OvmfPkg/XenBusDxe: Add Event Channel Notify.

This first function is used to notify the other side that there is
something to do. The other side is another Xen domain.

Change in V4:
- Replace the license by the commonly used file header text.

Change in V3:
- Return error code from hypercall instead of ASSERT for
  XenEventChannelNotify
- moving event_channel.h to this patch.

Change in V2:
- file header
- coding style
- adding comment to functions
- Licenses

License: This patch adds event_channel.h which is under MIT licence.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16265 6f19259b-4bc3-4df7-8a09-765794883524

OvmfPkg/Include/IndustryStandard/Xen/event_channel.h

@@ -0,0 +1,118 @@
+/******************************************************************************
+ * event_channel.h
+ *
+ * Event channels between domains.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Copyright (c) 2003-2004, K A Fraser.
+ */
+
+#ifndef __XEN_PUBLIC_EVENT_CHANNEL_H__
+#define __XEN_PUBLIC_EVENT_CHANNEL_H__
+
+#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_close            3
+#define EVTCHNOP_send             4
+#define EVTCHNOP_alloc_unbound    6
+/* ` } */
+
+typedef UINT32 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. <rdom> 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_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;
+
+#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:
+ */