2016-05-24 15:27-0700, Yunhong Jiang: > From: Yunhong Jiang <yunhong.jiang@xxxxxxxxx> > > Utilizing the VMX preemption timer for tsc deadline timer > virtualization. The VMX preemption timer is armed when the vCPU is > running, and a VMExit will happen if the virtual TSC deadline timer > expires. > > When the vCPU thread is scheduled out, the tsc deadline timer > virtualization will be switched to use the current solution, i.e. use > the timer for it. It's switched back to VMX preemption timer when the > vCPU thread is scheduled int. > > This solution avoids the complex OS's hrtimer system, and also the host > timer interrupt handling cost, with a preemption_timer VMexit. It fits > well for some NFV usage scenario, when the vCPU is bound to a pCPU and > the pCPU is isolated, or some similar scenario. > > However, it possibly has impact if the vCPU thread is scheduled in/out > very frequently, because it switches from/to the hrtimer emulation a lot. > > Signed-off-by: Yunhong Jiang <yunhong.jiang@xxxxxxxxx> > --- > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > static const int kvm_vmx_max_exit_handlers = > @@ -8678,6 +8684,8 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) > if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) > vmx_set_interrupt_shadow(vcpu, 0); > > + kvm_lapic_arm_hv_timer(vcpu); > + Every cycle that the host spends in root mode after setting the timeout makes the preemtion timer delayed. Can't we move the setup closer to vmlaunch, i.e. after atomic_switch_perf_msrs()? > if (vmx->guest_pkru_valid) > __write_pkru(vmx->guest_pkru); > -- 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
