On 01/27/2010 11:36 AM, Michael S. Tsirkin wrote: > > >> smp_mb() is used for processor-vs-processor ordering, which can't happen >> on UP systems, but for process-vs-device, we must use mb(). >> >> (this shows up if running a UP guest on an SMP host). >> > Currently, yes. But virtio is not a real device. > Here's what I was really trying to improve: rmb() is an lfence on > x86_64, but smp_rmb() is a barrier() and this is really sufficient for > virtio because x86_64 does not reorder memory reads. > > x86_64 can do speculative and reordered reads. > Does this mean such an optimization would need a new macro? > Please no. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
