On Thu, Jan 28, 2010 at 10:01:09AM +1030, Rusty Russell wrote: > On Thu, 28 Jan 2010 09:12:23 am Michael S. Tsirkin wrote: > > virtio is communicating with a virtual "device" that actually runs on > > another host processor. Thus SMP barriers can be used to control > > memory access ordering. > > > > Where possible, we should use SMP barriers which are more lightweight than > > mandatory barriers, because mandatory barriers also control MMIO effects on > > accesses through relaxed memory I/O windows (which virtio does not use) > > (compare specifically smp_rmb and rmb on x86_64). > > Xen had a similar issue, in that UP guests running on SMP hosts need to issue > SMP barriers. Is this not also a requirement for virtio? Of course it is. That's why I have ifdef CONFIG_SMP and use mandatory barriers on UP. > But I'm not sure what came out of the discussion: Jeremy? > > Cheers, > Rusty. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
