@@ -21,6 +21,11 @@
*/
#define KVM_FEATURE_CLOCKSOURCE2 3
+/* The last 8 bits are used to indicate how to interpret the flags field
+ * in pvclock structure. If no bits are set, all flags are ignored.
+ */
+#define KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24
+
#define MSR_KVM_WALL_CLOCK 0x11
#define MSR_KVM_SYSTEM_TIME 0x12
@@ -39,5 +39,6 @@ struct pvclock_wall_clock {
u32 nsec;
} __attribute__((__packed__));
+#define PVCLOCK_TSC_STABLE_BIT (1 << 0)
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_PVCLOCK_ABI_H */
@@ -215,4 +215,7 @@ void __init kvmclock_init(void)
clocksource_register(&kvm_clock);
pv_info.paravirt_enabled = 1;
pv_info.name = "KVM";
+
+ if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
+ pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
}
@@ -135,6 +135,10 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
barrier();
} while (version != src->version);
+ if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
+ (shadow.flags & PVCLOCK_TSC_STABLE_BIT))
+ return ret;
+
/*
* Assumption here is that last_value, a global accumulator, always goes
* forward. If we are less than that, we should not be much smaller.