On Thu, Jan 21, 2010 at 07:47:22AM -0800, H. Peter Anvin wrote: > On 01/21/2010 01:02 AM, Avi Kivity wrote: > >> > >> You can also just emulate the state transition -- since you know > >> you're dealing with a flat protected-mode or long-mode OS (and just > >> make that a condition of enabling the feature) you don't have to deal > >> with all the strange combinations of directions that an unrestricted > >> x86 event can take. Since it's an exception, it is unconditional. > > > > Do you mean create the stack frame manually? I'd really like to avoid > > that for many reasons, one of which is performance (need to do all the > > virt-to-phys walks manually), the other is that we're certain to end up > > with something horribly underspecified. I'd really like to keep as > > close as possible to the hardware. For the alternative approach, see Xen. > > > > I obviously didn't mean to do something which didn't look like a > hardware-delivered exception. That by itself provides a tight spec. > The performance issue is real, of course. > > Obviously, the design of VT-x was before my time at Intel, so I'm not > familiar with why the tradeoffs that were done they way they were. > Is it so out of question to reserver exception below 32 for PV use? -- Gleb. -- 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
