diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | 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 4bcb120..4ff0c27 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()) { offset = kvm->arch.last_tsc_offset; pr_debug("kvm: matched tsc offset for %llu\n", data); |