---

yaml
---
r: 120822
b: refs/heads/master
c: eca0cd0
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 88b094fb8d4fe43b7025ea8d487059e8813e02cd
+refs/heads/master: eca0cd028bdf0f6aaceb0d023e9c7501079a7dda

trunk/arch/x86/include/asm/vmware.h

@@ -22,5 +22,6 @@
 
 extern unsigned long vmware_get_tsc_khz(void);
 extern int vmware_platform(void);
+extern void vmware_set_feature_bits(struct cpuinfo_x86 *c);
 
 #endif

trunk/arch/x86/kernel/cpu/hypervisor.c

@@ -41,8 +41,17 @@ unsigned long get_hypervisor_tsc_freq(void)
 	return 0;
 }
 
+static inline void __cpuinit
+hypervisor_set_feature_bits(struct cpuinfo_x86 *c)
+{
+	if (boot_cpu_data.x86_hyper_vendor == X86_HYPER_VENDOR_VMWARE) {
+		vmware_set_feature_bits(c);
+		return;
+	}
+}
+
 void __cpuinit init_hypervisor(struct cpuinfo_x86 *c)
 {
 	detect_hypervisor_vendor(c);
+	hypervisor_set_feature_bits(c);
 }
-

trunk/arch/x86/kernel/cpu/vmware.c

@@ -86,3 +86,21 @@ unsigned long vmware_get_tsc_khz(void)
 	BUG_ON(!vmware_platform());
 	return __vmware_get_tsc_khz();
 }
+
+/*
+ * VMware hypervisor takes care of exporting a reliable TSC to the guest.
+ * Still, due to timing difference when running on virtual cpus, the TSC can
+ * be marked as unstable in some cases. For example, the TSC sync check at
+ * bootup can fail due to a marginal offset between vcpus' TSCs (though the
+ * TSCs do not drift from each other).  Also, the ACPI PM timer clocksource
+ * is not suitable as a watchdog when running on a hypervisor because the
+ * kernel may miss a wrap of the counter if the vcpu is descheduled for a
+ * long time. To skip these checks at runtime we set these capability bits,
+ * so that the kernel could just trust the hypervisor with providing a
+ * reliable virtual TSC that is suitable for timekeeping.
+ */
+void __cpuinit vmware_set_feature_bits(struct cpuinfo_x86 *c)
+{
+	set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
+	set_cpu_cap(c, X86_FEATURE_TSC_RELIABLE);
+}

trunk/arch/x86/kernel/tsc_sync.c

@@ -108,6 +108,12 @@ void __cpuinit check_tsc_sync_source(int cpu)
 	if (unsynchronized_tsc())
 		return;
 
+	if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
+		printk(KERN_INFO
+		       "Skipping synchronization checks as TSC is reliable.\n");
+		return;
+	}
+
 	printk(KERN_INFO "checking TSC synchronization [CPU#%d -> CPU#%d]:",
 			  smp_processor_id(), cpu);
 
@@ -161,7 +167,7 @@ void __cpuinit check_tsc_sync_target(void)
 {
 	int cpus = 2;
 
-	if (unsynchronized_tsc())
+	if (unsynchronized_tsc() || boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
 		return;
 
 	/*