Driver-side implementation of a Virtqueue. More...

#include <virtqueue>

Inheritance diagram for L4virtio::Driver::Virtqueue:

Collaboration diagram for L4virtio::Driver::Virtqueue:

Public Member Functions
void	initialize_rings (unsigned num)
	Initialize the descriptor table and the index structures of this queue.

void	init_queue (unsigned num, void desc, void avail, void *used)
	Initialize this virtqueue.

void	init_queue (unsigned num, void *base)
	Initialize this virtqueue.

l4_uint16_t	alloc_descriptor ()
	Allocate and return an unused descriptor from the descriptor table.

void	enqueue_descriptor (l4_uint16_t descno)
	Enqueue a descriptor in the available ring.

Desc &	desc (l4_uint16_t descno)
	Return a reference to a descriptor in the descriptor table.

l4_uint16_t	find_next_used (l4_uint32_t *len=nullptr)
	Return the next finished block.

void	free_descriptor (l4_uint16_t head, l4_uint16_t tail)
	Free a chained list of descriptors in the descriptor queue.

Public Member Functions inherited from L4virtio::Virtqueue
void	disable ()
	Completely disable the queue.

unsigned long	total_size () const
	Calculate the total size of this virtqueue.

unsigned long	avail_offset () const
	Get the offset of the available ring from the descriptor table.

unsigned long	used_offset () const
	Get the offset of the used ring from the descriptor table.

void	setup (unsigned num, void desc, void avail, void *used)
	Enable this queue.

void	setup_simple (unsigned num, void *ring)
	Enable this queue.

void	dump (Desc const *d) const
	Dump descriptors for this queue.

bool	ready () const
	Test if this queue is in working state.

unsigned	num () const

bool	no_notify_guest () const
	Get the no IRQ flag of this queue.

bool	no_notify_host () const
	Get the no notify flag of this queue.

void	no_notify_host (bool value)
	Set the no-notify flag for this queue.

l4_uint16_t	get_avail_idx () const
	Get available index from available ring (for debugging).

l4_uint16_t	get_tail_avail_idx () const
	Get tail-available index stored in local state (for debugging).

Additional Inherited Members
Public Types inherited from L4virtio::Virtqueue
enum
	Fixed alignment values for different parts of a virtqueue.

Static Public Member Functions inherited from L4virtio::Virtqueue
static unsigned long	total_size (unsigned num)
	Calculate the total size for a virtqueue of the given dimensions.

static unsigned long	desc_size (unsigned num)
	Calculate the size of the descriptor table for `num` entries.

static unsigned long	desc_align ()
	Get the alignment in zero LSBs needed for the descriptor table.

static unsigned long	avail_size (unsigned num)
	Calculate the size of the available ring for `num` entries.

static unsigned long	avail_align ()
	Get the alignment in zero LSBs needed for the available ring.

static unsigned long	used_size (unsigned num)
	Calculate the size of the used ring for `num` entries.

static unsigned long	used_align ()
	Get the alignment in zero LSBs needed for the used ring.

Protected Member Functions inherited from L4virtio::Virtqueue
	Virtqueue ()=default
	Create a disabled virtqueue.

Protected Attributes inherited from L4virtio::Virtqueue
Desc *	_desc = nullptr
	pointer to descriptor table, NULL if queue is off.

Avail *	_avail = nullptr
	pointer to available ring.

Used *	_used = nullptr
	pointer to used ring.

l4_uint16_t	_current_avail = 0
	The life counter for the queue.

l4_uint16_t	_idx_mask = 0
	mask used for indexing into the descriptor table and the rings.

Detailed Description

Driver-side implementation of a Virtqueue.

Adds function for managing the descriptor list, enqueueing new and dequeueing finished requests.

Note: The Virtqueue implementation is not thread-safe.

Definition at line 476 of file virtqueue.

Member Function Documentation

◆ alloc_descriptor()

l4_uint16_t L4virtio::Driver::Virtqueue::alloc_descriptor ( )

inline

Allocate and return an unused descriptor from the descriptor table.

The descriptor will be removed from the free list, the content should be considered undefined. After use, it needs to be freed using free_descriptor().

Returns: The index of the reserved descriptor or Virtqueue::Eoq if no free descriptor is available.

Note: the implementation uses (2^16 - 1) as the end of queue marker. That means that the final entry in the queue can not be allocated iff the queue size is 2^16.

Definition at line 564 of file virtqueue.

References L4virtio::Virtqueue::_desc, and L4virtio::Virtqueue::Desc::next.

Referenced by L4virtio::Driver::Block_device::add_block(), L4virtio::Driver::Block_device::process_request(), L4virtio::Driver::Virtio_net_device::queue_rx(), L4virtio::Driver::Block_device::send_request(), L4virtio::Driver::Block_device::start_request(), and L4virtio::Driver::Virtio_net_device::tx().

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◆ desc()

Desc & L4virtio::Driver::Virtqueue::desc ( l4_uint16_t descno )

inline

Return a reference to a descriptor in the descriptor table.

Parameters

descno Index of the descriptor, expected to be in correct range.

Definition at line 596 of file virtqueue.

References L4virtio::Virtqueue::_desc, and L4virtio::Virtqueue::_idx_mask.

Referenced by L4virtio::Driver::Block_device::add_block(), init_queue(), L4virtio::Driver::Block_device::process_request(), L4virtio::Driver::Block_device::send_request(), L4virtio::Driver::Virtio_net_device::setup_device(), L4virtio::Driver::Block_device::start_request(), and L4virtio::Driver::Virtio_net_device::tx().

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◆ enqueue_descriptor()

void L4virtio::Driver::Virtqueue::enqueue_descriptor ( l4_uint16_t descno )

inline

Enqueue a descriptor in the available ring.

Parameters

descno Index of the head descriptor to enqueue.

Definition at line 580 of file virtqueue.

References L4virtio::Virtqueue::_avail, L4virtio::Virtqueue::_idx_mask, L4virtio::Virtqueue::Avail::idx, and L4virtio::Virtqueue::Avail::ring.

Referenced by L4virtio::Driver::Virtio_net_device::queue_rx(), and L4virtio::Driver::Device::send().

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◆ find_next_used()

l4_uint16_t L4virtio::Driver::Virtqueue::find_next_used ( l4_uint32_t * len = nullptr )

inline

Return the next finished block.

Parameters

[out] len (optional) Size of valid data in finished block. Note that this is the value reported by the device, which may set it to a value that is larger than the original buffer size.

Returns: Index of the head or Virtqueue::Eoq if no used element is currently available.

Definition at line 615 of file virtqueue.

References L4virtio::Virtqueue::_current_avail, L4virtio::Virtqueue::_idx_mask, L4virtio::Virtqueue::_used, L4virtio::Virtqueue::Used::idx, L4virtio::Virtqueue::Used_elem::len, and L4virtio::Virtqueue::Used::ring.

Referenced by L4virtio::Driver::Block_device::process_used_queue(), and L4virtio::Driver::Device::wait_for_next_used().

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◆ free_descriptor()

void L4virtio::Driver::Virtqueue::free_descriptor	(	l4_uint16_t	head,
		l4_uint16_t	tail
	)

inline

Free a chained list of descriptors in the descriptor queue.

Parameters

head	Index of the first element in the descriptor chain.
tail	Index of the last element in the descriptor chain.

Simply takes the descriptor chain and prepends it to the beginning of the free list. Assumes that the list has been correctly chained.

Definition at line 637 of file virtqueue.

References L4virtio::Virtqueue::_desc, L4virtio::Virtqueue::_idx_mask, and L4virtio::Virtqueue::Desc::next.

Referenced by L4virtio::Driver::Virtio_net_device::finish_rx().

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◆ init_queue() [1/2]

void L4virtio::Driver::Virtqueue::init_queue	(	unsigned	num,
		void *	base
	)

inline

Initialize this virtqueue.

Parameters

num	The number of entries in the descriptor table, the available ring, and the used ring (must be a power of 2).
base	The base address for the queue data structure.

This function sets up the memory and initializes the freelist.

Definition at line 543 of file virtqueue.

References initialize_rings(), L4virtio::Virtqueue::num(), and L4virtio::Virtqueue::setup_simple().

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◆ init_queue() [2/2]

void L4virtio::Driver::Virtqueue::init_queue	(	unsigned	num,
		void *	desc,
		void *	avail,
		void *	used
	)

inline

Initialize this virtqueue.

Parameters

num	The number of entries in the descriptor table, the available ring, and the used ring (must be a power of 2).
desc	The address of the descriptor table. (Must be Desc_align aligned and at least `desc_size(num)` bytes in size.)
avail	The address of the available ring. (Must be Avail_align aligned and at least `avail_size(num)` bytes in size.)
used	The address of the used ring. (Must be Used_align aligned and at least `used_size(num)` bytes in size.)

This function sets up the memory and initializes the freelist.

Definition at line 528 of file virtqueue.

References desc(), initialize_rings(), L4virtio::Virtqueue::num(), and L4virtio::Virtqueue::setup().

Referenced by L4virtio::Driver::Virtio_net_device::setup_device(), and L4virtio::Driver::Block_device::setup_device().

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◆ initialize_rings()

void L4virtio::Driver::Virtqueue::initialize_rings ( unsigned num )

inline

Initialize the descriptor table and the index structures of this queue.

Parameters

num	The number of entries in the descriptor table, the available ring, and the used ring (must be a power of 2).

Precondition: The queue must be set up correctly with setup() or setup_simple().

Definition at line 500 of file virtqueue.

References L4virtio::Virtqueue::_avail, L4virtio::Virtqueue::_desc, L4virtio::Virtqueue::_used, L4virtio::Virtqueue::Avail::idx, L4virtio::Virtqueue::Used::idx, L4virtio::Virtqueue::Desc::next, and L4virtio::Virtqueue::num().

Referenced by init_queue(), and init_queue().

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The documentation for this class was generated from the following file:

l4/l4virtio/virtqueue

Public Member Functions

Additional Inherited Members

Detailed Description

Member Function Documentation

◆ alloc_descriptor()

◆ desc()

◆ enqueue_descriptor()

◆ find_next_used()

◆ free_descriptor()

◆ init_queue() [1/2]

◆ init_queue() [2/2]

◆ initialize_rings()