On Thu, Jan 21, 2010 at 11:02:19AM +0200, Avi Kivity wrote: > On 01/20/2010 07:43 PM, H. Peter Anvin wrote: > >On 01/20/2010 02:02 AM, Gleb Natapov wrote: > >> > >>>You can have the guest OS take an exception on a vector above 31 just > >>>fine; you just need it to tell the hypervisor which vector it, the OS, > >>>assigned for this purpose. > >>> > >>VMX doesn't allow to inject hardware exception with vector > >>greater then 31. > >>SDM 3B section 23.2.1.3. > >> > > > >OK, you're right. I had missed that... I presume it was done for > >implementation reasons. > > My expectation is that is was done for forward compatibility reasons. > > > > >>I can inject the event as HW interrupt on vector greater then 32 but not > >>go through APIC so EOI will not be required. This sounds > >>non-architectural > >>and I am not sure kernel has entry point code for this kind of event, it > >>has one for exception and one for interrupts that goes through > >>__do_IRQ() > >>which assumes that interrupts should be ACKed. > > > >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. > That and our event injection path can't play with guest memory right now since it is done from atomic context. -- 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
