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Tue, 11 Aug 2026 14:03:20 +0000 (GMT) Received: from localhost.localdomain (unknown [9.124.219.6]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 11 Aug 2026 14:03:19 +0000 (GMT) From: Gautam Menghani To: maddy@linux.ibm.com, atrajeev@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au, chleroy@kernel.org Cc: Gautam Menghani , linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/3] powerpc/perf: Fix vpa-pmu driver to report correct Date: Tue, 11 Aug 2026 19:33:06 +0530 Message-ID: <20260811140313.15397-1-gautam@linux.ibm.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=RsP16imK c=1 sm=1 tr=0 ts=6a7b2baf cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=2wL9yz101uEFEcatHFYA:9 X-Proofpoint-GUID: jE-68-cucBNX4sFAfjca3-3i-bUQtCL0 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODExMDExNyBTYWx0ZWRfX8Sg/UTiNgZBD 9N/Z+dkdACQbqtaiX/fPi6U8umhmZovD6FrcWTQifKPgx9N5vpvoY25jyc2Zp1AdeVcpEJBcQPT l+KyREaJFa+xRUqaLqONiQqOsORops7wfTmYmCdGj7pRulLPviXf/8WIX1V1JD+gLoHu9/ZpqyV fsILfDdHjlWB1VAOjOvBwkXuGTGWnWrROJp9tfwSMAtSacMQmD2LwOVuKVEl1bfnEIxAWUtFKC3 xNMvRap4CsYQczFWt6+pW4n1eEkbCoEumsKuSHyXkCi4pleJaLEGiOdeTOvW2nBmfyZSIuU12Q1 JupLgnwiabC/q9Nnp92FfctCeOxyKgfKlGewSXaHlQVOVEoelqrDg+0ISsxEQK1EHja/x9FDcr+ olz3YApCbsy3sGMLNvjypW3OXwWMB7080GzToU41GK+kpWUI5pS+ivP2aXKNPdbyV7T7txkewgz EQUCBzSU1Wd2VRCObFg== X-Proofpoint-ORIG-GUID: l_kpnYccm93pd4ZtELwQOdSjR1-qjyP8 X-Proofpoint-Spam-Info: AW1haW4tMjYwODExMDExNyBTYWx0ZWRfX2d0f2FDynAnh HHbK/3C36NflOjEoLDvtJhVQ+YtjIghdF1O7cZ2Rma6CCDFsWNk/BW97MIb+C+Uw3UB0asYEfag sFM3UPi5rsrNugpXJHfYg3hEgNKlq+I= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-11_03,2026-08-10_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 suspectscore=0 clxscore=1015 malwarescore=0 phishscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608110117 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 the vpa-pmu driver does not handle the following scenarios: 1. The vCPU process gets rescheduled to a different host cpu. 2. The vCPU process is not running, and vpa_pmu_read() is called to read counter values. Fix the above cases by maintaining aggregate counter values inside the vcpu->arch struct and using them to report data. Gautam Menghani (3): KVM: PPC: Book3S HV: Maintain aggregate context switch values for vcpus powerpc/perf: Use the aggregate context switch values from vcpu struct powerpc/perf: Update prev_count of event to get accurate values arch/powerpc/include/asm/kvm_book3s_64.h | 6 -- arch/powerpc/kvm/book3s_hv.c | 69 +---------------------- arch/powerpc/perf/vpa-pmu.c | 70 ++++++++++++------------ 3 files changed, 39 insertions(+), 106 deletions(-) -- 2.54.0