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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.googlemail.com with ESMTPSA id 14-20020a17090602ce00b006fe89cafc42sm3049145ejk.172.2022.05.20.05.51.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 May 2022 05:51:07 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <31f3de9a-a752-e322-ebd0-731c42afd47a@redhat.com> Date: Fri, 20 May 2022 14:51:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH RESEND v3 03/11] KVM: x86/pmu: Protect kvm->arch.pmu_event_filter with SRCU Content-Language: en-US To: Like Xu Cc: Sean Christopherson , Jim Mattson , Vitaly Kuznetsov , Wanpeng Li , Joerg Roedel , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20220518132512.37864-1-likexu@tencent.com> <20220518132512.37864-4-likexu@tencent.com> From: Paolo Bonzini In-Reply-To: <20220518132512.37864-4-likexu@tencent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/18/22 15:25, Like Xu wrote: > From: Like Xu > > Similar to "kvm->arch.msr_filter", KVM should guarantee that vCPUs will > see either the previous filter or the new filter when user space calls > KVM_SET_PMU_EVENT_FILTER ioctl with the vCPU running so that guest > pmu events with identical settings in both the old and new filter have > deterministic behavior. > > Fixes: 66bb8a065f5a ("KVM: x86: PMU Event Filter") > Signed-off-by: Like Xu > Reviewed-by: Wanpeng Li Please always include the call trace where SRCU is not taken. The ones I reconstructed always end up at a place inside srcu_read_lock/unlock: reprogram_gp_counter/reprogram_fixed_counter amd_pmu_set_msr kvm_set_msr_common svm_set_msr __kvm_set_msr kvm_set_msr_ignored_check kvm_set_msr_with_filter kvm_emulate_wrmsr** emulator_set_msr_with_filter** kvm_set_msr emulator_set_msr** do_set_msr __msr_io msr_io ioctl(KVM_SET_MSRS)** intel_pmu_set_msr kvm_set_msr_common vmx_set_msr (see svm_set_msr) reprogram_counter global_ctrl_changed intel_pmu_set_msr (see above) kvm_pmu_handle_event vcpu_enter_guest** kvm_pmu_incr_counter kvm_pmu_trigger_event nested_vmx_run** kvm_skip_emulated_instruction** x86_emulate_instruction** reprogram_fixed_counters intel_pmu_set_msr (see above) Paolo > arch/x86/kvm/pmu.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > index f189512207db..24624654e476 100644 > --- a/arch/x86/kvm/pmu.c > +++ b/arch/x86/kvm/pmu.c > @@ -246,8 +246,9 @@ static bool check_pmu_event_filter(struct kvm_pmc *pmc) > struct kvm *kvm = pmc->vcpu->kvm; > bool allow_event = true; > __u64 key; > - int idx; > + int idx, srcu_idx; > > + srcu_idx = srcu_read_lock(&kvm->srcu); > filter = srcu_dereference(kvm->arch.pmu_event_filter, &kvm->srcu); > if (!filter) > goto out; > @@ -270,6 +271,7 @@ static bool check_pmu_event_filter(struct kvm_pmc *pmc) > } > > out: > + srcu_read_unlock(&kvm->srcu, srcu_idx); > return allow_event; > } >