Add flags field to VCPUOP_set_singlsehot_timer.

Flag 'future' causes Xen to check if the timeout is in the past and
return -ETIME if so.
From: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Keir Fraser <keir@xensource.com>

linux-2.6-xen-sparse/arch/i386/kernel/time-xen.c

@@ -1008,6 +1008,7 @@ static void stop_hz_timer(void)
 	}
 
 	singleshot.timeout_abs_ns = jiffies_to_st(j);
+	singleshot.flags = 0;
 	rc = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &singleshot);
 #ifdef XEN_COMPAT_030004
 	if (rc) {

xen/common/domain.c

@@ -623,6 +623,10 @@ long do_vcpu_op(int cmd, int vcpuid, XEN_GUEST_HANDLE(void) arg)
         if ( copy_from_guest(&set, arg, 1) )
             return -EFAULT;
 
+        if ( (set.flags & VCPU_SSHOTTMR_future) &&
+             (set.timeout_abs_ns < NOW()) )
+            return -ETIME;
+
         if ( v->singleshot_timer.cpu != smp_processor_id() )
         {
             stop_timer(&v->singleshot_timer);

xen/include/public/vcpu.h

@@ -150,11 +150,17 @@ DEFINE_XEN_GUEST_HANDLE(vcpu_set_periodic_timer_t);
 #define VCPUOP_set_singleshot_timer  8 /* arg == vcpu_set_singleshot_timer_t */
 #define VCPUOP_stop_singleshot_timer 9 /* arg == NULL */
 struct vcpu_set_singleshot_timer {
-    uint64_t timeout_abs_ns;
+    uint64_t timeout_abs_ns;   /* Absolute system time value in nanoseconds. */
+    uint32_t flags;            /* VCPU_SSHOTTMR_??? */
 };
 typedef struct vcpu_set_singleshot_timer vcpu_set_singleshot_timer_t;
 DEFINE_XEN_GUEST_HANDLE(vcpu_set_singleshot_timer_t);
 
+/* Flags to VCPUOP_set_singleshot_timer. */
+ /* Require the timeout to be in the future (return -ETIME if it's passed). */
+#define _VCPU_SSHOTTMR_future (0)
+#define VCPU_SSHOTTMR_future  (1U << _VCPU_SSHOTTMR_future)
+
 #endif /* __XEN_PUBLIC_VCPU_H__ */
 
 /*