Trait VhostUserBackendMut

pub trait VhostUserBackendMut: Send + Sync {
    type Bitmap: Bitmap + 'static;
    type Vring: VringT<GuestMemoryAtomic<GuestMemoryMmap<Self::Bitmap>>>;

    // Required methods
    fn num_queues(&self) -> usize;
    fn max_queue_size(&self) -> usize;
    fn features(&self) -> u64;
    fn protocol_features(&self) -> VhostUserProtocolFeatures;
    fn set_event_idx(&mut self, enabled: bool);
    fn update_memory(
        &mut self,
        mem: GuestMemoryAtomic<GuestMemoryMmap<Self::Bitmap>>,
    ) -> Result<()>;
    fn handle_event(
        &mut self,
        device_event: u16,
        evset: EventSet,
        vrings: &[Self::Vring],
        thread_id: usize,
    ) -> Result<()>;

    // Provided methods
    fn acked_features(&mut self, _features: u64) { ... }
    fn reset_device(&mut self) { ... }
    fn get_config(&self, _offset: u32, _size: u32) -> Vec<u8>  { ... }
    fn set_config(&mut self, _offset: u32, _buf: &[u8]) -> Result<()> { ... }
    fn set_backend_req_fd(&mut self, _backend: Backend) { ... }
    fn get_shared_object(&mut self, _uuid: VhostUserSharedMsg) -> Result<File> { ... }
    fn set_gpu_socket(&mut self, _gpu_backend: GpuBackend) -> Result<()> { ... }
    fn queues_per_thread(&self) -> Vec<u64> { ... }
    fn exit_event(&self, _thread_index: usize) -> Option<EventFd> { ... }
    fn set_device_state_fd(
        &mut self,
        _direction: VhostTransferStateDirection,
        _phase: VhostTransferStatePhase,
        _file: File,
    ) -> Result<Option<File>> { ... }
    fn check_device_state(&self) -> Result<()> { ... }
}

Trait without interior mutability for vhost user backend servers to implement concrete services.

Required Associated Types

type Bitmap: Bitmap + 'static

type Vring: VringT<GuestMemoryAtomic<GuestMemoryMmap<Self::Bitmap>>>

Required Methods

fn num_queues(&self) -> usize

Get number of queues supported.

fn max_queue_size(&self) -> usize

Get maximum queue size supported.

fn features(&self) -> u64

Get available virtio features.

fn protocol_features(&self) -> VhostUserProtocolFeatures

Get available vhost protocol features.

fn set_event_idx(&mut self, enabled: bool)

Enable or disable the virtio EVENT_IDX feature

fn update_memory( &mut self, mem: GuestMemoryAtomic<GuestMemoryMmap<Self::Bitmap>>, ) -> Result<()>

Update guest memory regions.

fn handle_event( &mut self, device_event: u16, evset: EventSet, vrings: &[Self::Vring], thread_id: usize, ) -> Result<()>

Handle IO events for backend registered file descriptors.

This function gets called if the backend registered some additional listeners onto specific file descriptors. The library can handle virtqueues on its own, but does not know what to do with events happening on custom listeners.

Provided Methods

fn acked_features(&mut self, _features: u64)

Set acknowledged virtio features.

fn reset_device(&mut self)

Reset the emulated device state.

A default implementation is provided as we cannot expect all backends to implement this function.

fn get_config(&self, _offset: u32, _size: u32) -> Vec<u8>

Get virtio device configuration.

A default implementation is provided as we cannot expect all backends to implement this function.

fn set_config(&mut self, _offset: u32, _buf: &[u8]) -> Result<()>

Set virtio device configuration.

A default implementation is provided as we cannot expect all backends to implement this function.

fn set_backend_req_fd(&mut self, _backend: Backend)

Set handler for communicating with the frontend by the backend communication channel.

A default implementation is provided as we cannot expect all backends to implement this function.

fn get_shared_object(&mut self, _uuid: VhostUserSharedMsg) -> Result<File>

This method retrieves a file descriptor for a shared object, identified by a unique UUID, which can be used by the front-end for DMA. If the shared object is found, it must return a File that the frontend can use. If the shared object does not exist the function returns None (indicating no file descriptor is available).

This function returns a Result, returning an error if the backend does not implement this function.

fn set_gpu_socket(&mut self, _gpu_backend: GpuBackend) -> Result<()>

Set handler for communicating with the frontend by the gpu specific backend communication channel.

This function returns a Result, returning an error if the backend does not implement this function.

fn queues_per_thread(&self) -> Vec<u64>

Get the map to map queue index to worker thread index.

A return value of [2, 2, 4] means: the first two queues will be handled by worker thread 0, the following two queues will be handled by worker thread 1, and the last four queues will be handled by worker thread 2.

fn exit_event(&self, _thread_index: usize) -> Option<EventFd>

Provide an optional exit EventFd for the specified worker thread.

If an (EventFd, token) pair is returned, the returned EventFd will be monitored for IO events by using epoll with the specified token. When the returned EventFd is written to, the worker thread will exit.

fn set_device_state_fd( &mut self, _direction: VhostTransferStateDirection, _phase: VhostTransferStatePhase, _file: File, ) -> Result<Option<File>>

Initiate transfer of internal state for the purpose of migration to/from the back-end.

Depending on direction, the state should either be saved (i.e. serialized and written to file) or loaded (i.e. read from file and deserialized). Note that this function must not block during transfer, i.e. I/O to/from file must be done outside of this function.

fn check_device_state(&self) -> Result<()>

After transferring internal state, check for any resulting errors, including potential deserialization errors when loading state.

Although this function return a Result, the front-end will not receive any details about this error.

Implementors