Xen devel - Apr 2013 - [PATCH] x86: don't pass negative time to gtime_to_gtsc()

scale_delta(), which is being called by that function, doesn''t cope
with that.

Also print a warning message, so hopefully we can eventually figure why
occasionally a negative value results from the calculation in the first
place.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -854,7 +854,16 @@ static void __update_vcpu_system_time(st
         if ( is_hvm_domain(d) )
         {
             struct pl_time *pl = &v->domain->arch.hvm_domain.pl_time;
+
             stime += pl->stime_offset + v->arch.hvm_vcpu.stime_offset;
+            if ( (s64)stime < 0 )
+            {
+                printk(XENLOG_G_WARNING "d%dv%d: bogus time %" PRId64
+                       " (offsets %" PRId64 "/%" PRId64
")\n",
+                       d->domain_id, v->vcpu_id, stime,
+		       pl->stime_offset, v->arch.hvm_vcpu.stime_offset);
+                stime = 0;
+            }
         }
         tsc_stamp = gtime_to_gtsc(d, stime);
     }





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On 11/04/2013 10:21, "Jan Beulich" <JBeulich@suse.com> wrote:
> scale_delta(), which is being called by that function, doesn''t
cope
> with that.
> 
> Also print a warning message, so hopefully we can eventually figure why
> occasionally a negative value results from the calculation in the first
> place.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
> --- a/xen/arch/x86/time.c
> +++ b/xen/arch/x86/time.c
> @@ -854,7 +854,16 @@ static void __update_vcpu_system_time(st
>          if ( is_hvm_domain(d) )
>          {
>              struct pl_time *pl =
&v->domain->arch.hvm_domain.pl_time;
> +
>              stime += pl->stime_offset +
v->arch.hvm_vcpu.stime_offset;
> +            if ( (s64)stime < 0 )
> +            {
> +                printk(XENLOG_G_WARNING "d%dv%d: bogus time %"
PRId64
> +                       " (offsets %" PRId64 "/%"
PRId64 ")\n",
> +                       d->domain_id, v->vcpu_id, stime,
> +         pl->stime_offset, v->arch.hvm_vcpu.stime_offset);
> +                stime = 0;
> +            }
>          }
>          tsc_stamp = gtime_to_gtsc(d, stime);
>      }
> 
> 
>