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    SubjectRe: [PATCH v3 0/8] KVM-VFIO IRQ forward control
    On 11/24/2014 09:14 AM, Wu, Feng wrote:
    >
    >
    >> -----Original Message-----
    >> From: Eric Auger [mailto:eric.auger@linaro.org]
    >> Sent: Monday, November 24, 2014 2:36 AM
    >> To: eric.auger@st.com; eric.auger@linaro.org; christoffer.dall@linaro.org;
    >> marc.zyngier@arm.com; linux-arm-kernel@lists.infradead.org;
    >> kvmarm@lists.cs.columbia.edu; kvm@vger.kernel.org;
    >> alex.williamson@redhat.com; joel.schopp@amd.com;
    >> kim.phillips@freescale.com; paulus@samba.org; gleb@kernel.org;
    >> pbonzini@redhat.com; agraf@suse.de
    >> Cc: linux-kernel@vger.kernel.org; patches@linaro.org; will.deacon@arm.com;
    >> a.motakis@virtualopensystems.com; a.rigo@virtualopensystems.com;
    >> john.liuli@huawei.com; ming.lei@canonical.com; Wu, Feng
    >> Subject: [PATCH v3 0/8] KVM-VFIO IRQ forward control
    >>
    >> This series 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.
    >>
    >> When a physical IRQ is forwarded (to a guest), the host does not
    >> deactivates this latter. Completion ownership is transferred to the
    >> guest. When the guest deactivates the associated virtual IRQ,
    >> the interrupt controler automatically completes the physical IRQ.
    >> Obviously this requires some dedicated HW support in the interrupt
    >> controler.
    >>
    >> The direct benefit is that, for a level sensitive IRQ, it avoids a
    >> VM exit 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 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 series 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 a
    >> new KVM-VFIO group named KVM_DEV_VFIO_DEVICE and 2 associated
    >> attributes:
    >> - KVM_DEV_VFIO_DEVICE_FORWARD_IRQ,
    >> - KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ.
    >>
    >> The capability can be checked with KVM_HAS_DEVICE_ATTR.
    >>
    >> Forwarding must be activated before VFIO signaling mechanism is set
    >> using VFIO_DEVICE_SET_IRQS and unset while the signaling is disabled.
    >>
    >> ---
    >>
    >> This patch series has the following dependencies:
    >> - "ARM: Forwarding physical interrupts to a guest VM"
    >> (http://lwn.net/Articles/603514/)
    >> - [PATCH v9 00/19] VFIO support for platform and AMBA devices on ARM
    >> (http://www.spinics.net/lists/kvm-arm/msg11745.html)
    >> - [PATCH v2 0/6] vfio: type1: support for ARM SMMUS with
    >> VFIO_IOMMU_TYPE1
    >> (http://www.spinics.net/lists/kvm-arm/msg11738.html)
    >>
    >> Integrated pieces can be found at
    >> ssh://git.linaro.org/people/eric.auger/linux.git
    >> on branch irqfd_integ_v8
    >>
    >> This was was tested on Calxeda Midway, assigning the xgmac main IRQ.
    >>
    >
    > Hi Eric,
    >
    > Did you send out the latest QEMU part for this patch set, I notice that v6 of
    > The QEMU part is sent out, but seems some structure in this new version
    > has been changed, such as, struct kvm_arch_forwarded_irq (subindex is added
    > in this version), so a new patchset in QEMU is also needed.

    Hi Feng,

    v7 is available at:
    http://lists.gnu.org/archive/html/qemu-devel/2014-10/msg03804.html. It
    already illustrates KVM-VFIO device usage.

    v8 which will indeed integrate subindex addition will be delivered this
    week.

    Best Regards

    Eric
    >
    > Thanks,
    > Feng
    >
    >
    >> v2 -> v3:
    >> - kvm_fwd_irq_action enum replaced by a bool (KVM_VFIO_IRQ_CLEANUP does
    >> not
    >> exist anymore)
    >> - a new struct local to vfio.c was introduced to wrap kvm_fw_irq and make it
    >> linkable: kvm_vfio_fwd_irq_node
    >> - kvm_fwd_irq now is self-contained (includes struct vfio_device *)
    >> - a single list of kvm_vfio_fwd_irq_irq_node is used instead of having
    >> a list of devices and a list of forward irq per device. Having 2 lists
    >> brought extra complexity.
    >> - the VFIO device ref counter is incremented each time a new IRQ is forwarded.
    >> It is not attempted anymore to hold a single reference whatever the number
    >> of forwarded IRQs.
    >> - subindex added on top of index to be closer to VFIO API
    >> - platform device check moved in the arm specific implementation
    >> - enable the KVM-VFIO device for arm64
    >> - forwarded state change only can happen while the VFIO IRQ handler is not
    >> set; in other words, when the VFIO IRQ signaling is not set.
    >>
    >> 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 (7):
    >> KVM: arm64: Enable the KVM-VFIO device
    >> VFIO: platform: forwarded state tested when selecting IRQ handler
    >> KVM: kvm-vfio: User API for IRQ forwarding
    >> VFIO: External user API device helpers
    >> KVM: kvm-vfio: wrapper to VFIO external API device helpers
    >> KVM: kvm-vfio: generic forwarding control
    >> KVM: arm: kvm-vfio: forwarding control
    >>
    >> Kim Phillips (1):
    >> KVM: arm: Enable the KVM-VFIO device
    >>
    >> Documentation/virtual/kvm/devices/vfio.txt | 34 +++-
    >> 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 | 101 ++++++++++
    >> arch/arm64/kvm/Kconfig | 1 +
    >> arch/arm64/kvm/Makefile | 2 +-
    >> drivers/vfio/platform/vfio_platform_irq.c | 7 +-
    >> drivers/vfio/vfio.c | 24 +++
    >> include/linux/kvm_host.h | 28 +++
    >> include/linux/vfio.h | 3 +
    >> include/uapi/linux/kvm.h | 10 +
    >> virt/kvm/vfio.c | 294
    >> ++++++++++++++++++++++++++++-
    >> 13 files changed, 503 insertions(+), 13 deletions(-)
    >> create mode 100644 arch/arm/kvm/kvm_vfio_arm.c
    >>
    >> --
    >> 1.9.1
    >



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