On 07/06/16 13:37, Wanpeng Li wrote: > Cc Jan, > 2016-07-06 13:10 GMT+08:00 Haozhong Zhang <haozhong.zhang@xxxxxxxxx>: > > A different VMCS is loaded when L2 guest is running, so it's incorrect > > to use the VMX preemption timer for L1 TSC deadline timer. This patch > > switches to hrtimer for L1 TSC deadline timer when entering L2 guest, > > and switches back to VMX preemption timer when nested VMEXIT from L2 to > > L1. > > 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. Thanks, 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
