---

yaml
---
r: 333890
b: refs/heads/master
c: cb6b6df
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 1a7bbda5b1ab0e02622761305a32dc38735b90b2
+refs/heads/master: cb6b6df111e46b9d0f79eb971575fd50555f43f4

trunk/drivers/xen/xenbus/xenbus_xs.c

@@ -48,6 +48,7 @@
 #include <xen/xenbus.h>
 #include <xen/xen.h>
 #include "xenbus_comms.h"
+#include <asm/xen/hypervisor.h>
 
 struct xs_stored_msg {
 	struct list_head list;
@@ -618,14 +619,34 @@ static struct xenbus_watch *find_watch(const char *token)
 
 	return NULL;
 }
+/*
+ * Certain older XenBus toolstack cannot handle reading values that are
+ * not populated. Some Xen 3.4 installation are incapable of doing this
+ * so if we are running on anything older than 4 do not attempt to read
+ * control/platform-feature-xs_reset_watches.
+ */
+static bool xen_strict_xenbus_quirk()
+{
+	uint32_t eax, ebx, ecx, edx, base;
+
+	base = xen_cpuid_base();
+	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
 
+	if ((eax >> 16) < 4)
+		return true;
+	return false;
+
+}
 static void xs_reset_watches(void)
 {
 	int err, supported = 0;
 
 	if (!xen_hvm_domain() || xen_initial_domain())
 		return;
 
+	if (xen_strict_xenbus_quirk())
+		return;
+
 	err = xenbus_scanf(XBT_NIL, "control",
 			"platform-feature-xs_reset_watches", "%d", &supported);
 	if (err != 1 || !supported)