OvmfPkg/Include/IndustryStandard/Xen/event_channel.h

   1 /******************************************************************************
   2  * event_channel.h
   3  *
   4  * Event channels between domains.
   5  *
   6  * SPDX-License-Identifier: MIT
   7  *
   8  * Copyright (c) 2003-2004, K A Fraser.
   9  */
  10
  11 #ifndef __XEN_PUBLIC_EVENT_CHANNEL_H__
  12 #define __XEN_PUBLIC_EVENT_CHANNEL_H__
  13
  14 #include "xen.h"
  15
  16 /*
  17  * `incontents 150 evtchn Event Channels
  18  *
  19  * Event channels are the basic primitive provided by Xen for event
  20  * notifications. An event is the Xen equivalent of a hardware
  21  * interrupt. They essentially store one bit of information, the event
  22  * of interest is signalled by transitioning this bit from 0 to 1.
  23  *
  24  * Notifications are received by a guest via an upcall from Xen,
  25  * indicating when an event arrives (setting the bit). Further
  26  * notifications are masked until the bit is cleared again (therefore,
  27  * guests must check the value of the bit after re-enabling event
  28  * delivery to ensure no missed notifications).
  29  *
  30  * Event notifications can be masked by setting a flag; this is
  31  * equivalent to disabling interrupts and can be used to ensure
  32  * atomicity of certain operations in the guest kernel.
  33  *
  34  * Event channels are represented by the evtchn_* fields in
  35  * struct shared_info and struct vcpu_info.
  36  */
  37
  38 /*
  39  * ` enum neg_errnoval
  40  * ` HYPERVISOR_event_channel_op(enum event_channel_op cmd, VOID *args)
  41  * `
  42  * @cmd  == EVTCHNOP_* (event-channel operation).
  43  * @args == struct evtchn_* Operation-specific extra arguments (NULL if none).
  44  */
  45
  46 /* ` enum event_channel_op { // EVTCHNOP_* => struct evtchn_* */
  47 #define EVTCHNOP_close          3
  48 #define EVTCHNOP_send           4
  49 #define EVTCHNOP_alloc_unbound  6
  50 /* ` } */
  51
  52 typedef UINT32 evtchn_port_t;
  53 DEFINE_XEN_GUEST_HANDLE (evtchn_port_t);
  54
  55 /*
  56  * EVTCHNOP_alloc_unbound: Allocate a port in domain <dom> and mark as
  57  * accepting interdomain bindings from domain <remote_dom>. A fresh port
  58  * is allocated in <dom> and returned as <port>.
  59  * NOTES:
  60  *  1. If the caller is unprivileged then <dom> must be DOMID_SELF.
  61  *  2. <rdom> may be DOMID_SELF, allowing loopback connections.
  62  */
  63 struct evtchn_alloc_unbound {
  64   /* IN parameters */
  65   domid_t          dom, remote_dom;
  66   /* OUT parameters */
  67   evtchn_port_t    port;
  68 };
  69
  70 typedef struct evtchn_alloc_unbound evtchn_alloc_unbound_t;
  71
  72 /*
  73  * EVTCHNOP_close: Close a local event channel <port>. If the channel is
  74  * interdomain then the remote end is placed in the unbound state
  75  * (EVTCHNSTAT_unbound), awaiting a new connection.
  76  */
  77 struct evtchn_close {
  78   /* IN parameters. */
  79   evtchn_port_t    port;
  80 };
  81
  82 typedef struct evtchn_close evtchn_close_t;
  83
  84 /*
  85  * EVTCHNOP_send: Send an event to the remote end of the channel whose local
  86  * endpoint is <port>.
  87  */
  88 struct evtchn_send {
  89   /* IN parameters. */
  90   evtchn_port_t    port;
  91 };
  92
  93 typedef struct evtchn_send evtchn_send_t;
  94
  95 #endif /* __XEN_PUBLIC_EVENT_CHANNEL_H__ */
  96
  97 /*
  98  * Local variables:
  99  * mode: C
 100  * c-file-style: "BSD"
 101  * c-basic-offset: 4
 102  * tab-width: 4
 103  * indent-tabs-mode: nil
 104  * End:
 105  */