forked from luck/tmp_suning_uos_patched
x86, paravirt: don't compute pvclock adjustments if we trust the tsc
If the HV told us we can fully trust the TSC, skip any correction Signed-off-by: Glauber Costa <glommer@redhat.com> Acked-by: Zachary Amsden <zamsden@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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@ -21,6 +21,11 @@
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*/
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#define KVM_FEATURE_CLOCKSOURCE2 3
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/* The last 8 bits are used to indicate how to interpret the flags field
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* in pvclock structure. If no bits are set, all flags are ignored.
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*/
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#define KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24
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#define MSR_KVM_WALL_CLOCK 0x11
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#define MSR_KVM_SYSTEM_TIME 0x12
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@ -39,5 +39,6 @@ struct pvclock_wall_clock {
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u32 nsec;
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} __attribute__((__packed__));
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#define PVCLOCK_TSC_STABLE_BIT (1 << 0)
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_X86_PVCLOCK_ABI_H */
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@ -215,4 +215,7 @@ void __init kvmclock_init(void)
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clocksource_register(&kvm_clock);
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pv_info.paravirt_enabled = 1;
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pv_info.name = "KVM";
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if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
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pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
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}
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@ -135,6 +135,10 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
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barrier();
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} while (version != src->version);
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if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
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(shadow.flags & PVCLOCK_TSC_STABLE_BIT))
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return ret;
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/*
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* Assumption here is that last_value, a global accumulator, always goes
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* forward. If we are less than that, we should not be much smaller.
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