Dong, Eddie wrote: > Avi Kivity wrote: > >> Dong, Eddie wrote: >> >>>> There's a two-liner required to make it work. I'll add it soon. >>>> >>>> >>>> >>> But you still needs to issue WBINVD to all pCPUs which just move >>> non-response time from one place to another, not? >>> >>> >> You don't actually need to emulate wbinvd, you can just ignore it. >> >> The only reason I can think of to use wbinvd is if you're taking a cpu >> down (for a deep sleep state, or if you're shutting it off). A guest >> need not do that. >> >> Any other reason? dma? all dma today is cache-coherent, no? >> >> > For legacy PCI device, yes it is cache-cohetent, but for PCIe devices, > it is no longer a must. A PCIe device may not generate snoopy cycle > and thus require OS to flush cache. > > For example, a guest with direct device, say audio, can copy > data to dma buffer and then wbinvd to flush cache out and ask HW > DMA to output. >
Okay. In that case the host can emulate wbinvd by using the clflush instruction, which is much faster (although overall execution time may be higher), maintaining real-time response times. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
