Struct UsedRing 

pub struct UsedRing<T: GuestMemoryAccessor + Clone> {
    pub base_addr: GuestPhysAddr,
    pub size: u16,
    pub used_idx: u16,
    /* private fields */
}

Used ring management structure.

This structure provides a high-level interface for managing the VirtIO used ring in guest memory. It wraps the guest memory accessor and provides methods to read/write various parts of the used ring:

• The header (VirtQueueUsed structure)
• The ring array of used elements (VirtqUsedElem structures)
• The avail_event field (if VIRTIO_F_EVENT_IDX is negotiated)

Relationship with VirtQueueUsed and VirtqUsedElem:

• VirtQueueUsed defines the memory layout of the used ring header
• VirtqUsedElem defines the memory layout of each ring element
• UsedRing uses both structures to access the complete used ring in guest memory
• UsedRing manages the entire used ring structure and provides high-level operations

Memory Layout:

base_addr -> +-------------------+
             | VirtQueueUsed     |  (flags + idx)
             +-------------------+
             | ring[0]           |  (VirtqUsedElem: id + len)
             | ring[1]           |  (VirtqUsedElem: id + len)
             | ...               |
             | ring[queue_size-1]|  (VirtqUsedElem: id + len)
             +-------------------+
             | avail_event       |  (optional, if event_idx enabled)
             +-------------------+

Fields

base_addr: GuestPhysAddr

Base address of the used ring

size: u16

Queue size

used_idx: u16

Current used index

Implementations

impl<T: GuestMemoryAccessor + Clone> UsedRing<T>

pub fn new(base_addr: GuestPhysAddr, size: u16, accessor: Arc<T>) -> Self

Create a new used ring

pub fn header_addr(&self) -> GuestPhysAddr

Get the address of the used ring header

pub fn ring_addr(&self) -> GuestPhysAddr

Get the address of the ring array

pub fn ring_entry_addr(&self, index: u16) -> Option<GuestPhysAddr>

Get the address of a specific ring entry

pub fn avail_event_addr(&self) -> GuestPhysAddr

Get the address of the available event field (if event_idx is enabled)

pub fn total_size(&self) -> usize

Calculate the total size of the used ring

pub fn is_valid(&self) -> bool

Check if the used ring is valid

pub fn add_used(&mut self, id: u32, len: u32) -> VirtioResult<()>

Add a used element to the ring

pub fn write_used_idx(&self) -> VirtioResult<()>

Write the used index to the used ring header

pub fn read_used_header(&self) -> VirtioResult<VirtQueueUsed>

Read the used ring header

pub fn write_used_header(&self, header: &VirtQueueUsed) -> VirtioResult<()>

Write the used ring header

pub fn get_used_idx(&self) -> u16

Get the current used index

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

Set the used index

pub fn should_notify(&self) -> VirtioResult<bool>

Check if notifications should be suppressed

pub fn set_notification(&self, suppress: bool) -> VirtioResult<()>

Set notification suppression

Trait Implementations

impl<T: Clone + GuestMemoryAccessor + Clone> Clone for UsedRing<T>

fn clone(&self) -> UsedRing<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Debug + GuestMemoryAccessor + Clone> Debug for UsedRing<T>

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

Formats the value using the given formatter.