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      1 /******************************************************************************
      2  * event_channel.h
      3  *
      4  * Event channels between domains.
      5  *
      6  * Permission is hereby granted, free of charge, to any person obtaining a copy
      7  * of this software and associated documentation files (the "Software"), to
      8  * deal in the Software without restriction, including without limitation the
      9  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
     10  * sell copies of the Software, and to permit persons to whom the Software is
     11  * furnished to do so, subject to the following conditions:
     12  *
     13  * The above copyright notice and this permission notice shall be included in
     14  * all copies or substantial portions of the Software.
     15  *
     16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     21  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     22  * DEALINGS IN THE SOFTWARE.
     23  *
     24  * Copyright (c) 2003-2004, K A Fraser.
     25  */
     26 
     27 #ifndef __XEN_PUBLIC_EVENT_CHANNEL_H__
     28 #define __XEN_PUBLIC_EVENT_CHANNEL_H__
     29 
     30 #include "xen.h"
     31 
     32 /*
     33  * `incontents 150 evtchn Event Channels
     34  *
     35  * Event channels are the basic primitive provided by Xen for event
     36  * notifications. An event is the Xen equivalent of a hardware
     37  * interrupt. They essentially store one bit of information, the event
     38  * of interest is signalled by transitioning this bit from 0 to 1.
     39  *
     40  * Notifications are received by a guest via an upcall from Xen,
     41  * indicating when an event arrives (setting the bit). Further
     42  * notifications are masked until the bit is cleared again (therefore,
     43  * guests must check the value of the bit after re-enabling event
     44  * delivery to ensure no missed notifications).
     45  *
     46  * Event notifications can be masked by setting a flag; this is
     47  * equivalent to disabling interrupts and can be used to ensure
     48  * atomicity of certain operations in the guest kernel.
     49  *
     50  * Event channels are represented by the evtchn_* fields in
     51  * struct shared_info and struct vcpu_info.
     52  */
     53 
     54 /*
     55  * ` enum neg_errnoval
     56  * ` HYPERVISOR_event_channel_op(enum event_channel_op cmd, VOID *args)
     57  * `
     58  * @cmd  == EVTCHNOP_* (event-channel operation).
     59  * @args == struct evtchn_* Operation-specific extra arguments (NULL if none).
     60  */
     61 
     62 /* ` enum event_channel_op { // EVTCHNOP_* => struct evtchn_* */
     63 #define EVTCHNOP_close            3
     64 #define EVTCHNOP_send             4
     65 #define EVTCHNOP_alloc_unbound    6
     66 /* ` } */
     67 
     68 typedef UINT32 evtchn_port_t;
     69 DEFINE_XEN_GUEST_HANDLE(evtchn_port_t);
     70 
     71 /*
     72  * EVTCHNOP_alloc_unbound: Allocate a port in domain <dom> and mark as
     73  * accepting interdomain bindings from domain <remote_dom>. A fresh port
     74  * is allocated in <dom> and returned as <port>.
     75  * NOTES:
     76  *  1. If the caller is unprivileged then <dom> must be DOMID_SELF.
     77  *  2. <rdom> may be DOMID_SELF, allowing loopback connections.
     78  */
     79 struct evtchn_alloc_unbound {
     80     /* IN parameters */
     81     domid_t dom, remote_dom;
     82     /* OUT parameters */
     83     evtchn_port_t port;
     84 };
     85 typedef struct evtchn_alloc_unbound evtchn_alloc_unbound_t;
     86 
     87 /*
     88  * EVTCHNOP_close: Close a local event channel <port>. If the channel is
     89  * interdomain then the remote end is placed in the unbound state
     90  * (EVTCHNSTAT_unbound), awaiting a new connection.
     91  */
     92 struct evtchn_close {
     93     /* IN parameters. */
     94     evtchn_port_t port;
     95 };
     96 typedef struct evtchn_close evtchn_close_t;
     97 
     98 /*
     99  * EVTCHNOP_send: Send an event to the remote end of the channel whose local
    100  * endpoint is <port>.
    101  */
    102 struct evtchn_send {
    103     /* IN parameters. */
    104     evtchn_port_t port;
    105 };
    106 typedef struct evtchn_send evtchn_send_t;
    107 
    108 #endif /* __XEN_PUBLIC_EVENT_CHANNEL_H__ */
    109 
    110 /*
    111  * Local variables:
    112  * mode: C
    113  * c-file-style: "BSD"
    114  * c-basic-offset: 4
    115  * tab-width: 4
    116  * indent-tabs-mode: nil
    117  * End:
    118  */
    119