KVM: nVMX: Return -EINVAL when signaling failure in pre-VM-Entry helpers

Convert all top-level nested VM-Enter consistency check functions to
return 0/-EINVAL instead of failure codes, since now they can only
ever return one failure code.

This also does not give the false impression that failure information is
always consumed and/or relevant, e.g. vmx_set_nested_state() only
cares whether or not the checks were successful.

nested_check_host_control_regs() can also now be inlined into its caller,
nested_vmx_check_host_state, since the two have effectively become the
same function.

Based on a patch by Sean Christopherson.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -2595,15 +2595,12 @@ static int nested_vmx_check_controls(struct kvm_vcpu *vcpu,
 	if (nested_check_vm_execution_controls(vcpu, vmcs12) ||
 	    nested_check_vm_exit_controls(vcpu, vmcs12) ||
 	    nested_check_vm_entry_controls(vcpu, vmcs12))
-		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
+		return -EINVAL;
 
 	return 0;
 }
 
-/*
- * Checks related to Host Control Registers and MSRs
- */
-static int nested_check_host_control_regs(struct kvm_vcpu *vcpu,
+static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
 				       struct vmcs12 *vmcs12)
 {
 	bool ia32e;
@@ -2639,15 +2636,6 @@ static int nested_check_host_control_regs(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
-				       struct vmcs12 *vmcs12)
-{
-	if (nested_check_host_control_regs(vcpu, vmcs12))
-		return VMXERR_ENTRY_INVALID_HOST_STATE_FIELD;
-
-	return 0;
-}
-
 static int nested_vmx_check_vmcs_link_ptr(struct kvm_vcpu *vcpu,
 					  struct vmcs12 *vmcs12)
 {
@@ -3159,13 +3147,11 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 			launch ? VMXERR_VMLAUNCH_NONCLEAR_VMCS
 			       : VMXERR_VMRESUME_NONLAUNCHED_VMCS);
 
-	ret = nested_vmx_check_controls(vcpu, vmcs12);
-	if (ret)
-		return nested_vmx_failValid(vcpu, ret);
+	if (nested_vmx_check_controls(vcpu, vmcs12))
+		return nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
 
-	ret = nested_vmx_check_host_state(vcpu, vmcs12);
-	if (ret)
-		return nested_vmx_failValid(vcpu, ret);
+	if (nested_vmx_check_host_state(vcpu, vmcs12))
+		return nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
 
 	/*
 	 * We're finally done with prerequisite checking, and can start with