xen: Move tsc reliability check until after CPUs have booted

AMD CPUs by default enable X86_FEATURE_TSC_RELIABLE, and depend upon a
later check to disable this feature if TSC drift is detected.
Unfortunately, this check is done in time.c:init_xen_time(), which is
done before any secondary CPUs are brought up, and is thus guaranteed
to succed.

This patch moves the check into its own function, and calls it after
cpus are brought up.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
xen-unstable changeset:   23846:bf2aaf21e8e7
xen-unstable date:        Sat Sep 17 16:22:54 2011 +0100

xen/arch/x86/setup.c

@@ -1266,8 +1266,11 @@ void __init __start_xen(unsigned long mbi_p)
     printk("Brought up %ld CPUs\n", (long)num_online_cpus());
     smp_cpus_done(max_cpus);
 
+    verify_tsc_reliability();
+
     do_initcalls();
 
+
     if ( opt_watchdog ) 
         watchdog_enable();
     

xen/arch/x86/time.c

@@ -1445,8 +1445,8 @@ static void __init tsc_check_writability(void)
     disable_tsc_sync = 1;
 }
 
-/* Late init function (after all CPUs are booted). */
-int __init init_xen_time(void)
+/* Late init function, after all cpus have booted */
+void __init verify_tsc_reliability(void)
 {
     if ( boot_cpu_has(X86_FEATURE_TSC_RELIABLE) )
     {
@@ -1458,9 +1458,17 @@ int __init init_xen_time(void)
          */
         tsc_check_reliability();
         if ( tsc_max_warp )
+        {
+            printk("%s: TSC warp detected, disabling TSC_RELIABLE\n",
+                   __func__);
             setup_clear_cpu_cap(X86_FEATURE_TSC_RELIABLE);
+        }
     }
+}
 
+/* Late init function (after interrupts are enabled). */
+int __init init_xen_time(void)
+{
     tsc_check_writability();
 
     /* If we have constant-rate TSCs then scale factor can be shared. */

xen/include/xen/time.h

@@ -11,6 +11,7 @@
 #include <xen/types.h>
 #include <public/xen.h>
 
+extern void verify_tsc_reliability(void);
 extern int init_xen_time(void);
 extern void cstate_restore_tsc(void);