On 17/11/2014 13:14, Wanpeng Li wrote: >> >>> Sorry, maybe I didn't state my question clearly. As Avi mentioned above >>> "In VMX we have VPIDs, so we only need to flush if EFER changed between >>> two invocations of the same VPID", so there is only one VPID if the >>> guest is UP, my question is if there need a TLB flush when guest's EFER >>> has been changed? >> Yes, because the meaning of the page table entries has changed. > > So both VMX EFER writes and non-VMX EFER writes cause a TLB flush for UP > guest, is there still a performance improvement in this case? Note that the guest's EFER does not change, so no TLB flush happens. The guest EFER, however, is different from the host's, so if you change it with a wrmsr in the host you will get a TLB flush on every userspace exit. Paolo -- 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
