On 07/08/2017 14:28, Longpeng(Mike) wrote: > * kvm_arch_spin_in_kernel() returns whether the vcpu (which exits due to > spinlock) is CPL=0. It only be called by kvm_vcpu_on_spin(), and the > input vcpu is 'me' which get a PAUSE exit now. * > > I split kvm_arch_vcpu_in_kernel(in RFC) into two functions: > kvm_arch_spin_in_kernel and kvm_arch_preempt_in_kernel > > Because of KVM/VMX L1 never set CPU_BASED_PAUSE_EXITING and only set > SECONDARY_EXEC_PAUSE_LOOP_EXITING if supported, so for L1: I understand better now. I think vmx.c should just return true from vmx_spin_in_kernel. However, kvm_arch_vcpu_spin_in_kernel is not necessary. Instead you should make "in_kern" an argument to kvm_vcpu_on_spin (maybe renamed to "yield_to_kernel_mode_vcpu"). Then vmx.c can just call "kvm_vcpu_on_spin(vcpu, true)". > 1. get a PAUSE exit with CPL=0 if PLE is supported > 2. never get a PAUSE exit if don't support PLE > > So, I think it can direct return true(CPL=0) if supports PLE. > > But for nested KVM/VMX(I'm not familiar with nested), it could set > CPU_BASED_PAUSE_EXITING, so I think get_cpl() is also needed. If the nested hypervisor sets CPU_BASED_PAUSE_EXITING, a PAUSE vmexit while running a nested guest would be reflected to the nested hypervisor. So you wouldn't get to handle_pause and thus to kvm_vcpu_on_spin. Thanks, Paolo
