iommu/amd: Rearrange GCR3 table setup code

Consolidate GCR3 table related code in one place so that its easy
to maintain.

Note that this patch doesn't move __set_gcr3/__clear_gcr3. We are moving
GCR3 table from per domain to per device. Following series will rework
these functions. During that time I will move these functions as well.

No functional changes intended.
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240205115615.6053-9-vasant.hegde@amd.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd/iommu.c

@@ -1714,6 +1714,38 @@ static int setup_gcr3_table(struct protection_domain *domain, int pasids)
 	return 0;
 }
 
+static u64 *__get_gcr3_pte(u64 *root, int level, u32 pasid, bool alloc)
+{
+	int index;
+	u64 *pte;
+
+	while (true) {
+
+		index = (pasid >> (9 * level)) & 0x1ff;
+		pte   = &root[index];
+
+		if (level == 0)
+			break;
+
+		if (!(*pte & GCR3_VALID)) {
+			if (!alloc)
+				return NULL;
+
+			root = (void *)get_zeroed_page(GFP_ATOMIC);
+			if (root == NULL)
+				return NULL;
+
+			*pte = iommu_virt_to_phys(root) | GCR3_VALID;
+		}
+
+		root = iommu_phys_to_virt(*pte & PAGE_MASK);
+
+		level -= 1;
+	}
+
+	return pte;
+}
+
 static void set_dte_entry(struct amd_iommu *iommu,
 			  struct iommu_dev_data *dev_data)
 {
@@ -2737,38 +2769,6 @@ int amd_iommu_flush_tlb(struct iommu_domain *dom, u32 pasid)
 	return ret;
 }
 
-static u64 *__get_gcr3_pte(u64 *root, int level, u32 pasid, bool alloc)
-{
-	int index;
-	u64 *pte;
-
-	while (true) {
-
-		index = (pasid >> (9 * level)) & 0x1ff;
-		pte   = &root[index];
-
-		if (level == 0)
-			break;
-
-		if (!(*pte & GCR3_VALID)) {
-			if (!alloc)
-				return NULL;
-
-			root = (void *)get_zeroed_page(GFP_ATOMIC);
-			if (root == NULL)
-				return NULL;
-
-			*pte = iommu_virt_to_phys(root) | GCR3_VALID;
-		}
-
-		root = iommu_phys_to_virt(*pte & PAGE_MASK);
-
-		level -= 1;
-	}
-
-	return pte;
-}
-
 static int __set_gcr3(struct protection_domain *domain, u32 pasid,
 		      unsigned long cr3)
 {