KVM: x86: Call vcpu_load and vcpu_put in cpuid_update

cpuid_update may operate VMCS, so vcpu_load() and vcpu_put()
should be called to ensure correctness.
Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

@@ -1712,6 +1712,7 @@ static int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 	if (copy_from_user(cpuid_entries, entries,
 			   cpuid->nent * sizeof(struct kvm_cpuid_entry)))
 		goto out_free;
+	vcpu_load(vcpu);
 	for (i = 0; i < cpuid->nent; i++) {
 		vcpu->arch.cpuid_entries[i].function = cpuid_entries[i].function;
 		vcpu->arch.cpuid_entries[i].eax = cpuid_entries[i].eax;
@@ -1729,6 +1730,7 @@ static int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 	r = 0;
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops->cpuid_update(vcpu);
+	vcpu_put(vcpu);
 
 out_free:
 	vfree(cpuid_entries);
@@ -1749,9 +1751,11 @@ static int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 	if (copy_from_user(&vcpu->arch.cpuid_entries, entries,
 			   cpuid->nent * sizeof(struct kvm_cpuid_entry2)))
 		goto out;
+	vcpu_load(vcpu);
 	vcpu->arch.cpuid_nent = cpuid->nent;
 	kvm_apic_set_version(vcpu);
 	kvm_x86_ops->cpuid_update(vcpu);
+	vcpu_put(vcpu);
 	return 0;
 
 out: