Hi, On 12/06/2019 10:08, Zenghui Yu wrote: > Currently, we use trace_kvm_exit() to report exception type (e.g., > "IRQ", "TRAP") and exception class (ESR_ELx's bit[31:26]) together. (They both caused an exit!) > But hardware only saves the exit class to ESR_ELx on synchronous EC is the 'Exception Class'. Exit is KVM/Linux's terminology. > exceptions, not on asynchronous exceptions. When the guest exits > due to external interrupts, we will get tracing output like: > > "kvm_exit: IRQ: HSR_EC: 0x0000 (UNKNOWN), PC: 0xffff87259e30" > > Obviously, "HSR_EC" here is meaningless. I assume we do it this way so there is only one guest-exit tracepoint that catches all exits. I don't think its a problem if user-space has to know the EC isn't set for asynchronous exceptions, this is a property of the architecture and anything using these trace-points is already arch specific. > This patch splits "exit" and "trap" events by adding two tracepoints > explicitly in handle_trap_exceptions(). Let trace_kvm_exit() report VM > exit events, and trace_kvm_trap_exit() report VM trap events. > > These tracepoints are adjusted also in preparation for supporting > 'perf kvm stat' on arm64. Because the existing tracepoints are ABI, I don't think we can change them. We can add new ones if there is something that a user reasonably needs to trace, and can't be done any other way. What can't 'perf kvm stat' do with the existing trace points? > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > index 516aead..af3c732 100644 > --- a/arch/arm64/kvm/handle_exit.c > +++ b/arch/arm64/kvm/handle_exit.c > @@ -264,7 +264,10 @@ static int handle_trap_exceptions(struct kvm_vcpu *vcpu, struct kvm_run *run) > exit_handle_fn exit_handler; > > exit_handler = kvm_get_exit_handler(vcpu); > + trace_kvm_trap_enter(vcpu->vcpu_id, > + kvm_vcpu_trap_get_class(vcpu)); > handled = exit_handler(vcpu, run); > + trace_kvm_trap_exit(vcpu->vcpu_id); > } Why are there two? Are you using this to benchmark the exit_handler()? As we can't remove the EC from the exit event, I don't think this tells us anything new. > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > index 90cedeb..9f63fd9 100644 > --- a/virt/kvm/arm/arm.c > +++ b/virt/kvm/arm/arm.c > @@ -758,7 +758,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > /************************************************************** > * Enter the guest > */ > - trace_kvm_entry(*vcpu_pc(vcpu)); > + trace_kvm_entry(vcpu->vcpu_id, *vcpu_pc(vcpu)); Why do you need the PC? It was exported on exit. (its mostly junk for user-space anyway, you can't infer anything from it) Thanks, James
