEmttHxpf8nr x25NiU6d2jhbo680b85YGeMx4nL+WmJoWvpRbswdS3WME8Nk1l9K5T2qAokk8R3n02eNB73db9Y WOayU4O3rQuz84DdvPUkF2cYdbF16GJEiNSc1sCNWfVL2W32EXaX89xXwt/yBmIkuRcqKru6kPL SdMtG0aOpUIgNBKEiWav/86Dzo1SaNS2pPfyKzX3rOMLHW/y3WdJZ0R+ZQ8A/yVVes1WbYTkyhL R7HAEkWlpHRGLpdyhag== X-Proofpoint-ORIG-GUID: TYM7-z7ONl445plmQtla8OWbCb5rRkUg X-Authority-Analysis: v=2.4 cv=CY+dd7rl c=1 sm=1 tr=0 ts=6aedf2e3 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=aSoOVV5oyB5p4QsdXGgA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-06_05,2026-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 bulkscore=0 phishscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611060060 The vpa-pmu driver can sometimes report incorrect context switch latency numbers: $ perf stat -e vpa_pmu/l1_to_l2_lat/ --tid=2061 -I 1000 time counts unit events 1.001022517 18,446,744,073,708,177,408 vpa_pmu/l1_to_l2_lat/ 2.002120674 345,092 vpa_pmu/l1_to_l2_lat/ 3.003171582 406,342 vpa_pmu/l1_to_l2_lat/ 4.004234838 340,836 vpa_pmu/l1_to_l2_lat/ These invalid numbers are observed because of 2 issues: 1. The PACA never points to the correct vCPU running on a host vCPU when vpa_pmu_add() is called. 2. When get_counter_data() reads the PACA counter values, it does not update the event->hw.prev_count. Changes in V3: 1. Drop the usage of the PACA's vCPU pointer. 2. Introduce a new patch to fix an issue seen when a tracepoint and vpa-pmu driver concurrently enable/disable access to latency counters in VPA. Gautam Menghani (3): Revert "powerpc/perf: Add per-task/process monitoring to vpa_pmu driver" powerpc/perf: Update prev_count of event to get accurate values KVM: PPC: Book3s HV: Ensure reliable usage of latency counters arch/powerpc/include/asm/kvm_book3s_64.h | 3 -- arch/powerpc/kvm/book3s_hv.c | 54 +++--------------------- arch/powerpc/perf/vpa-pmu.c | 16 ++----- 3 files changed, 11 insertions(+), 62 deletions(-) -- 2.56.0