1.. SPDX-License-Identifier: GPL-2.0
2
3===================
4VFIO virtual device
5===================
6
7Device types supported:
8
9  - KVM_DEV_TYPE_VFIO
10
11Only one VFIO instance may be created per VM.  The created device
12tracks VFIO files (group or device) in use by the VM and features
13of those groups/devices important to the correctness and acceleration
14of the VM.  As groups/devices are enabled and disabled for use by the
15VM, KVM should be updated about their presence.  When registered with
16KVM, a reference to the VFIO file is held by KVM.
17
18Groups:
19  KVM_DEV_VFIO_FILE
20	alias: KVM_DEV_VFIO_GROUP
21
22KVM_DEV_VFIO_FILE attributes:
23  KVM_DEV_VFIO_FILE_ADD: Add a VFIO file (group/device) to VFIO-KVM device
24	tracking
25
26	kvm_device_attr.addr points to an int32_t file descriptor for the
27	VFIO file.
28
29  KVM_DEV_VFIO_FILE_DEL: Remove a VFIO file (group/device) from VFIO-KVM
30	device tracking
31
32	kvm_device_attr.addr points to an int32_t file descriptor for the
33	VFIO file.
34
35KVM_DEV_VFIO_GROUP (legacy kvm device group restricted to the handling of VFIO group fd):
36  KVM_DEV_VFIO_GROUP_ADD: same as KVM_DEV_VFIO_FILE_ADD for group fd only
37
38  KVM_DEV_VFIO_GROUP_DEL: same as KVM_DEV_VFIO_FILE_DEL for group fd only
39
40  KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
41	allocated by sPAPR KVM.
42	kvm_device_attr.addr points to a struct::
43
44		struct kvm_vfio_spapr_tce {
45			__s32	groupfd;
46			__s32	tablefd;
47		};
48
49	where:
50
51	- @groupfd is a file descriptor for a VFIO group;
52	- @tablefd is a file descriptor for a TCE table allocated via
53	  KVM_CREATE_SPAPR_TCE.
54
55The FILE/GROUP_ADD operation above should be invoked prior to accessing the
56device file descriptor via VFIO_GROUP_GET_DEVICE_FD in order to support
57drivers which require a kvm pointer to be set in their .open_device()
58callback.  It is the same for device file descriptor via character device
59open which gets device access via VFIO_DEVICE_BIND_IOMMUFD.  For such file
60descriptors, FILE_ADD should be invoked before VFIO_DEVICE_BIND_IOMMUFD
61to support the drivers mentioned in prior sentence as well.
62