On 03/08/2015 12:23, Zhang, Yang Z wrote: > > In any case, the TMR behavior introduced by the APICv patches is > > completely different from the hardware behavior, so it has to be fixed. > > But any real problem with it? It is a problem for split irqchip, where the EOI exit bitmap can be inferred from the IOAPIC routes but the TMR cannot. The hardware behavior on the other hand can be implemented purely within the LAPIC. > > The alternative is to inject level-triggered interrupts > > synchronously, without using posted interrupts. > > > > I'll write some testcases to understand the functioning of TMR in the > > virtual-APIC page, but the manual seems clear to me. > > Currently, no existing hardware will use TMR and will not cause any > problem.(That's the reason why we leave it in Xen).But we don't know > whether future hardware will use it or not(SDM always keeps changing > :)). But that would be covered by a different execution control (for backwards compatibility). We'll get there when such a feature is introduced. > And per 24.11.4's description, the perfect solution is don't > modify it. btw, IIRC, only TMR doesn't follow the rule. All other > VMCS accesses are issued in right VMCS context. Yes, that's correct. It's just the TMR. 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
