Revert "ANDROID: KVM: arm64: iommu: Allow to boot without IOMMU driver"

This reverts commit 247011a0cc.

We require an IOMMU for pVM confidentiality.

Bug: 357781595
Bug: 384432312
Change-Id: I858ed7063ef3fc02cef1155c21b7ffdf921a333e
Signed-off-by: Keir Fraser <keirf@google.com>

arch/arm64/kvm/hyp/nvhe/iommu/iommu.c

@@ -215,7 +215,7 @@ int kvm_iommu_init(struct kvm_iommu_ops *ops,
 	    !ops->init ||
 	    !ops->alloc_domain ||
 	    !ops->free_domain)
-		return 0;
+		return -ENODEV;
 
 	ret = hyp_pool_init_empty(&iommu_host_pool, 64);
 	if (ret)

arch/arm64/kvm/iommu.c

@@ -42,7 +42,7 @@ int kvm_iommu_init_driver(void)
 {
 	if (!smp_load_acquire(&iommu_driver) || !iommu_driver->get_iommu_id_by_of) {
 		kvm_err("pKVM enabled without an IOMMU driver, do not run confidential workloads in virtual machines\n");
-		return 0;
+		return -ENODEV;
 	}
 
 	kvm_hyp_iommu_domains = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,