Struct Queue 

pub struct Queue {
    pub max_size: u16,
    pub size: u16,
    pub ready: bool,
    pub desc_table_addr: GuestAddress,
    pub avail_ring_addr: GuestAddress,
    pub used_ring_addr: GuestAddress,
    pub next_avail_idx: u16,
    pub next_used_idx: u16,
}

Per-queue setup state and runtime cursor.

The transport mutates size, *_addr, and ready in response to guest MMIO writes during driver init. The device handler mutates next_avail_idx as it consumes descriptor heads.

Fields

max_size: u16

Maximum descriptor count negotiated at boot (the device exposes this as QueueNumMax).

size: u16

Active descriptor count. Bounded by max_size. Set by the driver writing QueueNum.

ready: bool

true once the driver writes QueueReady = 1.

desc_table_addr: GuestAddress

Guest-physical address of the descriptor table.

avail_ring_addr: GuestAddress

Guest-physical address of the available ring.

used_ring_addr: GuestAddress

Guest-physical address of the used ring.

next_avail_idx: u16

Device-side cursor into the available ring.

next_used_idx: u16

Device-side cursor into the used ring (the next slot to write to).

Implementations

impl Queue

pub fn new(max_size: u16) -> Self

Build a fresh queue with the given maximum descriptor count.

pub fn set_size(&mut self, requested: u16)

Set the negotiated descriptor count, clamping to max_size and to a power of two as the spec requires.

pub fn is_valid(&self) -> bool

true when every required address is set and ready = 1.

pub fn reset(&mut self)

Reset the queue cursors and clear the ready flag. Called when the driver writes Status = INIT.

pub fn pop_avail<M: GuestMemory + ?Sized>( &mut self, mem: &M, ) -> Result<Option<DescriptorChain>, QueueError>

Pop the next descriptor head from the available ring.

Returns Ok(None) if the driver has not made any new descriptors available since the last call.

Errors

QueueError for any underlying memory access failure.

pub fn push_used<M: GuestMemory + ?Sized>( &mut self, mem: &M, head_index: u16, bytes_written: u32, ) -> Result<(), QueueError>

Push a completed descriptor chain into the used ring.

head_index is the descriptor index returned by pop_avail; bytes_written is the total bytes the device wrote into device-write descriptors of the chain (zero for purely device-read chains).

Errors

QueueError for any underlying memory access failure.

Trait Implementations

impl Clone for Queue

fn clone(&self) -> Queue

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Queue

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.