ia64/xen: add a necessary header file to compile include/xen/interface/xen.h

Create include/asm-ia64/pvclock-abi.h to compile which contains
the same definitions of include/asm-x86/pvclock-abi.h because ia64/xen
uses same structure.
Hopefully include/asm-x86/pvclock-abi.h would be moved to somewhere
more generic.

Another approach is to include include/asm-x86/pvclock-abi.h
from include/asm-ia64/pvclock-abi.h. But this would break
if/when x86 header files are moved under arch/x86.
So for now, same definitions are duplicated as suggested by Tony.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/include/asm/pvclock-abi.h

+/*
+ * same structure to x86's
+ * Hopefully asm-x86/pvclock-abi.h would be moved to somewhere more generic.
+ * For now, define same duplicated definitions.
+ */
+
+#ifndef _ASM_IA64__PVCLOCK_ABI_H
+#define _ASM_IA64__PVCLOCK_ABI_H
+#ifndef __ASSEMBLY__
+
+/*
+ * These structs MUST NOT be changed.
+ * They are the ABI between hypervisor and guest OS.
+ * Both Xen and KVM are using this.
+ *
+ * pvclock_vcpu_time_info holds the system time and the tsc timestamp
+ * of the last update. So the guest can use the tsc delta to get a
+ * more precise system time.  There is one per virtual cpu.
+ *
+ * pvclock_wall_clock references the point in time when the system
+ * time was zero (usually boot time), thus the guest calculates the
+ * current wall clock by adding the system time.
+ *
+ * Protocol for the "version" fields is: hypervisor raises it (making
+ * it uneven) before it starts updating the fields and raises it again
+ * (making it even) when it is done.  Thus the guest can make sure the
+ * time values it got are consistent by checking the version before
+ * and after reading them.
+ */
+
+struct pvclock_vcpu_time_info {
+	u32   version;
+	u32   pad0;
+	u64   tsc_timestamp;
+	u64   system_time;
+	u32   tsc_to_system_mul;
+	s8    tsc_shift;
+	u8    pad[3];
+} __attribute__((__packed__)); /* 32 bytes */
+
+struct pvclock_wall_clock {
+	u32   version;
+	u32   sec;
+	u32   nsec;
+} __attribute__((__packed__));
+
+#endif /* __ASSEMBLY__ */
+#endif /* _ASM_IA64__PVCLOCK_ABI_H */