This RFC proposes an integration of "ARM: Forwarding physical interrupts to a guest VM" (http://lwn.net/Articles/603514/) in KVM. It enables to transform a VFIO platform driver IRQ into a forwarded IRQ. The direct benefit is that, for a level sensitive IRQ, a VM switch can be avoided on guest virtual IRQ completion. Before this patch, a maintenance IRQ was triggered on the virtual IRQ completion. When the IRQ is forwarded, the VFIO platform driver does not need to disable the IRQ anymore. Indeed when returning from the IRQ handler the IRQ is not deactivated. Only its priority is lowered. This means the same IRQ cannot hit before the guest completes the virtual IRQ and the GIC automatically deactivates the corresponding physical IRQ. 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 this latter becomes "transparent". The current integration is based on an extension of the KVM-VFIO device, previously used by KVM to interact with VFIO groups. The patch serie now enables KVM to directly interact with a VFIO platform device. The VFIO external API was extended for that purpose. Th KVM-VFIO device can get/put the vfio platform device, check its integrity and type, get the IRQ number associated to an IRQ index. The KVM-VFIO is extended with an architecture specific implementation. IRQ forward control is implemented in the ARM specific part. from a user point of view, the functionality is provided through new KVM-VFIO device commands, KVM_DEV_VFIO_DEVICE_(DE)ASSIGN_IRQ and the capability can be checked with KVM_HAS_DEVICE_ATTR. Assignment can only be changed when the physical IRQ is not active. It is the responsability of the user to do this check. This patch serie has the following dependencies: - "ARM: Forwarding physical interrupts to a guest VM" (http://lwn.net/Articles/603514/) in - [PATCH v2] irqfd for ARM which itself depends on - arm/arm64: KVM: Various VGIC cleanups and improvements http://lists.infradead.org/pipermail/linux-arm-kernel/2014-June/263685.html - and obviously the VFIO platform driver serie: [RFC PATCH v6 00/20] VFIO support for platform devices on ARM https://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg103247.html Integrated pieces can be found at git://git.linaro.org/people/eric.auger/linux.git on branch 3.17rc1_forward_integ_v0 This was was tested on Calxeda Miday, assigning the xgmac main IRQ. Eric Auger (9): KVM: ARM: VGIC: fix multiple injection of level sensitive forwarded IRQ KVM: ARM: VGIC: add forwarded irq rbtree lock VFIO: platform: handler tests whether the IRQ is forwarded KVM: KVM-VFIO: update user API to program forwarded IRQ VFIO: Extend external user API KVM: KVM-VFIO: allow arch specific implementation KVM: KVM-VFIO: add new VFIO external API hooks KVM: KVM-VFIO: add kvm_vfio_arch_data and accessors KVM: KVM_VFIO: ARM: implement irq forwarding control Documentation/virtual/kvm/devices/vfio.txt | 25 ++ arch/arm/include/asm/kvm_host.h | 16 + arch/arm/include/uapi/asm/kvm.h | 6 + arch/arm/kvm/Makefile | 2 +- arch/arm/kvm/kvm_vfio_arm.c | 599 +++++++++++++++++++++++++++++ drivers/vfio/platform/vfio_platform_irq.c | 7 +- drivers/vfio/vfio.c | 35 ++ include/kvm/arm_vgic.h | 1 + include/linux/kvm_host.h | 30 ++ include/linux/vfio.h | 4 + include/uapi/linux/kvm.h | 3 + virt/kvm/arm/vgic.c | 55 ++- virt/kvm/vfio.c | 92 +++++ 13 files changed, 862 insertions(+), 13 deletions(-) create mode 100644 arch/arm/kvm/kvm_vfio_arm.c -- 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
