x86, vmi: TSC going backwards check in vmi clocksource

Alok N Kataria · Ingo Molnar · commit 48ffc70b675a · 2009-02-20T07:53:08.000+01:00
Impact: fix time warps under vmware

Similar to the check for TSC going backwards in the TSC clocksource,
we also need this check for VMI clocksource.

Signed-off-by: Alok N Kataria &lt;akataria@vmware.com&gt;
Cc: Zachary Amsden &lt;zach@vmware.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@elte.hu&gt;
Cc: stable@kernel.org
diff --git a/arch/x86/kernel/vmiclock_32.c b/arch/x86/kernel/vmiclock_32.c
@@ -283,10 +283,13 @@ void __devinit vmi_time_ap_init(void)
 #endif
 
 /** vmi clocksource */
+static struct clocksource clocksource_vmi;
 
 static cycle_t read_real_cycles(void)
 {
-	return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
+	cycle_t ret = (cycle_t)vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
+	return ret >= clocksource_vmi.cycle_last ?
+		ret : clocksource_vmi.cycle_last;
 }
 
 static struct clocksource clocksource_vmi = {

Original file line number	Diff line number	Diff line change
`@@ -283,10 +283,13 @@ void __devinit vmi_time_ap_init(void)`
`283`	`283`	`#endif`
`284`	`284`
`285`	`285`	`/** vmi clocksource */`
	`286`	`+static struct clocksource clocksource_vmi;`
`286`	`287`
`287`	`288`	`static cycle_t read_real_cycles(void)`
`288`	`289`	`{`
`289`		`- return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);`
	`290`	`+ cycle_t ret = (cycle_t)vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);`
	`291`	`+ return ret >= clocksource_vmi.cycle_last ?`
	`292`	`+ ret : clocksource_vmi.cycle_last;`
`290`	`293`	`}`
`291`	`294`
`292`	`295`	`static struct clocksource clocksource_vmi = {`