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+FLIC (floating interrupt controller)
+====================================
+
+FLIC handles floating (non per-cpu) interrupts, i.e. I/O, service and some
+machine check interruptions. All interrupts are stored in a per-vm list of
+pending interrupts. FLIC performs operations on this list.
+
+Only one FLIC instance may be instantiated.
+
+FLIC provides support to
+- add interrupts (KVM_DEV_FLIC_ENQUEUE)
+- inspect currently pending interrupts (KVM_FLIC_GET_ALL_IRQS)
+- purge all pending floating interrupts (KVM_DEV_FLIC_CLEAR_IRQS)
+- purge one pending floating I/O interrupt (KVM_DEV_FLIC_CLEAR_IO_IRQ)
+- enable/disable for the guest transparent async page faults
+- register and modify adapter interrupt sources (KVM_DEV_FLIC_ADAPTER_*)
+- modify AIS (adapter-interruption-suppression) mode state (KVM_DEV_FLIC_AISM)
+- inject adapter interrupts on a specified adapter (KVM_DEV_FLIC_AIRQ_INJECT)
+- get/set all AIS mode states (KVM_DEV_FLIC_AISM_ALL)
+
+Groups:
+  KVM_DEV_FLIC_ENQUEUE
+    Passes a buffer and length into the kernel which are then injected into
+    the list of pending interrupts.
+    attr->addr contains the pointer to the buffer and attr->attr contains
+    the length of the buffer.
+    The format of the data structure kvm_s390_irq as it is copied from userspace
+    is defined in usr/include/linux/kvm.h.
+
+  KVM_DEV_FLIC_GET_ALL_IRQS
+    Copies all floating interrupts into a buffer provided by userspace.
+    When the buffer is too small it returns -ENOMEM, which is the indication
+    for userspace to try again with a bigger buffer.
+    -ENOBUFS is returned when the allocation of a kernelspace buffer has
+    failed.
+    -EFAULT is returned when copying data to userspace failed.
+    All interrupts remain pending, i.e. are not deleted from the list of
+    currently pending interrupts.
+    attr->addr contains the userspace address of the buffer into which all
+    interrupt data will be copied.
+    attr->attr contains the size of the buffer in bytes.
+
+  KVM_DEV_FLIC_CLEAR_IRQS
+    Simply deletes all elements from the list of currently pending floating
+    interrupts.  No interrupts are injected into the guest.
+
+  KVM_DEV_FLIC_CLEAR_IO_IRQ
+    Deletes one (if any) I/O interrupt for a subchannel identified by the
+    subsystem identification word passed via the buffer specified by
+    attr->addr (address) and attr->attr (length).
+
+  KVM_DEV_FLIC_APF_ENABLE
+    Enables async page faults for the guest. So in case of a major page fault
+    the host is allowed to handle this async and continues the guest.
+
+  KVM_DEV_FLIC_APF_DISABLE_WAIT
+    Disables async page faults for the guest and waits until already pending
+    async page faults are done. This is necessary to trigger a completion interrupt
+    for every init interrupt before migrating the interrupt list.
+
+  KVM_DEV_FLIC_ADAPTER_REGISTER
+    Register an I/O adapter interrupt source. Takes a kvm_s390_io_adapter
+    describing the adapter to register:
+
+struct kvm_s390_io_adapter {
+	__u32 id;
+	__u8 isc;
+	__u8 maskable;
+	__u8 swap;
+	__u8 flags;
+};
+
+   id contains the unique id for the adapter, isc the I/O interruption subclass
+   to use, maskable whether this adapter may be masked (interrupts turned off),
+   swap whether the indicators need to be byte swapped, and flags contains
+   further characteristics of the adapter.
+   Currently defined values for 'flags' are:
+   - KVM_S390_ADAPTER_SUPPRESSIBLE: adapter is subject to AIS
+     (adapter-interrupt-suppression) facility. This flag only has an effect if
+     the AIS capability is enabled.
+   Unknown flag values are ignored.
+
+
+  KVM_DEV_FLIC_ADAPTER_MODIFY
+    Modifies attributes of an existing I/O adapter interrupt source. Takes
+    a kvm_s390_io_adapter_req specifying the adapter and the operation:
+
+struct kvm_s390_io_adapter_req {
+	__u32 id;
+	__u8 type;
+	__u8 mask;
+	__u16 pad0;
+	__u64 addr;
+};
+
+    id specifies the adapter and type the operation. The supported operations
+    are:
+
+    KVM_S390_IO_ADAPTER_MASK
+      mask or unmask the adapter, as specified in mask
+
+    KVM_S390_IO_ADAPTER_MAP
+      perform a gmap translation for the guest address provided in addr,
+      pin a userspace page for the translated address and add it to the
+      list of mappings
+      Note: A new mapping will be created unconditionally; therefore,
+            the calling code should avoid making duplicate mappings.
+
+    KVM_S390_IO_ADAPTER_UNMAP
+      release a userspace page for the translated address specified in addr
+      from the list of mappings
+
+  KVM_DEV_FLIC_AISM
+    modify the adapter-interruption-suppression mode for a given isc if the
+    AIS capability is enabled. Takes a kvm_s390_ais_req describing:
+
+struct kvm_s390_ais_req {
+	__u8 isc;
+	__u16 mode;
+};
+
+    isc contains the target I/O interruption subclass, mode the target
+    adapter-interruption-suppression mode. The following modes are
+    currently supported:
+    - KVM_S390_AIS_MODE_ALL: ALL-Interruptions Mode, i.e. airq injection
+      is always allowed;
+    - KVM_S390_AIS_MODE_SINGLE: SINGLE-Interruption Mode, i.e. airq
+      injection is only allowed once and the following adapter interrupts
+      will be suppressed until the mode is set again to ALL-Interruptions
+      or SINGLE-Interruption mode.
+
+  KVM_DEV_FLIC_AIRQ_INJECT
+    Inject adapter interrupts on a specified adapter.
+    attr->attr contains the unique id for the adapter, which allows for
+    adapter-specific checks and actions.
+    For adapters subject to AIS, handle the airq injection suppression for
+    an isc according to the adapter-interruption-suppression mode on condition
+    that the AIS capability is enabled.
+
+  KVM_DEV_FLIC_AISM_ALL
+    Gets or sets the adapter-interruption-suppression mode for all ISCs. Takes
+    a kvm_s390_ais_all describing:
+
+struct kvm_s390_ais_all {
+       __u8 simm; /* Single-Interruption-Mode mask */
+       __u8 nimm; /* No-Interruption-Mode mask *
+};
+
+    simm contains Single-Interruption-Mode mask for all ISCs, nimm contains
+    No-Interruption-Mode mask for all ISCs. Each bit in simm and nimm corresponds
+    to an ISC (MSB0 bit 0 to ISC 0 and so on). The combination of simm bit and
+    nimm bit presents AIS mode for a ISC.
+
+    KVM_DEV_FLIC_AISM_ALL is indicated by KVM_CAP_S390_AIS_MIGRATION.
+
+Note: The KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR device ioctls executed on
+FLIC with an unknown group or attribute gives the error code EINVAL (instead of
+ENXIO, as specified in the API documentation). It is not possible to conclude
+that a FLIC operation is unavailable based on the error code resulting from a
+usage attempt.
+
+Note: The KVM_DEV_FLIC_CLEAR_IO_IRQ ioctl will return EINVAL in case a zero
+schid is specified.