KVM: SVM: Propagate error from snp_guest_req_init() to userspace

If snp_guest_req_init() fails, return the provided error code up the
stack to userspace, e.g. so that userspace can log that KVM_SEV_INIT2
failed, as opposed to some random operation later in VM setup failing
because SNP wasn't actually enabled for the VM.

Note, KVM itself doesn't consult the return value from __sev_guest_init(),
i.e. the fallout is purely that userspace may be confused.

Fixes: 88caf54 ("KVM: SEV: Provide support for SNP_GUEST_REQUEST NAE event")
Reported-by: kernel test robot <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Closes: https://lore.kernel.org/r/[email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

Author: sean-jc

arch/x86/kvm/svm/sev.c

@@ -450,8 +450,11 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp,
 		goto e_free;
 
 	/* This needs to happen after SEV/SNP firmware initialization. */
-	if (vm_type == KVM_X86_SNP_VM && snp_guest_req_init(kvm))
-		goto e_free;
+	if (vm_type == KVM_X86_SNP_VM) {
+		ret = snp_guest_req_init(kvm);
+		if (ret)
+			goto e_free;
+	}
 
 	INIT_LIST_HEAD(&sev->regions_list);
 	INIT_LIST_HEAD(&sev->mirror_vms);