On 23/12/2014 16:14, Boris Ostrovsky wrote: >> + do { >> + version = pvti->version; >> + >> + /* This is also a read barrier, so we'll read version first. */ >> + rdtsc_barrier(); >> + tsc = __native_read_tsc(); > > > This will cause VMEXIT on Xen with TSC_MODE_ALWAYS_EMULATE which is > used, for example, after guest migrated (unless HW is capable of scaling > TSC rate). So does the __pvclock_read_cycles this is replacing (via pvclock_get_nsec_offset). 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