On Mon, 2014-09-01 at 14:52 +0200, Eric Auger wrote: > 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 IRQ forward programming is architecture specific (virtual interrupt > controller programming basically). However the whole infrastructure is > kept generic. > > from a user point of view, the functionality is provided through new > KVM-VFIO device commands, KVM_DEV_VFIO_DEVICE_(UN)FORWARD_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 v3] irqfd for ARM > - 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 > ssh://git.linaro.org/people/eric.auger/linux.git > on branch 3.17rc3_irqfd_forward_integ_v2 > > This was was tested on Calxeda Midway, assigning the xgmac main IRQ. > > v1 -> v2: > - forward control is moved from architecture specific file into generic > vfio.c module. > only kvm_arch_set_fwd_state remains architecture specific > - integrate Kim's patch which enables KVM-VFIO for ARM > - fix vgic state bypass in vgic_queue_hwirq > - struct kvm_arch_forwarded_irq moved from arch/arm/include/uapi/asm/kvm.h > to include/uapi/linux/kvm.h > also irq_index renamed into index and guest_irq renamed into gsi > - ASSIGN/DEASSIGN renamed into FORWARD/UNFORWARD > - vfio_external_get_base_device renamed into vfio_external_base_device > - vfio_external_get_type removed > - kvm_vfio_external_get_base_device renamed into kvm_vfio_external_base_device > - __KVM_HAVE_ARCH_KVM_VFIO renamed into __KVM_HAVE_ARCH_KVM_VFIO_FORWARD > > Eric Auger (8): > 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: add new VFIO external API hooks > KVM: KVM-VFIO: generic KVM_DEV_VFIO_DEVICE command and IRQ forwarding > control > KVM: KVM-VFIO: ARM forwarding control > > Kim Phillips (1): > ARM: KVM: Enable the KVM-VFIO device > > Documentation/virtual/kvm/devices/vfio.txt | 26 ++ > arch/arm/include/asm/kvm_host.h | 7 + > arch/arm/kvm/Kconfig | 1 + > arch/arm/kvm/Makefile | 4 +- > arch/arm/kvm/kvm_vfio_arm.c | 85 +++++ > drivers/vfio/platform/vfio_platform_irq.c | 7 +- > drivers/vfio/vfio.c | 24 ++ > include/kvm/arm_vgic.h | 1 + > include/linux/kvm_host.h | 27 ++ > include/linux/vfio.h | 3 + > include/uapi/linux/kvm.h | 9 + > virt/kvm/arm/vgic.c | 59 +++- > virt/kvm/vfio.c | 497 ++++++++++++++++++++++++++++- > 13 files changed, 733 insertions(+), 17 deletions(-) > create mode 100644 arch/arm/kvm/kvm_vfio_arm.c > Have we ventured too far in the other direction? I suppose what I was hoping to see was something more like: case KVM_DEV_VFIO_DEVICE_FORWARD_IRQ:{ /* get vfio_device */ /* get mutex */ /* verify device+irq isn't already forwarded */ /* allocate device/forwarded irq */ /* get struct device */ /* callout to arch code passing struct device, gsi, ... */ /* if success, add to kv, else free and error */ /* mutex unlock */ } Exposing the internal mutex out to arch code, as in v1, was an indication that we were pushing too much out to arch code, but including platform_device.h into virt/kvm/vfio.c tells me we're still not abstracting at the right point. Thanks, Alex -- 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
