Take the following code in rdmsr_interception, for example. svm->next_rip = kvm_rip_read(&svm->vcpu) + 2; Yes, the canonical rdmsr instruction is two bytes. However, there is nothing in the architectural specification prohibiting useless or redundant prefixes. So, for instance, 65 66 67 67 67 0f 32 is a perfectly valid 7-byte rdmsr instruction. It looks like this code was checked in with commit 6aa8b732ca01c ("kvm: userspace interface"), with nary a word of explanation.