[PATCH] x86/time: Correctly update the domain watchdog in the shared info page

[Andrew Cooper <andrew.cooper3@citrix.com>]

For a normal HVM domain on 64bit Xen, the shared info switches to 32bit for
hvmloader, then to the native size for the HVM guest.  This guarantees at
least one transition during which the wallclock information will be updated.

The wallclock for each domain gets updated when dom0 issues a XENPF_settime
hypercall to updated the wallclock base time.

However, for a 64bit domain on 64bit Xen which is resuming from S4,
(i.e. bypassing hvmloader), there are no transitions in the size of the shared
info page, meaning that before the next XENPF_settime from dom0, the domU PV
drivers will find the Unix Epoch in the wallclock rather than the correct
time.

Therefore, manually set the watchdog when creating the domain, so it is set
right from the start of the domain, and when manually adjusting the domain
time offset, as it depends on the same value which has just been adjusted.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
CC: Paul Durrant <Paul.Durrant@citrix.com>
---
This fixes a bug presence since Xen gained 64bit support, which had been
hacked around in a gross way in XenServer.

It should be backported to all stable releases.
---
 xen/arch/x86/domain.c |    1 +
 xen/arch/x86/time.c   |    1 +
 2 files changed, 2 insertions(+)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 874742c..664d598 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -546,6 +546,7 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags)
         clear_page(d->shared_info);
         share_xen_page_with_guest(
             virt_to_page(d->shared_info), d, XENSHARE_writable);
+        update_domain_wallclock_time(d);
 
         if ( (rc = init_domain_irq_mapping(d)) != 0 )
             goto fail;
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index cf8bc78..f047cb3 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -931,6 +931,7 @@ void domain_set_time_offset(struct domain *d, int32_t time_offset_seconds)
     d->time_offset_seconds = time_offset_seconds;
     if ( is_hvm_domain(d) )
         rtc_update_clock(d);
+    update_domain_wallclock_time(d);
 }
 
 int cpu_frequency_change(u64 freq)
-- 
1.7.10.4