On 08/07/20 17:45, Sean Christopherson wrote: > On Wed, Jul 08, 2020 at 05:31:14PM +0200, Paolo Bonzini wrote: >> The order follows the SDM. I'm tempted to remove the CR0 check >> altogether, since non-protected-mode always runs at CPL0 AFAIK, but let's >> keep it close to what the manual says. > > Heh, it wouldn't surprise me in the least if there's a way to get the SS > arbyte to hold a non-zero DPL in real mode :-). I'm not sure if SMM lets you set non-zero SS.DPL in real mode. It's one of the few things that are checked with unrestricted guest mode so there's hope; on the other hand I know for sure that in the past RSM could get you to VM86 mode with CPL=0, while in VMX it causes vmentry to fail. It would be an interesting testcase to write for KVM, to see if you get a vmentry failure after you set the hidden AR bytes that way and RSM... Paolo
