4 files changed, 36 insertions, 2 deletions

diff --git a/arch/x86/include/asm/vmware.h b/arch/x86/include/asm/vmware.h
index 02dfea5aebc..c11b7e100d8 100644
--- a/arch/x86/include/asm/vmware.h
+++ b/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
diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c
index 7bd55064ffe..35ae2b75226 100644
--- a/arch/x86/kernel/cpu/hypervisor.c
+++ b/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);
 }
-
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index d5d1b75a4b7..2ac4394fcb9 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/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);
+}
diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 9ffb01c31c4..5977c40a138 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/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;
 
         /*