[PATCH RFC 1/6] public/xen.h: add flags field to vcpu_time_info

[Joao Martins <joao.m.martins@oracle.com>]

This field has two possible flags (as of latest pvclock ABI
shared with KVM).

flags: bits in this field indicate extended capabilities
coordinated between the guest and the hypervisor.  Specifically
on KVM, availability of specific flags has to be checked in
0x40000001 cpuid leaf. On Xen, we don't have that but we can
still check some of the flags after registering the time info
page since a force_update_vcpu_system_time is performed.

Current flags are:

 flag bit   | cpuid bit    | meaning
-------------------------------------------------------------
            |              | time measures taken across
     0      |      24      | multiple cpus are guaranteed to
            |              | be monotonic
-------------------------------------------------------------
            |              | guest vcpu has been paused by
     1      |     N/A      | the host
            |              |
-------------------------------------------------------------

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 xen/include/public/xen.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
index ff5547e..1223686 100644
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -601,10 +601,14 @@ struct vcpu_time_info {
      */
     uint32_t tsc_to_system_mul;
     int8_t   tsc_shift;
-    int8_t   pad1[3];
+    int8_t   flags;
+    int8_t   pad1[2];
 }; /* 32 bytes */
 typedef struct vcpu_time_info vcpu_time_info_t;
 
+#define PVCLOCK_TSC_STABLE_BIT	(1 << 0)
+#define PVCLOCK_GUEST_STOPPED	(1 << 1)
+
 struct vcpu_info {
     /*
      * 'evtchn_upcall_pending' is written non-zero by Xen to indicate
-- 
2.1.4