KVM: nVMX: add missing consistency checks for CR0 and CR4

commit 112e660 upstream.

The effective values of the guest CR0 and CR4 registers may differ from
those included in the VMCS12.  In particular, disabling EPT forces
CR4.PAE=1 and disabling unrestricted guest mode forces CR0.PG=CR0.PE=1.

Therefore, checks on these bits cannot be delegated to the processor
and must be performed by KVM.

Reported-by: Reima ISHII <ishiir@g.ecc.u-tokyo.ac.jp>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[OP: drop CC() macro calls, as tracing is not implemented in 4.19]
[OP: adjust "return -EINVAL" -> "return 1" to match current return logic]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/kvm/vmx/vmx.c

@@ -12752,7 +12752,7 @@ static int nested_vmx_check_vmcs_link_ptr(struct kvm_vcpu *vcpu,
 static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 				  u32 *exit_qual)
 {
-	bool ia32e;
+	bool ia32e = !!(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE);
 
 	*exit_qual = ENTRY_FAIL_DEFAULT;
 
@@ -12765,6 +12765,13 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		return 1;
 	}
 
+	if ((vmcs12->guest_cr0 & (X86_CR0_PG | X86_CR0_PE)) == X86_CR0_PG)
+		return 1;
+
+	if ((ia32e && !(vmcs12->guest_cr4 & X86_CR4_PAE)) ||
+	    (ia32e && !(vmcs12->guest_cr0 & X86_CR0_PG)))
+		return 1;
+
 	/*
 	 * If the load IA32_EFER VM-entry control is 1, the following checks
 	 * are performed on the field for the IA32_EFER MSR:
@@ -12776,7 +12783,6 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	 */
 	if (to_vmx(vcpu)->nested.nested_run_pending &&
 	    (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_EFER)) {
-		ia32e = (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) != 0;
 		if (!kvm_valid_efer(vcpu, vmcs12->guest_ia32_efer) ||
 		    ia32e != !!(vmcs12->guest_ia32_efer & EFER_LMA) ||
 		    ((vmcs12->guest_cr0 & X86_CR0_PG) &&