Ensure that the storing of the offset and the reading of the TSC
are never preempted by taking a spinlock. While the lock is overkill
now, it is useful later in this patch series.
/*
- * writes 'guest_tsc' into guest's timestamp counter "register"
- * guest_tsc = host_tsc + tsc_offset ==> tsc_offset = guest_tsc - host_tsc
+ * writes 'offset' into guest's timestamp counter offset register
*/
-static void guest_write_tsc(u64 guest_tsc, u64 host_tsc)
+static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
{
- vmcs_write64(TSC_OFFSET, guest_tsc - host_tsc);
+ vmcs_write64(TSC_OFFSET, offset);
}
+void guest_write_tsc(struct kvm_vcpu *vcpu, u64 data)
+{
+ struct kvm *kvm = vcpu->kvm;
+ u64 offset;
+
+ spin_lock(&kvm->arch.tsc_write_lock);
+ offset = data - native_read_tsc();
+ kvm_x86_ops->write_tsc_offset(vcpu, offset);
+ spin_unlock(&kvm->arch.tsc_write_lock);
+
+ /* Reset of TSC must disable overshoot protection below */
+ vcpu->arch.hv_clock.tsc_timestamp = 0;
+}
+EXPORT_SYMBOL_GPL(guest_write_tsc);
+