Event Channels

group event_channels

Event channels are the basic primitive provided by Xen for event notifications. An event is the Xen equivalent of a hardware interrupt. They essentially store one bit of information, the event of interest is signalled by transitioning this bit from 0 to 1.

Notifications are received by a guest via an upcall from Xen, indicating when an event arrives (setting the bit). Further notifications are masked until the bit is cleared again (therefore, guests must check the value of the bit after re-enabling event delivery to ensure no missed notifications).

Event notifications can be masked by setting a flag; this is equivalent to disabling interrupts and can be used to ensure atomicity of certain operations in the guest kernel.

Event channels are represented by the evtchn_* fields in struct shared_info and struct vcpu_info.

Defines

EVTCHNOP_bind_interdomain 0

EVTCHNOP_bind_virq 1

EVTCHNOP_bind_pirq 2

EVTCHNOP_close 3

EVTCHNOP_send 4

EVTCHNOP_status 5

EVTCHNOP_alloc_unbound 6

EVTCHNOP_bind_ipi 7

EVTCHNOP_bind_vcpu 8

EVTCHNOP_unmask 9

EVTCHNOP_reset 10

EVTCHNOP_init_control 11

EVTCHNOP_expand_array 12

EVTCHNOP_set_priority 13

EVTCHNOP_reset_cont 14

EVTCHN_2L_NR_CHANNELS (sizeof(xen_ulong_t) * sizeof(xen_ulong_t) * 64)

EVTCHN_FIFO_PRIORITY_MAX 0

EVTCHN_FIFO_PRIORITY_DEFAULT 7

EVTCHN_FIFO_PRIORITY_MIN 15

EVTCHN_FIFO_MAX_QUEUES (EVTCHN_FIFO_PRIORITY_MIN + 1)

EVTCHN_FIFO_PENDING 31

EVTCHN_FIFO_MASKED 30

EVTCHN_FIFO_LINKED 29

EVTCHN_FIFO_BUSY 28

EVTCHN_FIFO_LINK_BITS 17

EVTCHN_FIFO_LINK_MASK ((1 << EVTCHN_FIFO_LINK_BITS) - 1)

EVTCHN_FIFO_NR_CHANNELS (1 << EVTCHN_FIFO_LINK_BITS)

Typedefs

typedef uint32_t evtchn_port_t

typedef struct evtchn_alloc_unbound evtchn_alloc_unbound_t

typedef struct evtchn_bind_interdomain evtchn_bind_interdomain_t

typedef struct evtchn_bind_virq evtchn_bind_virq_t

typedef struct evtchn_bind_pirq evtchn_bind_pirq_t

typedef struct evtchn_bind_ipi evtchn_bind_ipi_t

typedef struct evtchn_close evtchn_close_t

typedef struct evtchn_send evtchn_send_t

typedef struct evtchn_status evtchn_status_t

typedef struct evtchn_bind_vcpu evtchn_bind_vcpu_t

typedef struct evtchn_unmask evtchn_unmask_t

typedef struct evtchn_reset evtchn_reset_t

typedef struct evtchn_init_control evtchn_init_control_t

typedef struct evtchn_expand_array evtchn_expand_array_t

typedef struct evtchn_set_priority evtchn_set_priority_t

typedef struct evtchn_op evtchn_op_t

typedef uint32_t event_word_t

typedef struct evtchn_fifo_control_block evtchn_fifo_control_block_t

union __guest_handle_evtchn_port_t

#include <event_channel.h>

Public Members

evtchn_port_t* p

unsigned long q

union __guest_handle_64_evtchn_port_t

#include <event_channel.h>

Public Members

evtchn_port_t* p

uint64_t q

union __guest_handle_const_evtchn_port_t

#include <event_channel.h>

Public Members

const evtchn_port_t* p

unsigned long q

union __guest_handle_64_const_evtchn_port_t

#include <event_channel.h>

Public Members

const evtchn_port_t* p

uint64_t q

struct evtchn_status

#include <event_channel.h>

union anonymous_union_0

#include <event_channel.h>

Public Members

struct evtchn_status::anonymous_union_0::anonymous_struct_0 anonymous_union_0::unbound

struct evtchn_status::anonymous_union_0::anonymous_struct_1 anonymous_union_0::interdomain

uint32_t anonymous_union_0::pirq

uint32_t anonymous_union_0::virq

struct evtchn_op

#include <event_channel.h>

union anonymous_union_1

#include <event_channel.h>

Public Members

evtchn_alloc_unbound_t anonymous_union_1::alloc_unbound

evtchn_bind_interdomain_t anonymous_union_1::bind_interdomain

evtchn_bind_virq_t anonymous_union_1::bind_virq

evtchn_bind_pirq_t anonymous_union_1::bind_pirq

evtchn_bind_ipi_t anonymous_union_1::bind_ipi

evtchn_close_t anonymous_union_1::close

evtchn_send_t anonymous_union_1::send

evtchn_status_t anonymous_union_1::status

evtchn_bind_vcpu_t anonymous_union_1::bind_vcpu

evtchn_unmask_t anonymous_union_1::unmask

union __guest_handle_evtchn_op_t

#include <event_channel.h>

Public Members

evtchn_op_t* p

unsigned long q

union __guest_handle_64_evtchn_op_t

#include <event_channel.h>

Public Members

evtchn_op_t* p

uint64_t q

union __guest_handle_const_evtchn_op_t

#include <event_channel.h>

Public Members

const evtchn_op_t* p

unsigned long q

union __guest_handle_64_const_evtchn_op_t

#include <event_channel.h>

Public Members

const evtchn_op_t* p

uint64_t q