On Thu, Aug 19, 2010 at 10:07:26PM -1000, Zachary Amsden wrote: > Make the match of TSC find TSC writes that are close to each other > instead of perfectly identical; this allows the compensator to also > work in migration / suspend scenarios. > > Signed-off-by: Zachary Amsden <[email protected]> > --- > arch/x86/kvm/x86.c | 14 ++++++++++---- > 1 files changed, 10 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 52680f6..0f3e5fb 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -928,21 +928,27 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data) > struct kvm *kvm = vcpu->kvm; > u64 offset, ns, elapsed; > unsigned long flags; > + s64 sdiff; > > spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags); > offset = data - native_read_tsc(); > ns = get_kernel_ns(); > elapsed = ns - kvm->arch.last_tsc_nsec; > + sdiff = data - kvm->arch.last_tsc_write; > + if (sdiff < 0) > + sdiff = -sdiff; > > /* > - * Special case: identical write to TSC within 5 seconds of > + * Special case: close write to TSC within 5 seconds of > * another CPU is interpreted as an attempt to synchronize > - * (the 5 seconds is to accomodate host load / swapping). > + * The 5 seconds is to accomodate host load / swapping as > + * well as any reset of TSC during the boot process. > * > * In that case, for a reliable TSC, we can match TSC offsets, > - * or make a best guest using kernel_ns value. > + * or make a best guest using elapsed value. > */ > - if (data == kvm->arch.last_tsc_write && elapsed < 5ULL * NSEC_PER_SEC) { > + if (sdiff < nsec_to_cycles(5ULL * NSEC_PER_SEC) && > + elapsed < 5ULL * NSEC_PER_SEC) { > if (!check_tsc_unstable()) { Isn't 5 way too long for this case?
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