On Thu, Mar 22, 2007 at 12:42:28PM +0200, Avi Kivity wrote: > Joerg Roedel wrote: > >There is no danger for the host kernel but for the guest. If the > >userspace sets the monitor bit the guest will receive an #UD when trying > >to use it. And we don't want the guest to use it because it is not > >virtualized yet. > > > > So, isn't a simpler fix not to set the monitor bit in cpuid? > > The patch is correct, but I don't see why it's needed as any guest will check > the cpuid bit > before using monitor.
Right. But it is possible for userspace to enable monitor bit for the guest. Without virtualization of these 2 instructions the guest would idle in the guest state after calling mwait and prevent other processes and guests from running in that time. I don't think this is acceptable. And if we disable this bit in cpuid we should also prevent the guest from executing it to emulate the behavior of a real cpu in host mode. So I agree we should mask the cpuid monitor bit. The savest way to do so is in the kvm-amd module imho. And, also imho, we should the guest really forbid to execute it. Joerg -- Joerg Roedel Operating System Research Center AMD Saxony LLC & Co. KG ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
