On 2012-10-25 18:23, Avi Kivity wrote: > On 10/25/2012 03:34 PM, Jan Kiszka wrote: > >>>> Second, it clearly shows that we need to address lock-less IRQ delivery. >>>> Almost nothing is won if we have to take the global lock again to push >>>> an IRQ event to the guest. I'm repeating myself, but the problem to be >>>> solved here is almost identical to fast IRQ delivery for assigned >>>> devices (which we only address pretty ad-hoc for PCI so far). >>>> >>> Interesting, could you show me more detail about it, so I can google... >> >> No need to look that far, just grep for pci_device_route_intx_to_irq, >> pci_device_set_intx_routing_notifier and related functions in the code. > > We can address it in the same way the memory core supports concurrency, > by copying dispatch information into rcu or lock protected data structures. > > But I really hope we can avoid doing it now.
I doubt so as the alternative is taking the BQL while (still) holding the device lock. But that creates ABBA risks. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux
