3 preempted variables in kvm

Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> · Fri, 22 Jan 2021 23:11:08 +0800

Hi All,

I am newbie on KVM side, so probably I am wrong on the following.
Please correct me if it is.

There are 3 preempted variables in kvm:
     1, kvm_vcpu.preempted  in include/linux/kvm_host.h
     2, kvm_steal_time.preempted 3, kvm_vcpu_arch.st.preempted in arch/x86
Seems all of them are set or cleared at the same time. Like,

vcpu_put:
        kvm_sched_out()-> set 3 preempted
                kvm_arch_vcpu_put():
                        kvm_steal_time_set_preempted

vcpu_load:
        kvm_sched_in() : clear above 3 preempted
                kvm_arch_vcpu_load() -> kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
                request dealed in vcpu_enter_guest() -> record_steal_time

Except the 2nd one reuse with KVM_FEATURE_PV_TLB_FLUSH bit which could be used
separately, Could we combine them into one, like just bool kvm_vcpu.preempted? and 
move out the KVM_FEATURE_PV_TLB_FLUSH. Believe all arch need this for a vcpu overcommit.

Thanks
Alex