On Sun, Dec 16, 2007 at 01:32:40PM +0200, Avi Kivity wrote: > Dong, Eddie wrote: > > > BTW, do we need to support live migrating an AMD VM to Intel platform or > > vice versa > > Yes, it allows users to buy the machines with the best cost/performance > ratio, rather than continue to buy machines from the same vendor all the > time.
I don't agree with this. A user can still buy machines from both vendors and migrate offline it he wants to. In general I think that allowing live migration between Intel and AMD hosts is not a good idea because you limit the guest to the subset of the CPU features available on both platforms. This disallows many optimizations and costs performance for the guest. Take the problem Dor mentioned this week about the performance impact of the gettimeofday() syscall causing many cpuid guest exits. If we had not to support migration between AMD and Intel we could simply propagate FEATURE_RDTSCP to an guest on AMD an SYNC_RDTSC on Intel platforms. The Linux get_cycles_sync() function would then no longer execute CPUID. This is only one example, I found some more during my work on KVM. Joerg -- | AMD Saxony Limited Liability Company & Co. KG Operating | Wilschdorfer Landstr. 101, 01109 Dresden, Germany System | Register Court Dresden: HRA 4896 Research | General Partner authorized to represent: Center | AMD Saxony LLC (Wilmington, Delaware, US) | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy ------------------------------------------------------------------------- SF.Net email is sponsored by: Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel