Hi, Sean: I have found that in the latest version of the kernel, some PMU events are being lost. I used bisect and found out the breaking commit [1], which moved the handling of NMI events from `handle_exception_irqoff` to `vmx_vcpu_enter_exit`. If I revert this part as done in this patch, it works correctly. However, I'm not really familiar with KVM, and I'm not sure about the intent behind the original patch [1]. Could you please take a look on this? Thanks a lot. My use case is to sample the IP of guest OS using `perf kvm`: `perf kvm --guest record -a -g -e instructions -F 10000 -- sleep 1` If it works correctly, it will record about 10000 samples (as `-F 10000`) and it will say: `[ perf record: Captured and wrote 0.9 MB perf.data.guest (9729 samples) ]` And if not, it will only record ~100 samples, sometimes no sample at all. If it's useful for your debug, The callchain of `vmx_vcpu_enter_exit` is: vmx_vcpu_enter_exit vmx_vcpu_run kvm_x86_vcpu_run vcpu_enter_guest While the callchain of `handle_exception_irqoff` is: handle_exception_irqoff vmx_handle_exit_irqoff kvm_x86_handle_exit_irqoff vcpu_enter_guest [1] https://lore.kernel.org/all/20221213060912.654668-8-seanjc@xxxxxxxxxx/ Signed-off-by: Tianyi Liu <i.pear@xxxxxxxxxxx> --- arch/x86/kvm/vmx/vmx.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index df461f387e20..3a0b13867a6b 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6955,6 +6955,12 @@ static void handle_exception_irqoff(struct vcpu_vmx *vmx) /* Handle machine checks before interrupts are enabled */ else if (is_machine_check(intr_info)) kvm_machine_check(); + /* We need to handle NMIs before interrupts are enabled */ + else if (is_nmi(intr_info)) { + kvm_before_interrupt(&vmx->vcpu, KVM_HANDLING_NMI); + vmx_do_nmi_irqoff(); + kvm_after_interrupt(&vmx->vcpu); + } } static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu) @@ -7251,13 +7257,6 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu, else vmx->exit_reason.full = vmcs_read32(VM_EXIT_REASON); - if ((u16)vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI && - is_nmi(vmx_get_intr_info(vcpu))) { - kvm_before_interrupt(vcpu, KVM_HANDLING_NMI); - vmx_do_nmi_irqoff(); - kvm_after_interrupt(vcpu); - } - guest_state_exit_irqoff(); } -- 2.41.0
