src/include/xen/event_channel.h

/* SPDX-License-Identifier: MIT */
/******************************************************************************
 * event_channel.h
 *
 * Event channels between domains.
 *
 * Copyright (c) 2003-2004, K A Fraser.
 */

#ifndef __XEN_PUBLIC_EVENT_CHANNEL_H__
#define __XEN_PUBLIC_EVENT_CHANNEL_H__

FILE_LICENCE ( MIT );

#include "xen.h"

/*
 * `incontents 150 evtchn 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.
 */

/*
 * ` enum neg_errnoval
 * ` HYPERVISOR_event_channel_op(enum event_channel_op cmd, void *args)
 * `
 * @cmd  == EVTCHNOP_* (event-channel operation).
 * @args == struct evtchn_* Operation-specific extra arguments (NULL if none).
 */

/* ` enum event_channel_op { // EVTCHNOP_* => struct evtchn_* */
#define EVTCHNOP_bind_interdomain 0
#define EVTCHNOP_bind_virq        1
#define EVTCHNOP_bind_pirq        2
#define EVTCHNOP_close            3
#define EVTCHNOP_send             4
#define EVTCHNOP_status           5
#define EVTCHNOP_alloc_unbound    6
#define EVTCHNOP_bind_ipi         7
#define EVTCHNOP_bind_vcpu        8
#define EVTCHNOP_unmask           9
#define EVTCHNOP_reset           10
#define EVTCHNOP_init_control    11
#define EVTCHNOP_expand_array    12
#define EVTCHNOP_set_priority    13
#ifdef __XEN__
#define EVTCHNOP_reset_cont      14
#endif
/* ` } */

typedef uint32_t evtchn_port_t;
DEFINE_XEN_GUEST_HANDLE(evtchn_port_t);

/*
 * EVTCHNOP_alloc_unbound: Allocate a port in domain <dom> and mark as
 * accepting interdomain bindings from domain <remote_dom>. A fresh port
 * is allocated in <dom> and returned as <port>.
 * NOTES:
 *  1. If the caller is unprivileged then <dom> must be DOMID_SELF.
 *  2. <remote_dom> may be DOMID_SELF, allowing loopback connections.
 */
struct evtchn_alloc_unbound {
    /* IN parameters */
    domid_t dom, remote_dom;
    /* OUT parameters */
    evtchn_port_t port;
};
typedef struct evtchn_alloc_unbound evtchn_alloc_unbound_t;

/*
 * EVTCHNOP_bind_interdomain: Construct an interdomain event channel between
 * the calling domain and <remote_dom>. <remote_dom,remote_port> must identify
 * a port that is unbound and marked as accepting bindings from the calling
 * domain. A fresh port is allocated in the calling domain and returned as
 * <local_port>.
 *
 * In case the peer domain has already tried to set our event channel
 * pending, before it was bound, EVTCHNOP_bind_interdomain always sets
 * the local event channel pending.
 *
 * The usual pattern of use, in the guest's upcall (or subsequent
 * handler) is as follows: (Re-enable the event channel for subsequent
 * signalling and then) check for the existence of whatever condition
 * is being waited for by other means, and take whatever action is
 * needed (if any).
 *
 * NOTES:
 *  1. <remote_dom> may be DOMID_SELF, allowing loopback connections.
 */
struct evtchn_bind_interdomain {
    /* IN parameters. */
    domid_t remote_dom;
    evtchn_port_t remote_port;
    /* OUT parameters. */
    evtchn_port_t local_port;
};
typedef struct evtchn_bind_interdomain evtchn_bind_interdomain_t;

/*
 * EVTCHNOP_bind_virq: Bind a local event channel to VIRQ <irq> on specified
 * vcpu.
 * NOTES:
 *  1. Virtual IRQs are classified as per-vcpu or global. See the VIRQ list
 *     in xen.h for the classification of each VIRQ.
 *  2. Global VIRQs must be allocated on VCPU0 but can subsequently be
 *     re-bound via EVTCHNOP_bind_vcpu.
 *  3. Per-vcpu VIRQs may be bound to at most one event channel per vcpu.
 *     The allocated event channel is bound to the specified vcpu and the
 *     binding cannot be changed.
 */
struct evtchn_bind_virq {
    /* IN parameters. */
    uint32_t virq; /* enum virq */
    uint32_t vcpu;
    /* OUT parameters. */
    evtchn_port_t port;
};
typedef struct evtchn_bind_virq evtchn_bind_virq_t;

/*
 * EVTCHNOP_bind_pirq: Bind a local event channel to a real IRQ (PIRQ <irq>).
 * NOTES:
 *  1. A physical IRQ may be bound to at most one event channel per domain.
 *  2. Only a sufficiently-privileged domain may bind to a physical IRQ.
 */
struct evtchn_bind_pirq {
    /* IN parameters. */
    uint32_t pirq;
#define BIND_PIRQ__WILL_SHARE 1
    uint32_t flags; /* BIND_PIRQ__* */
    /* OUT parameters. */
    evtchn_port_t port;
};
typedef struct evtchn_bind_pirq evtchn_bind_pirq_t;

/*
 * EVTCHNOP_bind_ipi: Bind a local event channel to receive events.
 * NOTES:
 *  1. The allocated event channel is bound to the specified vcpu. The binding
 *     may not be changed.
 */
struct evtchn_bind_ipi {
    uint32_t vcpu;
    /* OUT parameters. */
    evtchn_port_t port;
};
typedef struct evtchn_bind_ipi evtchn_bind_ipi_t;

/*
 * EVTCHNOP_close: Close a local event channel <port>. If the channel is
 * interdomain then the remote end is placed in the unbound state
 * (EVTCHNSTAT_unbound), awaiting a new connection.
 */
struct evtchn_close {
    /* IN parameters. */
    evtchn_port_t port;
};
typedef struct evtchn_close evtchn_close_t;

/*
 * EVTCHNOP_send: Send an event to the remote end of the channel whose local
 * endpoint is <port>.
 */
struct evtchn_send {
    /* IN parameters. */
    evtchn_port_t port;
};
typedef struct evtchn_send evtchn_send_t;

/*
 * EVTCHNOP_status: Get the current status of the communication channel which
 * has an endpoint at <dom, port>.
 * NOTES:
 *  1. <dom> may be specified as DOMID_SELF.
 *  2. Only a sufficiently-privileged domain may obtain the status of an event
 *     channel for which <dom> is not DOMID_SELF.
 */
struct evtchn_status {
    /* IN parameters */
    domid_t  dom;
    evtchn_port_t port;
    /* OUT parameters */
#define EVTCHNSTAT_closed       0  /* Channel is not in use.                 */
#define EVTCHNSTAT_unbound      1  /* Channel is waiting interdom connection.*/
#define EVTCHNSTAT_interdomain  2  /* Channel is connected to remote domain. */
#define EVTCHNSTAT_pirq         3  /* Channel is bound to a phys IRQ line.   */
#define EVTCHNSTAT_virq         4  /* Channel is bound to a virtual IRQ line */
#define EVTCHNSTAT_ipi          5  /* Channel is bound to a virtual IPI line */
    uint32_t status;
    uint32_t vcpu;                 /* VCPU to which this channel is bound.   */
    union {
        struct {
            domid_t dom;
        } unbound;                 /* EVTCHNSTAT_unbound */
        struct {
            domid_t dom;
            evtchn_port_t port;
        } interdomain;             /* EVTCHNSTAT_interdomain */
        uint32_t pirq;             /* EVTCHNSTAT_pirq        */
        uint32_t virq;             /* EVTCHNSTAT_virq        */
    } u;
};
typedef struct evtchn_status evtchn_status_t;

/*
 * EVTCHNOP_bind_vcpu: Specify which vcpu a channel should notify when an
 * event is pending.
 * NOTES:
 *  1. IPI-bound channels always notify the vcpu specified at bind time.
 *     This binding cannot be changed.
 *  2. Per-VCPU VIRQ channels always notify the vcpu specified at bind time.
 *     This binding cannot be changed.
 *  3. All other channels notify vcpu0 by default. This default is set when
 *     the channel is allocated (a port that is freed and subsequently reused
 *     has its binding reset to vcpu0).
 */
struct evtchn_bind_vcpu {
    /* IN parameters. */
    evtchn_port_t port;
    uint32_t vcpu;
};
typedef struct evtchn_bind_vcpu evtchn_bind_vcpu_t;

/*
 * EVTCHNOP_unmask: Unmask the specified local event-channel port and deliver
 * a notification to the appropriate VCPU if an event is pending.
 */
struct evtchn_unmask {
    /* IN parameters. */
    evtchn_port_t port;
};
typedef struct evtchn_unmask evtchn_unmask_t;

/*
 * EVTCHNOP_reset: Close all event channels associated with specified domain.
 * NOTES:
 *  1. <dom> may be specified as DOMID_SELF.
 *  2. Only a sufficiently-privileged domain may specify other than DOMID_SELF.
 *  3. Destroys all control blocks and event array, resets event channel
 *     operations to 2-level ABI if called with <dom> == DOMID_SELF and FIFO
 *     ABI was used. Guests should not bind events during EVTCHNOP_reset call
 *     as these events are likely to be lost.
 */
struct evtchn_reset {
    /* IN parameters. */
    domid_t dom;
};
typedef struct evtchn_reset evtchn_reset_t;

/*
 * EVTCHNOP_init_control: initialize the control block for the FIFO ABI.
 *
 * Note: any events that are currently pending will not be resent and
 * will be lost.  Guests should call this before binding any event to
 * avoid losing any events.
 */
struct evtchn_init_control {
    /* IN parameters. */
    uint64_t control_gfn;
    uint32_t offset;
    uint32_t vcpu;
    /* OUT parameters. */
    uint8_t link_bits;
    uint8_t _pad[7];
};
typedef struct evtchn_init_control evtchn_init_control_t;

/*
 * EVTCHNOP_expand_array: add an additional page to the event array.
 */
struct evtchn_expand_array {
    /* IN parameters. */
    uint64_t array_gfn;
};
typedef struct evtchn_expand_array evtchn_expand_array_t;

/*
 * EVTCHNOP_set_priority: set the priority for an event channel.
 */
struct evtchn_set_priority {
    /* IN parameters. */
    evtchn_port_t port;
    uint32_t priority;
};
typedef struct evtchn_set_priority evtchn_set_priority_t;

/*
 * ` enum neg_errnoval
 * ` HYPERVISOR_event_channel_op_compat(struct evtchn_op *op)
 * `
 * Superceded by new event_channel_op() hypercall since 0x00030202.
 */
struct evtchn_op {
    uint32_t cmd; /* enum event_channel_op */
    union {
        evtchn_alloc_unbound_t    alloc_unbound;
        evtchn_bind_interdomain_t bind_interdomain;
        evtchn_bind_virq_t        bind_virq;
        evtchn_bind_pirq_t        bind_pirq;
        evtchn_bind_ipi_t         bind_ipi;
        evtchn_close_t            close;
        evtchn_send_t             send;
        evtchn_status_t           status;
        evtchn_bind_vcpu_t        bind_vcpu;
        evtchn_unmask_t           unmask;
    } u;
};
typedef struct evtchn_op evtchn_op_t;
DEFINE_XEN_GUEST_HANDLE(evtchn_op_t);

/*
 * 2-level ABI
 */

#define EVTCHN_2L_NR_CHANNELS (sizeof(xen_ulong_t) * sizeof(xen_ulong_t) * 64)

/*
 * FIFO ABI
 */

/* Events may have priorities from 0 (highest) to 15 (lowest). */
#define EVTCHN_FIFO_PRIORITY_MAX     0
#define EVTCHN_FIFO_PRIORITY_DEFAULT 7
#define EVTCHN_FIFO_PRIORITY_MIN     15

#define EVTCHN_FIFO_MAX_QUEUES (EVTCHN_FIFO_PRIORITY_MIN + 1)

typedef uint32_t event_word_t;

#define EVTCHN_FIFO_PENDING 31
#define EVTCHN_FIFO_MASKED  30
#define EVTCHN_FIFO_LINKED  29
#define EVTCHN_FIFO_BUSY    28

#define EVTCHN_FIFO_LINK_BITS 17
#define EVTCHN_FIFO_LINK_MASK ((1 << EVTCHN_FIFO_LINK_BITS) - 1)

#define EVTCHN_FIFO_NR_CHANNELS (1 << EVTCHN_FIFO_LINK_BITS)

struct evtchn_fifo_control_block {
    uint32_t ready;
    uint32_t _rsvd;
    uint32_t head[EVTCHN_FIFO_MAX_QUEUES];
};
typedef struct evtchn_fifo_control_block evtchn_fifo_control_block_t;

#endif /* __XEN_PUBLIC_EVENT_CHANNEL_H__ */

/*
 * Local variables:
 * mode: C
 * c-file-style: "BSD"
 * c-basic-offset: 4
 * tab-width: 4
 * indent-tabs-mode: nil
 * End:
 */