On 01/21/2010 07:10 PM, Michael S. Tsirkin wrote: > Documentation/memory-barriers.txt says: > Mandatory barriers should not be used to control SMP effects, since > mandatory barriers unnecessarily impose overhead on UP systems. > > This rule applies to virtio, so let's do it correctly. > >
This is wrong. A UP guest still runs in parallel with the virtio device. 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). -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/virtualization
