> > > > @@ -10727,8 +10732,14 @@ static void nested_vmx_vmexit(struct > > > > kvm_vcpu *vcpu, u32 exit_reason, > > > > load_vmcs12_host_state(vcpu, vmcs12); > > > > > > > > - /* Update TSC_OFFSET if TSC was changed while L2 ran */ > > > > + /* Update any VMCS fields that might have changed while > > > > L2 ran */ vmcs_write64(TSC_OFFSET, vmx->nested.vmcs01_tsc_offset); > > > > + if (vmx->hv_deadline_tsc == -1) > > > > + vmcs_clear_bits(PIN_BASED_VM_EXEC_CONTROL, > > > > + PIN_BASED_VMX_PREEMPTION_TIMER); > > > > + else > > > > + vmcs_set_bits(PIN_BASED_VM_EXEC_CONTROL, > > > > + PIN_BASED_VMX_PREEMPTION_TIMER); > > > > > > Why do we need change the vmcs01 here? Per my understanding, the > > > vmcs01 is not changed when the L2 guest is running thus the > > > PIN_BASED_VM_EXEC_CONTROL should not be changed? > > > > This is the point where we are updating the vmcs01 after exiting. If > > vmx->hv_deadline_tsc has changed (for example because of a preemption > > Thanks for the explaination. I try to go through the code and still > have one question. I'd describe below and hope get your input. > > When the L2 guest running while the VMX Preemption timer triggered, the > vcpu_enter_guest() will trigger vmx_handle_exit(), with the CPU vmcs as > vmcs02. On the vmx_handle_exit(), the nested_vmx_exit_handled() return > false as the 1st patch did, thus the vmcs is not switched. The > kvm_lapic_expired_hv_timer() will be called with vmcs02, instead of > vmcs01. Is it something we wanted? I assume we should use vmcs01 there > since we will clear the preemption timer VMCS bit there. Actually we want both. For whatever reason, the interrupt might not cause a vmexit---for example if the L0 PPR is masking the LVTT vector. In this case, we need to cancel the preemption timer in the vmcs02 (done by kvm_lapic_expired_hv_timer) and keep running L2. On the next vmexit, nested_vmx_vmexit will load the vmcs01 and clear the preemption timer bit. Of course this is only theory until Wanpeng confirms that my patch works for him. :) Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
