On Tue, Jan 19, 2010 at 12:10:17PM -0800, H. Peter Anvin wrote: > On 01/19/2010 09:44 AM, Gleb Natapov wrote: > > > > Yes it can be done this way and I'll look into it once more. Using > > exception vector is more convenient for three reasons: it allows to pass > > additional data in error code, it doesn't require guest to issue EOI, > > exception can be injected when interrupts are disabled by a guest. The > > last one is not important for now since host doesn't inject notifications > > when interrupts are disabled currently. Having Intel allocate one > > exception vector for hypervisor use would be really nice though. > > > > That's probably not going to happen, for the rather obvious reason: *you > already have 224 of them*. > > You seem to be thinking here that vectors 0-31 have to be exceptions and > 32-255 have to be interrupts. *There is no such distinction*; the only > thing special about 0-31 is that we (Intel) reserve the right to control > the assignments; for 32-255 the platform and OS control the assignment. > I would be glad to interpret the spec like you do, but table 6-1 SDM 3A mark vectors 2,32-255 as interrupts while others are traps, fault and aborts. Unfortunately VMX designers seems to be interpreting the spec like I do. See below. > 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. 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. -- 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
