[XEN PATCH v2 1/2] evtchn: Add error status indicators for evtchn_status hypercall

[Matthew Barnes <matthew.barnes@xxxxxxxxx>]

When the evtchn_status hypercall fails, it is not possible to determine
the cause of the error, since the library call returns -1 to the tool
and not the errno.

Because of this, lsevtchn is unable to determine whether to continue
event channel enumeration upon an evtchn_status hypercall error.

Add error status indicators for the eventchn_status hypercall for
lsevtchn to terminate its loop on, and keep other errors as failed
hypercalls.

Signed-off-by: Matthew Barnes <matthew.barnes@xxxxxxxxx>
---
 xen/common/event_channel.c         | 12 +++++++++++-
 xen/include/public/event_channel.h |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/xen/common/event_channel.c b/xen/common/event_channel.c
index aceee0695f9f..0f11e71c3e6f 100644
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -1030,7 +1030,17 @@ int evtchn_status(evtchn_status_t *status)
 
     d = rcu_lock_domain_by_any_id(dom);
     if ( d == NULL )
-        return -ESRCH;
+    {
+        status->status = EVTCHNSTAT_dom_invalid;
+        return 0;
+    }
+
+    if ( !port_is_valid(d, port) )
+    {
+        status->status = EVTCHNSTAT_port_invalid;
+        rcu_unlock_domain(d);
+        return 0;
+    }
 
     chn = _evtchn_from_port(d, port);
     if ( !chn )
diff --git a/xen/include/public/event_channel.h 
b/xen/include/public/event_channel.h
index 0d91a1c4afab..29cbf43945b3 100644
--- a/xen/include/public/event_channel.h
+++ b/xen/include/public/event_channel.h
@@ -200,6 +200,8 @@ struct evtchn_status {
 #define EVTCHNSTAT_pirq         3  /* Channel is bound to a phys IRQ line.   */
 #define EVTCHNSTAT_virq         4  /* Channel is bound to a virtual IRQ line */
 #define EVTCHNSTAT_ipi          5  /* Channel is bound to a virtual IPI line */
+#define EVTCHNSTAT_dom_invalid  6  /* Given domain ID is not a valid domain  */
+#define EVTCHNSTAT_port_invalid 7  /* Given port is not within valid range   */
     uint32_t status;
     uint32_t vcpu;                 /* VCPU to which this channel is bound.   */
     union {
-- 
2.34.1