[xen staging] xen/evtchn: modify evtchn_bind_interdomain to support static evtchn

[patchbot@xxxxxxx]

commit 7ba046a538cba2bc196d9d6d609594aa3b393f94
Author:     Rahul Singh <rahul.singh@xxxxxxx>
AuthorDate: Wed Sep 7 17:27:36 2022 +0100
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Thu Sep 8 12:21:59 2022 +0100

    xen/evtchn: modify evtchn_bind_interdomain to support static evtchn
    
    Static event channel support will be added for dom0less domains. Modify
    evtchn_bind_interdomain to support static evtchn.
    
    It is necessary to have access to the evtchn_bind_interdomain function
    to do that, so make evtchn_bind_interdomain global and also make it
    __must_check.
    
    Currently evtchn_bind_interdomain() always allocates the next available
    local port. Static event channel support for dom0less domains requires
    allocating a specified port. Modify the evtchn_bind_interdomain to
    accept the port number as an argument and allocate the specified port
    if available. If the port number argument is zero, the next available
    port will be allocated.
    
    Currently evtchn_bind_interdomain() finds the local domain from
    "current->domain" pointer. evtchn_bind_interdomain() will be called from
    the XEN to create static event channel during domain creation.
    "current" pointer is not valid at that time, therefore modify the
    evtchn_bind_interdomain() to pass domain as an argument.
    
    Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/common/event_channel.c | 20 ++++++++++++++------
 xen/include/xen/event.h    |  5 +++++
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index f546e81758..f5e0b12d15 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -381,11 +381,16 @@ static void double_evtchn_unlock(struct evtchn *lchn, 
struct evtchn *rchn)
     evtchn_write_unlock(rchn);
 }
 
-static int evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
+/*
+ * If lport is zero get the next free port and allocate. If port is non-zero
+ * allocate the specified lport.
+ */
+int evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind, struct domain *ld,
+                            evtchn_port_t lport)
 {
     struct evtchn *lchn, *rchn;
-    struct domain *ld = current->domain, *rd;
-    int            lport, rc;
+    struct domain *rd;
+    int            rc;
     evtchn_port_t  rport = bind->remote_port;
     domid_t        rdom = bind->remote_dom;
 
@@ -405,8 +410,11 @@ static int 
evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind)
         write_lock(&ld->event_lock);
     }
 
-    if ( (lport = get_free_port(ld)) < 0 )
-        ERROR_EXIT(lport);
+    lport = rc = evtchn_get_port(ld, lport);
+    if ( rc < 0 )
+        ERROR_EXIT(rc);
+    rc = 0;
+
     lchn = evtchn_from_port(ld, lport);
 
     rchn = _evtchn_from_port(rd, rport);
@@ -1239,7 +1247,7 @@ long do_event_channel_op(int cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
         struct evtchn_bind_interdomain bind_interdomain;
         if ( copy_from_guest(&bind_interdomain, arg, 1) != 0 )
             return -EFAULT;
-        rc = evtchn_bind_interdomain(&bind_interdomain);
+        rc = evtchn_bind_interdomain(&bind_interdomain, current->domain, 0);
         if ( !rc && __copy_to_guest(arg, &bind_interdomain, 1) )
             rc = -EFAULT; /* Cleaning up here would be a mess! */
         break;
diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
index f31963703f..8eae9984a9 100644
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -75,6 +75,11 @@ int evtchn_allocate_port(struct domain *d, unsigned int 
port);
 int __must_check evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc,
                                       evtchn_port_t port);
 
+/* Bind an event channel port to interdomain */
+int __must_check evtchn_bind_interdomain(evtchn_bind_interdomain_t *bind,
+                                         struct domain *ld,
+                                         evtchn_port_t port);
+
 /* Unmask a local event-channel port. */
 int evtchn_unmask(unsigned int port);
 
--
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