On Fri, 2011-11-18 at 17:00 +0000, David Woodhouse wrote: > On Fri, 2011-11-18 at 09:03 -0700, Alex Williamson wrote: > > I can't help but thinking we're just taking the easy, lazy path for VM > > domains when it sounds like we really would prefer to keep the coherency > > set to the least common denominator of the domain rather than the > > platform. Couldn't we instead force a flush of the domain when we > > transition from coherent to non-coherent? Not sure I'm qualified to > > write that, but seems like it would keep the efficiency of VM domains > > with no effect to native DMA domains since they'd never trigger such a > > transition. The below appears as if it would work and probably be OK > > since the unnecessary cache flushes are rare, but they're still > > unnecessary... and the comments/commit log are now wrong. Thanks, > > Yeah, that would make some sense. I was about to knock up some code > which would walk the page tables and use clflush to flush every one... > but wouldn't it be saner just to use wbinvd? A bit heavy handed, but obviously easier. It feels like we could safely be more strategic, but maybe we'd end up trashing the cache anyway in a drawn out attempt to flush the context and all page tables. However, do we actually need a wbinvd_on_all_cpus()? Probably better to trash one cache than all of them. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
