2016-07-07 18:33 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>: > > > On 07/07/2016 10:31, Wanpeng Li wrote: >> 2016-07-07 16:10 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>: >>> >>> >>> On 07/07/2016 05:46, Wanpeng Li wrote: >>>> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx> >>>> >>>> We will go to vcpu_run() loop after L0 emulates VMRESUME which incurs >>>> kvm_sched_out and kvm_sched_in operations since cond_resched() will be >>>> called once need resched. Preemption timer will be reprogrammed if vCPU >>>> is scheduled to a different pCPU. Then the preemption timer bit of vmcs02 >>>> will be set if L0 enable preemption timer to run L1 even if L1 doesn't >>>> enable preemption timer to run L2. >>>> >>>> This patch fix it by don't reprogram preemption timer of vmcs02 if L1's >>>> vCPU is scheduled on diffent pCPU when we are in the way to vmresume >>>> nested guest. >>> >>> Again, this is wrong. There is no reason why L1's APIC timer cannot be >>> emulated through the vmcs12's preemption timer setting. The only issue >>> is getting the pin-based execution controls right. >> >> This patch doesn't intend to implement "L1 TSC deadline timer to >> trigger while L2 is running", it just solves why vmcs02 is set even if >> >> exec_control = vmcs12->pin_based_vm_exec_control; >> exec_control |= vmcs_config.pin_based_exec_ctrl; >> exec_control &= ~PIN_BASED_VMX_PREEMPTION_TIMER; >> >> We should set pin-based execution controls right to implement "L1 TSC >> deadline timer to trigger while L2 is running". > > Ok, now I get it, but I still cannot understand the logic in your patch. > > You write: > > if (!is_guest_mode(vcpu) && > kvm_lapic_hv_timer_in_use(vcpu) && > kvm_x86_ops->set_hv_timer(vcpu, > kvm_get_lapic_tscdeadline_msr(vcpu))) > kvm_lapic_switch_to_sw_timer(vcpu); > > but this means that while L2 runs you miss L1's APIC timer interrupt. Do you > want this instead: > > if (kvm_lapic_hv_timer_in_use(vcpu) && > (is_guest_mode(vcpu) || > kvm_x86_ops->set_hv_timer(vcpu, > kvm_get_lapic_tscdeadline_msr(vcpu)))) > kvm_lapic_switch_to_sw_timer(vcpu); Nice point out. :) I will send out another version. Regards, Wanpeng Li -- 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
