On 07/08/2017 10:44, Longpeng(Mike) wrote: > + > + /* > + * Intel sdm vol3 ch-25.1.3 says: The “PAUSE-loop exiting” > + * VM-execution control is ignored if CPL > 0. So the vcpu > + * is always exiting with CPL=0 if it uses PLE.
This is not true (how can it be?). What 25.1.3 says is, the VCPU is always at CPL=0 if you get a PAUSE exit (reason 40) and PAUSE exiting is 0 (it always is for KVM). But here you're looking for a VCPU that didn't get a PAUSE exit, so the CPL can certainly be 3. However, I understand that vmx_get_cpl can be a bit slow here. You can actually read SS's access rights directly in this function and get the DPL from there, that's going to be just a single VMREAD. The only difference is when vmx->rmode.vm86_active=1. However, pause-loop exiting is not working properly anyway if vmx->rmode.vm86_active=1, because CPL=3 according to the processor. Paolo > + * The following block needs less cycles than vmx_get_cpl(). > + */ > + if (cpu_has_secondary_exec_ctrls()) > + secondary_exec_ctrl = vmcs_read32(SECONDARY_VM_EXEC_CONTROL); > + if (secondary_exec_ctrl & SECONDARY_EXEC_PAUSE_LOOP_EXITING) > + return true; > + Paolo
