This series allows to set ARM IRQ forwarding between a VFIO platform device physical IRQ and a guest virtual IRQ. The link is coordinated by the IRQ bypass manager. The principle is the VFIO platform driver registers an IRQ bypass producer struct on VFIO_IRQ_SET_ACTION_TRIGGER while KVM irqfd registers a consumer struct on the irqfd assignment. This leads to a handshake based on the eventfd context (used as token) match. When either of the producer/consumer disappears, an unregistration occurs and the link is disconnected. This kernel integration deprecates the former kvm-vfio approach: https://lkml.org/lkml/2015/4/13/353. Some rationale about that change can be found in IRQ bypass manager thread: https://lkml.org/lkml/2015/6/29/268 Dependencies: 1- [PATCH v4 00/11] arm/arm64: KVM: Active interrupt state switching for shared devices (http://www.spinics.net/lists/arm-kernel/msg437884.html) except PATCH 11 2- [PATCH 0/6] irqchip: GICv2/v3: Add support for irq_vcpu_affinity 3- [PATCH v4] virt: IRQ bypass manager (https://lkml.org/lkml/2015/8/6/526) 4- [PATCH 0/2] KVM: arm/arm64: Guest synchronous halt/resume (https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg950942.html) All those pieces can be found at: https://git.linaro.org/people/eric.auger/linux.git/shortlog/refs/heads/v4.2-rc6-irq-forward-v3 More backgroung on ARM IRQ forwarding in the text below and at http://www.linux-kvm.org/images/a/a8/01x04-ARMdevice.pdf. A forwarded IRQ is deactivated by the guest and not by the host. When the guest deactivates the associated virtual IRQ, the interrupt controller automatically completes the physical IRQ. Obviously this requires some HW support in the interrupt controller. This is the case for ARM GICv2. The direct benefit is that, for a level sensitive IRQ, a VM exit can be avoided on forwarded IRQ completion. When the IRQ is forwarded, the VFIO platform driver does not need to mask the physical IRQ anymore before signaling the eventfd. Indeed genirq lowers the running priority, enabling other physical IRQ to hit except that one. Besides, the injection still is based on irqfd triggering. The only impact on irqfd process is resamplefd is not called anymore on virtual IRQ completion since deactivation is not trapped by KVM. This was tested on Calxeda Midway, assigning the xgmac main IRQ History: v2 (RFC) -> v3(PATCH): - all dependencies now have a patch status - we dropped the producer active boolean exchanged between the VFIO producer and irqfd arm consumer. As a consequence, on unforward, if the IRQ is active, this latter is deactivated without VFIO-masking it. So we do not exactly come back to the exact state where we would be in unforwarded state. A new physical IRQ can hit while the previous virtual IRQ is under treatment. Its injection in the guest may be rejected thanks to the VGIC state machine. This IRQ will be lost but I don't think this is a severe issue. In case no new IRQ hits, the guest deactivation of the virtual IRQ will trigger the resamplefd which will VFIO unmask the non-masked IRQ. This also has no consequence. - VFIO platform driver consumer_add now can fail. It rejects the transition for forwarding state in case the IRQ is active - the series is rebased on new irq_vcpu_affinity series - no dependency anymore on "chip/vgic adaptations for forwarded irq" which was partially integrated into Marc's series. A fix is still needed through. - Guest synchronous halt/resume patch re-integrated into this series - integrate a new patch file coming mixing [PATCH v4 11/11] KVM: arm/arm64: vgic: Allow HW interrupts for non-shared devices & [RFC v2 2/4] KVM: arm: vgic: fix state machine for forwarded IRQ v1 -> v2: - irq bypass manager and irqfd consumer moved in a separate patch - kvm_arm_[halt,resume]_guest moved in a separate patch - remove VFIO external functions since we do not need them anymore - apply container_of strategy advised by Paolo. Only active field remains and discussions will tell whether we get rid of it. - renamed kvm_arch functions - kvm-vfio v6 -> RFC v1 based on IRQ bypass manager see previous history in https://lkml.org/lkml/2015/4/13/353). Best Regards Eric Eric Auger (9): VFIO: platform: registration of a dummy IRQ bypass producer VFIO: platform: test forwarded state when selecting the IRQ handler VFIO: platform: single handler using function pointer VFIO: platform: add vfio_platform_set_automasked VFIO: platform: add vfio_platform_is_active VFIO: platform: add irq bypass producer management KVM: arm/arm64: vgic: support irqfd injection of a forwarded IRQ KVM: arm/arm64: vgic: forwarding control KVM: arm/arm64: implement IRQ bypass consumer functions Marc Zyngier (1): KVM: arm/arm64: vgic: Allow HW interrupts for non-shared devices arch/arm/kvm/Kconfig | 1 + arch/arm/kvm/arm.c | 35 +++++ arch/arm64/kvm/Kconfig | 1 + drivers/vfio/platform/vfio_platform_irq.c | 113 +++++++++++++- drivers/vfio/platform/vfio_platform_private.h | 4 + include/kvm/arm_vgic.h | 12 +- virt/kvm/arm/arch_timer.c | 3 +- virt/kvm/arm/vgic.c | 215 ++++++++++++++++++++++++-- 8 files changed, 358 insertions(+), 26 deletions(-) -- 1.9.1 -- 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
