On 2011-10-24 11:45, Avi Kivity wrote: > On 10/21/2011 11:19 AM, Jan Kiszka wrote: >> Currently, MSI messages can only be injected to in-kernel irqchips by >> defining a corresponding IRQ route for each message. This is not only >> unhandy if the MSI messages are generated "on the fly" by user space, >> IRQ routes are a limited resource that user space as to manage >> carefully. > > By itself, this does not provide enough value to offset the cost of a > new ABI, especially as userspace will need to continue supporting the > old method for a very long while. Yes, but less sophistically as it would now. > >> By providing a direct injection with, we can both avoid using up limited >> resources and simplify the necessary steps for user land. The API >> already provides a channel (flags) to revoke an injected but not yet >> delivered message which will become important for in-kernel MSI-X vector >> masking support. >> > > With the new feature it may be worthwhile, but I'd like to see the whole > thing, with numbers attached. It's not a performance issue, it's a resource limitation issue: With the new API we can stop worrying about user space device models consuming limited IRQ routes of the KVM subsystem. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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
