KVM: x86: TSC reset compensation

	unsigned long irq_sources_bitmap;

	s64 kvmclock_offset;

	spinlock_t tsc_write_lock;

	u64 last_tsc_nsec;

	u64 last_tsc_offset;

	u64 last_tsc_write;

	struct kvm_xen_hvm_config xen_hvm_config;

void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)

{

	struct kvm *kvm = vcpu->kvm;

	u64 offset;

	u64 offset, ns, elapsed;

	unsigned long flags;

	struct timespec ts;

	spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);

	offset = data - native_read_tsc();

	ktime_get_ts(&ts);

	monotonic_to_bootbased(&ts);

	ns = timespec_to_ns(&ts);

	elapsed = ns - kvm->arch.last_tsc_nsec;

	/*

	 * Special case: identical 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).

	 *

	 * In that case, for a reliable TSC, we can match TSC offsets,

	 * or make a best guest using kernel_ns value.

	 */

	if (data == kvm->arch.last_tsc_write && 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);

		} else {

			u64 tsc_delta = elapsed * __get_cpu_var(cpu_tsc_khz);

			tsc_delta = tsc_delta / USEC_PER_SEC;

			offset += tsc_delta;

			pr_debug("kvm: adjusted tsc offset by %llu\n", tsc_delta);

		}

		ns = kvm->arch.last_tsc_nsec;

	}

	kvm->arch.last_tsc_nsec = ns;

	kvm->arch.last_tsc_write = data;

	kvm->arch.last_tsc_offset = offset;

	kvm_x86_ops->write_tsc_offset(vcpu, offset);

	spin_unlock_irqrestore(&kvm->arch.tsc_write_lock, flags);