fixup argo=<bool>

docs/misc/xen-command-line.pandoc

@@ -183,17 +183,17 @@ in combination with cpuidle.  This option is only expected to be useful for
 developers wishing Xen to fall back to older timing methods on newer hardware.
 
 ### argo
-> `= <boolean>`
-
-> Default: `false`
+    = List of [ <bool> ]
 
-Enable the Argo hypervisor-mediated interdomain communication mechanism.
+Controls for the Argo hypervisor-mediated interdomain communication service.
+Argo is only available when Xen is compiled with `CONFIG_ARGO` enabled.
 
-Only available if Xen is compiled with `CONFIG_ARGO` enabled.
+Argo is a interdomain communication mechanism, where Xen acts as the central
+point of authority.  Guests may register memory rings to recieve messages,
+query the status of other domains, and send messages by hypercall, all subject
+to appropriate auditing by Xen.
 
-This allows domains access to the Argo hypercall, which supports registration
-of memory rings with the hypervisor to receive messages, sending messages to
-other domains by hypercall and querying the ring status of other domains.
+* An overall boolean acts as a global control.  Argo is disabled by default.
 
 ### asid (x86)
 > `= <boolean>`

xen/common/argo.c

@@ -31,9 +31,29 @@
 DEFINE_XEN_GUEST_HANDLE(xen_argo_addr_t);
 DEFINE_XEN_GUEST_HANDLE(xen_argo_ring_t);
 
-/* Xen command line option to enable argo */
-static bool __read_mostly opt_argo_enabled;
-boolean_param("argo", opt_argo_enabled);
+static bool __read_mostly opt_argo;
+
+static int __init parse_argo(const char *s)
+{
+    const char *ss;
+    int val, rc = 0;
+
+    do {
+        ss = strchr(s, ',');
+        if ( !ss )
+            ss = strchr(s, '\0');
+
+        if ( (val = parse_bool(s, ss)) >= 0 )
+            opt_argo = val;
+        else
+            rc = -EINVAL;
+
+        s = ss + 1;
+    } while ( *ss );
+
+    return rc;
+}
+custom_param("argo", parse_argo);
 
 typedef struct argo_ring_id
 {