Re: [PATCH] KVM: VMX: switch to hrtimer for TSC deadline timer when L2 guest is running

[Paolo Bonzini]

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.

Paolo