[RFC PATCH 1/1] xsm: allows system domains to allocate evtchn

["Daniel P. Smith" <dpsmith@apertussolutions.com>]

During domain construction under dom0less and hyperlaunch it is necessary to
allocate at least the event channel for xenstore and potentially the event
channel for the core console. When dom0less and hyperlaunch are doing their
construction logic they are executing under the idle domain context. The idle
domain is not a privileged domain, it is not the target domain, and as a result
under the current default XSM policy is not allowed to allocate the event
channel.

This patch only addresses the event channel situation by adjust the default XSM
policy for xsm_evtchn_unbound to explicitly allow system domains to be able to
make the allocation call.

Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
---
 xen/common/event_channel.c | 4 ++--
 xen/include/xsm/dummy.h    | 8 ++++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index ffb042a241..c9c3876ee9 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -306,7 +306,7 @@ static int evtchn_alloc_unbound(evtchn_alloc_unbound_t *alloc)
         ERROR_EXIT_DOM(port, d);
     chn = evtchn_from_port(d, port);
 
-    rc = xsm_evtchn_unbound(XSM_TARGET, d, chn, alloc->remote_dom);
+    rc = xsm_evtchn_unbound(XSM_OTHER, d, chn, alloc->remote_dom);
     if ( rc )
         goto out;
 
@@ -1366,7 +1366,7 @@ int alloc_unbound_xen_event_channel(
         goto out;
     chn = evtchn_from_port(ld, port);
 
-    rc = xsm_evtchn_unbound(XSM_TARGET, ld, chn, remote_domid);
+    rc = xsm_evtchn_unbound(XSM_OTHER, ld, chn, remote_domid);
     if ( rc )
         goto out;
 
diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index 58afc1d589..bd31ce43f9 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -294,8 +294,12 @@ static XSM_INLINE int cf_check xsm_claim_pages(XSM_DEFAULT_ARG struct domain *d)
 static XSM_INLINE int cf_check xsm_evtchn_unbound(
     XSM_DEFAULT_ARG struct domain *d, struct evtchn *chn, domid_t id2)
 {
-    XSM_ASSERT_ACTION(XSM_TARGET);
-    return xsm_default_action(action, current->domain, d);
+    XSM_ASSERT_ACTION(XSM_OTHER);
+
+    if ( is_system_domain(current->domain) )
+        return xsm_default_action(XSM_HOOK, current->domain, d);
+    else
+        return xsm_default_action(XSM_TARGET, current->domain, d);
 }
 
 static XSM_INLINE int cf_check xsm_evtchn_interdomain(
-- 
2.20.1