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. 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
