VFIO virtual device

Device types supported:

• KVM_DEV_TYPE_VFIO

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.