[PATCH v9 0/5] irqfd support for arm/arm64

[Eric Auger]

This patch series enables irqfd on arm and arm64.

Irqfd framework enables to inject a virtual IRQ into a guest upon an
eventfd trigger. User-side uses KVM_IRQFD VM ioctl to provide KVM with
a kvm_irqfd struct that associates a VM, an eventfd, a virtual IRQ number
(aka. the gsi). When an actor signals the eventfd (typically a VFIO
platform driver), the kvm irqfd subsystem injects the gsi into the VM.

Resamplefd also is supported for level sensitive interrupts, ie. the
user can provide another eventfd that is triggered when the completion
of the virtual IRQ (gsi) is detected by the GIC.

The gsi must correspond to a shared peripheral interrupt (SPI), ie the
GIC interrupt ID is gsi + 32.

The rationale behind not supporting PPI irqfd injection is that
any device using a PPI would be a private-to-the-CPU device (timer for
instance), so its state would have to be context-switched along with the
VCPU and would require in-kernel wiring anyhow. It is not a relevant use
case for irqfds.

This patch enables CONFIG_HAVE_KVM_EVENTFD and CONFIG_HAVE_KVM_IRQFD.

No IRQ routing table is used, enabling to remove CONFIG_HAVE_KVM_IRQCHIP

The ARM virtual interrupt controller, the VGIC, is dynamically
instantiated. The user-space may attempt to assign an irqfd before
the virtual interrupt controller is ready. For that reason a
check is added in the generic irqfd code to test whether the virtual
interrupt controller is ready.

This work was tested with Calxeda Midway xgmac main interrupt with
qemu-system-arm and QEMU VFIO platform device. Also irqfd was proven
functional on several vhost-net prototypes.

Available on ssh://git.linaro.org/people/eric.auger/linux.git
branch irqfd_v9_stdalone_official_release

v8 -> v9:
- add Christoffer's Reviewed-by on "KVM: arm/arm64: add irqfd support"
  and Acked-by on "KVM: arm/arm64: remove coarse grain dist locking at
  kvm_vgic_sync_hwstate"
- replace kvm_debug by trace_kvm_set_irq and add
  BUG_ON(!vgic_initialized(kvm)) in vgic.c kvm_set_irq.

v7 -> v8:
- Address Andre's comments:
  - introduce a separate patch file for coarse grain dist lock removal at
    kvm_vgic_sync_hwstate level
  - update comment above __kvm_vgic_sync_hwstate
  - remove kvm_irq_has_notifier call
  - remove gic_initialized() check in kvm_set_irq
  - fix a typo in one comment (kvm_host.h)

v6 -> v7:
- kvm_arch_intc_initialized call introduced in first patch file
  related to kvm_arch_intc_initialized (generic part)
- add Christoffer's acks

v5 -> v6:
- take into account Christoffer's comments:
  - rename macro and function enabling to check the state of virtual
    interrupt controller (kvm_arch_intc_initialized)
  - kvm_arch_intc_initialized is declared in kvm_host.h whatever the
    archi support.
  - squash v5 patch files 3 & 4
  - KVM_CAP_IRQFD support depends on vgic_present
  - add Christoffer's Reviewed-by on last patch file

v4 -> v5:
- add the capability to check whether vgic is initialized when
  assigning an irqfd.  objective is to avoid injecting IRQ before
  this vgic is ready: this corresponds to new patch files 2, 3, 4.
- do not specifically handle early virtual IRQ injections in
  kvm_set_irq.  In case of injection when vgic is not yet ready,
  simply return an error.  User-space now has means to force vgic
  init and get notified if irqfd assign takes place too early.
- squash [PATCH v4 2/3] KVM: arm: add irqfd support and
         [PATCH v4 3/3] KVM: arm64: add irqfd support
- add Acked-by's in KVM: arm/arm64: unset CONFIG_HAVE_KVM_IRQCHIP
- some comment rewording in vgic

v3 -> v4:
- rebase on 3.18rc5
- vgic dynamic instantiation brought new challenges:
  handling of irqfd injection when vgic is not ready
- unset of CONFIG_HAVE_KVM_IRQCHIP in a separate patch
- add arm64 enable
- vgic.c style modifications according to Christoffer comments

v2 -> v3:
- removal of irq.h from eventfd.c put in a separate patch to increase
  visibility
- properly expose KVM_CAP_IRQFD capability in arm.c
- remove CONFIG_HAVE_KVM_IRQCHIP meaningfull only if irq_comm.c is used

v1 -> v2:
- rebase on 3.17rc1
- move of the dist unlock in process_maintenance
- remove of dist lock in __kvm_vgic_sync_hwstate
- rewording of the commit message (add resamplefd reference)
- remove irq.h

Eric Auger (5):
  KVM: arm/arm64: unset CONFIG_HAVE_KVM_IRQCHIP
  KVM: introduce kvm_arch_intc_initialized and use it in irqfd
  KVM: arm/arm64: implement kvm_arch_intc_initialized
  KVM: arm/arm64: remove coarse grain dist locking at
    kvm_vgic_sync_hwstate
  KVM: arm/arm64: add irqfd support

 Documentation/virtual/kvm/api.txt |  6 +++-
 arch/arm/include/asm/kvm_host.h   |  2 ++
 arch/arm/include/uapi/asm/kvm.h   |  3 ++
 arch/arm/kvm/Kconfig              |  4 +--
 arch/arm/kvm/Makefile             |  2 +-
 arch/arm/kvm/arm.c                | 10 +++++++
 arch/arm64/include/asm/kvm_host.h |  2 ++
 arch/arm64/include/uapi/asm/kvm.h |  3 ++
 arch/arm64/kvm/Kconfig            |  3 +-
 arch/arm64/kvm/Makefile           |  2 +-
 include/linux/kvm_host.h          | 14 +++++++++
 virt/kvm/arm/vgic.c               | 61 ++++++++++++++++++++++++++++++++++-----
 virt/kvm/eventfd.c                |  3 ++
 13 files changed, 101 insertions(+), 14 deletions(-)

-- 
1.9.1