Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / Documentation / virtual / kvm / devices / s390_flic.txt

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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)
+- enable/disable for the guest transparent async page faults
+- register and modify adapter interrupt sources (KVM_DEV_FLIC_ADAPTER_*)
+
+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_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 pad;
+};
+
+   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)
+   and swap whether the indicators need to be byte swapped.
+
+
+  KVM_DEV_FLIC_ADAPTER_MODIFY
+    Modifies attributes of an existing I/O adapter interrupt source. Takes
+    a kvm_s390_io_adapter_req specifiying 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
+
+    KVM_S390_IO_ADAPTER_UNMAP
+      release a userspace page for the translated address specified in addr
+      from the list of mappings