tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1.. SPDX-License-Identifier: GPL-2.0
2
3====================================
4FLIC (floating interrupt controller)
5====================================
6
7FLIC handles floating (non per-cpu) interrupts, i.e. I/O, service and some
8machine check interruptions. All interrupts are stored in a per-vm list of
9pending interrupts. FLIC performs operations on this list.
10
11Only one FLIC instance may be instantiated.
12
13FLIC provides support to
14- add interrupts (KVM_DEV_FLIC_ENQUEUE)
15- inspect currently pending interrupts (KVM_FLIC_GET_ALL_IRQS)
16- purge all pending floating interrupts (KVM_DEV_FLIC_CLEAR_IRQS)
17- purge one pending floating I/O interrupt (KVM_DEV_FLIC_CLEAR_IO_IRQ)
18- enable/disable for the guest transparent async page faults
19- register and modify adapter interrupt sources (KVM_DEV_FLIC_ADAPTER_*)
20- modify AIS (adapter-interruption-suppression) mode state (KVM_DEV_FLIC_AISM)
21- inject adapter interrupts on a specified adapter (KVM_DEV_FLIC_AIRQ_INJECT)
22- get/set all AIS mode states (KVM_DEV_FLIC_AISM_ALL)
23
24Groups:
25 KVM_DEV_FLIC_ENQUEUE
26 Passes a buffer and length into the kernel which are then injected into
27 the list of pending interrupts.
28 attr->addr contains the pointer to the buffer and attr->attr contains
29 the length of the buffer.
30 The format of the data structure kvm_s390_irq as it is copied from userspace
31 is defined in usr/include/linux/kvm.h.
32
33 KVM_DEV_FLIC_GET_ALL_IRQS
34 Copies all floating interrupts into a buffer provided by userspace.
35 When the buffer is too small it returns -ENOMEM, which is the indication
36 for userspace to try again with a bigger buffer.
37
38 -ENOBUFS is returned when the allocation of a kernelspace buffer has
39 failed.
40
41 -EFAULT is returned when copying data to userspace failed.
42 All interrupts remain pending, i.e. are not deleted from the list of
43 currently pending interrupts.
44 attr->addr contains the userspace address of the buffer into which all
45 interrupt data will be copied.
46 attr->attr contains the size of the buffer in bytes.
47
48 KVM_DEV_FLIC_CLEAR_IRQS
49 Simply deletes all elements from the list of currently pending floating
50 interrupts. No interrupts are injected into the guest.
51
52 KVM_DEV_FLIC_CLEAR_IO_IRQ
53 Deletes one (if any) I/O interrupt for a subchannel identified by the
54 subsystem identification word passed via the buffer specified by
55 attr->addr (address) and attr->attr (length).
56
57 KVM_DEV_FLIC_APF_ENABLE
58 Enables async page faults for the guest. So in case of a major page fault
59 the host is allowed to handle this async and continues the guest.
60
61 KVM_DEV_FLIC_APF_DISABLE_WAIT
62 Disables async page faults for the guest and waits until already pending
63 async page faults are done. This is necessary to trigger a completion interrupt
64 for every init interrupt before migrating the interrupt list.
65
66 KVM_DEV_FLIC_ADAPTER_REGISTER
67 Register an I/O adapter interrupt source. Takes a kvm_s390_io_adapter
68 describing the adapter to register::
69
70 struct kvm_s390_io_adapter {
71 __u32 id;
72 __u8 isc;
73 __u8 maskable;
74 __u8 swap;
75 __u8 flags;
76 };
77
78 id contains the unique id for the adapter, isc the I/O interruption subclass
79 to use, maskable whether this adapter may be masked (interrupts turned off),
80 swap whether the indicators need to be byte swapped, and flags contains
81 further characteristics of the adapter.
82
83 Currently defined values for 'flags' are:
84
85 - KVM_S390_ADAPTER_SUPPRESSIBLE: adapter is subject to AIS
86 (adapter-interrupt-suppression) facility. This flag only has an effect if
87 the AIS capability is enabled.
88
89 Unknown flag values are ignored.
90
91
92 KVM_DEV_FLIC_ADAPTER_MODIFY
93 Modifies attributes of an existing I/O adapter interrupt source. Takes
94 a kvm_s390_io_adapter_req specifying the adapter and the operation::
95
96 struct kvm_s390_io_adapter_req {
97 __u32 id;
98 __u8 type;
99 __u8 mask;
100 __u16 pad0;
101 __u64 addr;
102 };
103
104 id specifies the adapter and type the operation. The supported operations
105 are:
106
107 KVM_S390_IO_ADAPTER_MASK
108 mask or unmask the adapter, as specified in mask
109
110 KVM_S390_IO_ADAPTER_MAP
111 This is now a no-op. The mapping is purely done by the irq route.
112 KVM_S390_IO_ADAPTER_UNMAP
113 This is now a no-op. The mapping is purely done by the irq route.
114
115 KVM_DEV_FLIC_AISM
116 modify the adapter-interruption-suppression mode for a given isc if the
117 AIS capability is enabled. Takes a kvm_s390_ais_req describing::
118
119 struct kvm_s390_ais_req {
120 __u8 isc;
121 __u16 mode;
122 };
123
124 isc contains the target I/O interruption subclass, mode the target
125 adapter-interruption-suppression mode. The following modes are
126 currently supported:
127
128 - KVM_S390_AIS_MODE_ALL: ALL-Interruptions Mode, i.e. airq injection
129 is always allowed;
130 - KVM_S390_AIS_MODE_SINGLE: SINGLE-Interruption Mode, i.e. airq
131 injection is only allowed once and the following adapter interrupts
132 will be suppressed until the mode is set again to ALL-Interruptions
133 or SINGLE-Interruption mode.
134
135 KVM_DEV_FLIC_AIRQ_INJECT
136 Inject adapter interrupts on a specified adapter.
137 attr->attr contains the unique id for the adapter, which allows for
138 adapter-specific checks and actions.
139 For adapters subject to AIS, handle the airq injection suppression for
140 an isc according to the adapter-interruption-suppression mode on condition
141 that the AIS capability is enabled.
142
143 KVM_DEV_FLIC_AISM_ALL
144 Gets or sets the adapter-interruption-suppression mode for all ISCs. Takes
145 a kvm_s390_ais_all describing::
146
147 struct kvm_s390_ais_all {
148 __u8 simm; /* Single-Interruption-Mode mask */
149 __u8 nimm; /* No-Interruption-Mode mask *
150 };
151
152 simm contains Single-Interruption-Mode mask for all ISCs, nimm contains
153 No-Interruption-Mode mask for all ISCs. Each bit in simm and nimm corresponds
154 to an ISC (MSB0 bit 0 to ISC 0 and so on). The combination of simm bit and
155 nimm bit presents AIS mode for a ISC.
156
157 KVM_DEV_FLIC_AISM_ALL is indicated by KVM_CAP_S390_AIS_MIGRATION.
158
159Note: The KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR device ioctls executed on
160FLIC with an unknown group or attribute gives the error code EINVAL (instead of
161ENXIO, as specified in the API documentation). It is not possible to conclude
162that a FLIC operation is unavailable based on the error code resulting from a
163usage attempt.
164
165.. note:: The KVM_DEV_FLIC_CLEAR_IO_IRQ ioctl will return EINVAL in case a
166 zero schid is specified.