On Mon, Jul 02, 2012 at 12:43:48PM +0300, Avi Kivity wrote: > On 07/02/2012 12:30 PM, Jan Kiszka wrote: > > On 2012-07-02 11:18, Michael S. Tsirkin wrote: > >> I've been thinking hard about Jan's patches for device > >> assignment. Basically while I thought it makes sense > >> to make all devices: assignment and not - behave the > >> same and use same APIs for injecting irqs, Anthony thinks there is huge > >> value in making irq propagation hierarchical and device assignment > >> should be special cased. > > > > On the long term, we will need direct injection, ie. caching, to allow > > making it lock-less. Stepping through all intermediate layers will cause > > troubles, at least performance-wise, when having to take and drop a lock > > at each stop. > > So we precalculate everything beforehand. Instead of each qemu_irq > triggering a callback, calculating the next hop and firing the next > qemu_irq, configure each qemu_irq array with a function that describes > how to take the next hop. Whenever the configuration changes, > recalculate all routes. > > For device assignment or vhost, we can have a qemu_irq_irqfd() which > converts a qemu_irq to an eventfd. If the route calculations determine > that it can be serviced via a real irqfd, they also configure it as an > irqfd. Otherwise qemu configures a poll on this eventfd and calls the > callback when needed. This is more or less what I had in mind and what Anthony objects to. > -- > error compiling committee.c: too many arguments to function > -- 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
