On Thu, Mar 22, 2007 at 12:06:32PM +0200, Avi Kivity wrote: > Joerg Roedel wrote: > >On Thu, Mar 22, 2007 at 09:38:12AM +0200, Avi Kivity wrote: > > > >>Joerg Roedel wrote: > >> > >>>From: Joerg Roedel <[EMAIL PROTECTED]> > >>> > >>>This patch forbids the guest to execute monitor/mwait instructions on > >>>SVM. This is necessary because the guest can execute these instructions > >>>if they are available even if the kvm cpuid doesn't report its > >>>existence. > >>> > >>> > >>You're intercepting the instructions unconditionally. What about the case > >>where cpuid does > >>report monitor/mwait support? The guest can legitimately use them then. > >> > > > >I prepared a patch for QEmu to handle this but finally not > >submitted it because QEmu does not set the Monitor bit anyway. But you > >are right. It is possible for userspace to set the Montior bit and the > >guest won't be able to use it. > >I think an architecture dependent cpuid mask feature in the kernel would > >solve this problem. I'll prepare a patch for that. > > > > > > I think I'm misunderstanding something. > > Is there actually an AMD cpu that supports monitor/mwait? If not > (understandably, having no
Yes, the family 10h processors have support for that. > hyperthreading), then wouldn't executing monitor or mwait generate #UD > anyway? I don't think > there's need for the cpuid mask as long as setting the monitor bit cannot > endanger the > kernel. 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. 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
