Struct VirtQueue 

pub struct VirtQueue { /* private fields */ }

A split virtqueue managing descriptors, available ring, and used ring.

Owns the physical memory backing all three structures. The physical page frame number (PFN) is communicated to the device so it can DMA directly.

Implementations

impl VirtQueue

pub fn new(size: u16) -> Result<Self, KernelError>

Allocate and initialize a new virtqueue.

Allocates physically contiguous memory for the descriptor table, available ring, and used ring. The memory is zeroed and the free descriptor list is linked.

size is typically read from the device via QUEUE_SIZE register and should be a power of 2. If size is 0 or exceeds our compiled maximum, we clamp to DEFAULT_QUEUE_SIZE.

pub fn pfn(&self) -> u32

Get the physical page frame number for the QUEUE_ADDRESS register.

pub fn phys_desc(&self) -> u64

Physical addresses for mmio transports (virtio-mmio expects 64-bit phys)

pub fn phys_avail(&self) -> u64

pub fn phys_used(&self) -> u64

pub fn size(&self) -> u16

Get the queue size.

pub fn alloc_desc(&mut self) -> Option<u16>

Allocate a single free descriptor, returning its index.

Returns None if all descriptors are in use.

pub fn free_desc(&mut self, idx: u16)

Return a descriptor to the free list.

pub fn free_chain(&mut self, head: u16)

Free a chain of descriptors linked via NEXT flags, starting at head.

pub unsafe fn write_desc( &mut self, idx: u16, phys_addr: u64, len: u32, flags: u16, next: u16, )

Write a descriptor’s fields.

Safety

idx must be a valid descriptor index (< queue size). phys_addr must point to a valid guest physical buffer of at least len bytes that will remain valid until the device returns the descriptor via the used ring.

pub fn push_avail(&mut self, desc_head: u16)

Push a descriptor chain head onto the available ring and advance the available index.

The caller must call kick() (via the transport) after one or more push_avail() calls to notify the device.

pub fn poll_used(&mut self) -> Option<(u16, u32)>

Poll the used ring for a completed buffer.

Returns Some((chain_head_index, bytes_written)) if the device has returned a buffer, or None if no new completions are available.

The caller should free the returned descriptor chain via free_chain().

pub fn has_used(&self) -> bool

Check if any completions are pending without consuming them.

Trait Implementations

impl Drop for VirtQueue

fn drop(&mut self)

Executes the destructor for this type.

impl Send for VirtQueue

impl Sync for VirtQueue