iommu/amd: Refactor protection domain allocation code

To replace if-else with switch-case statement due to increasing number of
domain types.

No functional changes intended.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Link: https://lore.kernel.org/r/20230921092147.5930-5-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: hegdevasant

drivers/iommu/amd/iommu.c

@@ -2078,24 +2078,8 @@ static struct protection_domain *protection_domain_alloc(unsigned int type)
 	struct io_pgtable_ops *pgtbl_ops;
 	struct protection_domain *domain;
 	int pgtable;
-	int mode = DEFAULT_PGTABLE_LEVEL;
 	int ret;
 
-	/*
-	 * Force IOMMU v1 page table when iommu=pt and
-	 * when allocating domain for pass-through devices.
-	 */
-	if (type == IOMMU_DOMAIN_IDENTITY) {
-		pgtable = AMD_IOMMU_V1;
-		mode = PAGE_MODE_NONE;
-	} else if (type == IOMMU_DOMAIN_UNMANAGED) {
-		pgtable = AMD_IOMMU_V1;
-	} else if (type == IOMMU_DOMAIN_DMA || type == IOMMU_DOMAIN_DMA_FQ) {
-		pgtable = amd_iommu_pgtable;
-	} else {
-		return NULL;
-	}
-
 	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
 	if (!domain)
 		return NULL;
@@ -2106,27 +2090,42 @@ static struct protection_domain *protection_domain_alloc(unsigned int type)
 
 	spin_lock_init(&domain->lock);
 	INIT_LIST_HEAD(&domain->dev_list);
+	domain->nid = NUMA_NO_NODE;
+
+	switch (type) {
+	/* No need to allocate io pgtable ops in passthrough mode */
+	case IOMMU_DOMAIN_IDENTITY:
+		return domain;
+	case IOMMU_DOMAIN_DMA:
+	case IOMMU_DOMAIN_DMA_FQ:
+		pgtable = amd_iommu_pgtable;
+		break;
+	/*
+	 * Force IOMMU v1 page table when allocating
+	 * domain for pass-through devices.
+	 */
+	case IOMMU_DOMAIN_UNMANAGED:
+		pgtable = AMD_IOMMU_V1;
+		break;
+	default:
+		goto out_err;
+	}
 
 	switch (pgtable) {
 	case AMD_IOMMU_V1:
-		ret = protection_domain_init_v1(domain, mode);
+		ret = protection_domain_init_v1(domain, DEFAULT_PGTABLE_LEVEL);
 		break;
 	case AMD_IOMMU_V2:
 		ret = protection_domain_init_v2(domain);
 		break;
 	default:
 		ret = -EINVAL;
+		break;
 	}
 
 	if (ret)
 		goto out_err;
 
-	/* No need to allocate io pgtable ops in passthrough mode */
-	if (type == IOMMU_DOMAIN_IDENTITY)
-		return domain;
-
-	domain->nid = NUMA_NO_NODE;
-
 	pgtbl_ops = alloc_io_pgtable_ops(pgtable, &domain->iop.pgtbl_cfg, domain);
 	if (!pgtbl_ops) {
 		domain_id_free(domain->id);