On Wed, 25 May 2016 15:45:53 +0200 Radim Krčmář <rkrcmar@xxxxxxxxxx> wrote: > 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()? Yes, thanks for pointing this. --jyh > > > 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
