Il 03/06/2013 18:40, Gleb Natapov ha scritto: >> > Won't work, vmx won't let you enter in such a configuration. > > Why? It is possible to have NULL descriptor in 32bit mode with vmx. But > we do not usually intercept #GP while executing 32bit mode, so we will > have to track if there is artificial NULL selector and enables #GP > interception and then emulate on every #GP. Yes, that's what I had in mind. Of course for invalid CS you do have to emulate. >> > Maybe you can detect the exact code sequence (%eip, some instructions, >> > register state) and clear %fs and %gs. > My be we can set dpl to rpl unconditionally on a switch from 16 to 32 > bit. The only problem I can see with it is that if a guest enters user > mode without explicitly reload the segment it will be accessible by a > user mode code, but I am not sure it is well defined what dpl of a 16 > bit segment is after transition to 32 bit mode anyway, so it would be > crazy to do so. That too, or just set it to 3. But perhaps the #GP interception wouldn't be too hard. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
