[PATCH v3 0/8] KVM-VFIO IRQ forward control

Wu, Feng
2014-11-24T08:34:43Z

> -----Original Message-----
> From: Eric Auger [mailto:eric.auger at linaro.org]
> Sent: Monday, November 24, 2014 4:27 PM
> To: Wu, Feng; eric.auger at st.com; christoffer.dall at linaro.org;
> marc.zyngier at arm.com; linux-arm-kernel at lists.infradead.org;
> kvmarm at lists.cs.columbia.edu; kvm at vger.kernel.org;
> alex.williamson at redhat.com; joel.schopp at amd.com;
> kim.phillips at freescale.com; paulus at samba.org; gleb at kernel.org;
> pbonzini at redhat.com; agraf at suse.de
> Cc: linux-kernel at vger.kernel.org; patches at linaro.org; will.deacon at arm.com;
> a.motakis at virtualopensystems.com; a.rigo at virtualopensystems.com;
> john.liuli at huawei.com; ming.lei at canonical.com
> Subject: Re: [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 at linaro.org]
> >> Sent: Monday, November 24, 2014 2:36 AM
> >> To: eric.auger at st.com; eric.auger at linaro.org; christoffer.dall at linaro.org;
> >> marc.zyngier at arm.com; linux-arm-kernel at lists.infradead.org;
> >> kvmarm at lists.cs.columbia.edu; kvm at vger.kernel.org;
> >> alex.williamson at redhat.com; joel.schopp at amd.com;
> >> kim.phillips at freescale.com; paulus at samba.org; gleb at kernel.org;
> >> pbonzini at redhat.com; agraf at suse.de
> >> Cc: linux-kernel at vger.kernel.org; patches at linaro.org;
> will.deacon at arm.com;
> >> a.motakis at virtualopensystems.com; a.rigo at virtualopensystems.com;
> >> john.liuli at huawei.com; ming.lei at 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 a lot for the information, Eric!

Thanks,
Feng

> >
> > 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
> >