On 07/06/16 16:01, Haozhong Zhang wrote: > On 07/06/16 09:46, Paolo Bonzini wrote: > > > > > > On 06/07/2016 08:05, Haozhong Zhang wrote: > > >> > > > >> > Nested preemption timer is emulated by hrtimer, so it doesn't > > >> > influence vmcs02, why this is needed? > > > Nested (L2) preemption timer is not affected for sure, and this patch > > > is to fix another problem caused by using L1 preemption timer for L1 > > > TSC deadline timer. When we use L1 VMX preemption timer for L1 TSC > > > deadline timer, we intend to use the pin-based exec config and the VMX > > > preemption timer value in vmcs01. However, when L2 guest is running, > > > vmcs02 is loaded as the current VMCS so that a different VMX > > > preemption timer config is used (i.e. VMX preemption timer is disabled > > > in prepare_vmcs02()). If we still use preemption timer for L1 TSC > > > deadline timer at this moment, then L1 TSC deadline timer will not be > > > able to be triggered when L2 guest is running. > > > > The right fix then is to set the pin-based controls in prepare_vmcs02, > > based on vcpu->arch.hv_deadline_tsc. > > Then KVM needs to distinguish L1 and L2 VMEXITs for preemption timer > (or does KVM already have this?). The current implementation which > uses a separate hrtimer for L2 preemption timer can easily distinguish > them. > And L1 hypervisor may also want to use preemption timer for L2 guest. In this case, L0 KVM can not reuse preemption timer for both L1 and L2. Haozhong -- 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
