Stephane Eranian wrote: > Hello, > > Looking at kvm-26, it seems that the CPUID values as seen by the guest OS > are still hardcoded for i386/x86-64 at least. > > For performance counter virtualization, the guest needs to see the *actual* > family/model information in order to correctly program the counters. > > It would be fairly simple to grab that information from /proc/cpuinfo > at init time in qemu. > > However, I am wondering if there would be side effects of using the > actual CPUID which could cause troubles to KVM or the guest. > >
The main issue is migration (and save/restore). If you migrate to a host with fewer capabilities, applications may fail when they use unavailable instructions that they successfully detected earlier. I think the best solution is to default to the host's capabilities, but allow command line switches to override them. This way a management application in a server farm can set a site-wide least common denominator, while a home user can enjoy the latest and greatest instructions on their machine. Upstream qemu already has a -cpu (or similar) switch for non-x86; we can probably use that. (there's another possible issue - some future features may require support from the hypervisor - that may conflict with defaulting to to the host feature set. maybe kvm should mask out any unknown features) -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
