Second try to allow adaptive interrupt handlers according to the line's current sharing situation. This one converts the explicit notifier interface into several extension of existing genirq APIs: - introduce a interrupt status word that can be read by interrupt handlers to obtain the current line sharing state - introduce IRQF_ADAPTIVE: handlers registered with this flag will be informed about an upcoming line sharing by calling the interrupt handler itself (instead of a notifier callback) - introduce IRQF_COND_ONESHOT: IRQF_ONESHOT semantics if the line is not shared, standard semantics otherwise (removes the need to re-register handlers to switch between IRQF_SHARED and IRQF_ONESHOT) The result may look simpler on first glance than v1, but it comes with more subtle race scenarios IMO. I thought them through, hopefully catching all, but I would appreciate any skeptical review. I also tried to replace line-level disabling from the interrupt handler with signaling genirq to keep the line masked on handler return. However, I finally dropped this idea as it turns out to be very hard (if not impossible) to properly synchronize the generic tail (in genirq) with the driver that may want to re-enable the line at the same time (depending on the driver's internal state). But if anyone sees a magically simple way to achieve this, I'm still all ears. Finally, the last patch in this series makes use of the new interface for KVM's PCI pass-through subsystem. KVM has to keep the interrupt source disabled while calling into the guest to handle the event. This can be done at device or line level. The former is required to share the interrupt line, the latter is an order of magnitude faster. Beside pass-through support of KVM, further users of this new interface could become VFIO (not yet mainline) and uio_pci_generic which have to resolve the same conflict. Note: The KVM patch depends on http://thread.gmane.org/gmane.comp.emulators.kvm.devel/64515 Jan Kiszka (4): genirq: Introduce driver-readable IRQ status word genirq: Inform handler about line sharing state genirq: Add support for IRQF_COND_ONESHOT KVM: Allow host IRQ sharing for passed-through PCI 2.3 devices Documentation/kvm/api.txt | 27 ++++ arch/x86/kvm/x86.c | 1 + include/linux/interrupt.h | 15 ++ include/linux/irq.h | 2 + include/linux/irqdesc.h | 2 + include/linux/kvm.h | 6 + include/linux/kvm_host.h | 10 ++- kernel/irq/irqdesc.c | 2 + kernel/irq/manage.c | 74 ++++++++++- virt/kvm/assigned-dev.c | 336 ++++++++++++++++++++++++++++++++++++++++----- 10 files changed, 437 insertions(+), 38 deletions(-) -- 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
