Documentation/virt/kvm/devices/vfio.rst
.. SPDX-License-Identifier: GPL-2.0
Device types supported:
Only one VFIO instance may be created per VM. The created device tracks VFIO files (group or device) in use by the VM and features of those groups/devices important to the correctness and acceleration of the VM. As groups/devices are enabled and disabled for use by the VM, KVM should be updated about their presence. When registered with KVM, a reference to the VFIO file is held by KVM.
Groups: KVM_DEV_VFIO_FILE alias: KVM_DEV_VFIO_GROUP
KVM_DEV_VFIO_FILE attributes: KVM_DEV_VFIO_FILE_ADD: Add a VFIO file (group/device) to VFIO-KVM device tracking
kvm_device_attr.addr points to an int32_t file descriptor for the
VFIO file.
KVM_DEV_VFIO_FILE_DEL: Remove a VFIO file (group/device) from VFIO-KVM device tracking
kvm_device_attr.addr points to an int32_t file descriptor for the
VFIO file.
KVM_DEV_VFIO_GROUP (legacy kvm device group restricted to the handling of VFIO group fd): KVM_DEV_VFIO_GROUP_ADD: same as KVM_DEV_VFIO_FILE_ADD for group fd only
KVM_DEV_VFIO_GROUP_DEL: same as KVM_DEV_VFIO_FILE_DEL for group fd only
KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table allocated by sPAPR KVM. kvm_device_attr.addr points to a struct::
struct kvm_vfio_spapr_tce {
__s32 groupfd;
__s32 tablefd;
};
where:
- @groupfd is a file descriptor for a VFIO group;
- @tablefd is a file descriptor for a TCE table allocated via
KVM_CREATE_SPAPR_TCE.
The FILE/GROUP_ADD operation above should be invoked prior to accessing the device file descriptor via VFIO_GROUP_GET_DEVICE_FD in order to support drivers which require a kvm pointer to be set in their .open_device() callback. It is the same for device file descriptor via character device open which gets device access via VFIO_DEVICE_BIND_IOMMUFD. For such file descriptors, FILE_ADD should be invoked before VFIO_DEVICE_BIND_IOMMUFD to support the drivers mentioned in prior sentence as well.