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Sun, 2 Mar 2025 22:03:36 GMT Received: from pps.reinject (localhost [127.0.0.1]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 453rp803fm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 02 Mar 2025 22:03:36 +0000 Received: from phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 522M3Qoj040088; Sun, 2 Mar 2025 22:03:35 GMT Received: from localhost.localdomain (ca-dev80.us.oracle.com [10.211.9.80]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTP id 453rp80353-11; Sun, 02 Mar 2025 22:03:35 +0000 From: Dongli Zhang To: qemu-devel@nongnu.org, kvm@vger.kernel.org Cc: pbonzini@redhat.com, zhao1.liu@intel.com, mtosatti@redhat.com, sandipan.das@amd.com, babu.moger@amd.com, likexu@tencent.com, like.xu.linux@gmail.com, zhenyuw@linux.intel.com, groug@kaod.org, khorenko@virtuozzo.com, alexander.ivanov@virtuozzo.com, den@virtuozzo.com, davydov-max@yandex-team.ru, xiaoyao.li@intel.com, dapeng1.mi@linux.intel.com, joe.jin@oracle.com Subject: [PATCH v2 10/10] target/i386/kvm: don't stop Intel PMU counters Date: Sun, 2 Mar 2025 14:00:18 -0800 Message-ID: <20250302220112.17653-11-dongli.zhang@oracle.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250302220112.17653-1-dongli.zhang@oracle.com> References: <20250302220112.17653-1-dongli.zhang@oracle.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-03-02_06,2025-02-28_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 suspectscore=0 phishscore=0 adultscore=0 mlxlogscore=999 malwarescore=0 spamscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2502100000 definitions=main-2503020180 X-Proofpoint-ORIG-GUID: fcG2tYD14NBusWqgi361T_u3mqxCmJm5 X-Proofpoint-GUID: fcG2tYD14NBusWqgi361T_u3mqxCmJm5 The kvm_put_msrs() sets the MSRs using KVM_SET_MSRS. The x86 KVM processes these MSRs one by one in a loop, only saving the config and triggering the KVM_REQ_PMU request. This approach does not immediately stop the event before updating PMC. In additional, PMU MSRs are set only at levels >= KVM_PUT_RESET_STATE, excluding runtime. Therefore, updating these MSRs without stopping events should be acceptable. Finally, KVM creates kernel perf events with host mode excluded (exclude_host = 1). While the events remain active, they don't increment the counter during QEMU vCPU userspace mode. No Fixed tag is going to be added for the commit 0d89436786b0 ("kvm: migrate vPMU state"), because this isn't a bugfix. Signed-off-by: Dongli Zhang --- target/i386/kvm/kvm.c | 9 --------- 1 file changed, 9 deletions(-) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index c5911baef0..4902694129 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -4160,13 +4160,6 @@ static int kvm_put_msrs(X86CPU *cpu, int level) } if (IS_INTEL_CPU(env) && has_pmu_version > 0) { - if (has_pmu_version > 1) { - /* Stop the counter. */ - kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, 0); - kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_CTRL, 0); - } - - /* Set the counter values. */ for (i = 0; i < num_pmu_fixed_counters; i++) { kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR0 + i, env->msr_fixed_counters[i]); @@ -4182,8 +4175,6 @@ static int kvm_put_msrs(X86CPU *cpu, int level) env->msr_global_status); kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_OVF_CTRL, env->msr_global_ovf_ctrl); - - /* Now start the PMU. */ kvm_msr_entry_add(cpu, MSR_CORE_PERF_FIXED_CTR_CTRL, env->msr_fixed_ctr_ctrl); kvm_msr_entry_add(cpu, MSR_CORE_PERF_GLOBAL_CTRL,