KVM: nVMX: Do not set identity page map for L2

Fiddling with CR3 for L2 is L1's job. It may set its own, different
identity map or simple leave it alone if unrestricted guest mode is
enabled. This also fixes reading back the current CR3 on L2 exits for
reporting it to L1.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -3376,8 +3376,10 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 	if (enable_ept) {
 		eptp = construct_eptp(cr3);
 		vmcs_write64(EPT_POINTER, eptp);
-		guest_cr3 = is_paging(vcpu) ? kvm_read_cr3(vcpu) :
-			vcpu->kvm->arch.ept_identity_map_addr;
+		if (is_paging(vcpu) || is_guest_mode(vcpu))
+			guest_cr3 = kvm_read_cr3(vcpu);
+		else
+			guest_cr3 = vcpu->kvm->arch.ept_identity_map_addr;
 		ept_load_pdptrs(vcpu);
 	}