iommu/amd: Refactor amd_iommu_domain_enable_v2 to remove locking

The current function to enable IOMMU v2 also lock the domain.
In order to reuse the same code in different code path, in which
the domain has already been locked, refactor the function to separate
the locking from the enabling logic.

Co-developed-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20220825063939.8360-5-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd/iommu.c

@@ -85,6 +85,7 @@ struct iommu_cmd {
 struct kmem_cache *amd_iommu_irq_cache;
 
 static void detach_device(struct device *dev);
+static int domain_enable_v2(struct protection_domain *domain, int pasids);
 
 /****************************************************************************
  *
@@ -2450,11 +2451,10 @@ void amd_iommu_domain_direct_map(struct iommu_domain *dom)
 }
 EXPORT_SYMBOL(amd_iommu_domain_direct_map);
 
-int amd_iommu_domain_enable_v2(struct iommu_domain *dom, int pasids)
+/* Note: This function expects iommu_domain->lock to be held prior calling the function. */
+static int domain_enable_v2(struct protection_domain *domain, int pasids)
 {
-	struct protection_domain *domain = to_pdomain(dom);
-	unsigned long flags;
-	int levels, ret;
+	int levels;
 
 	/* Number of GCR3 table levels required */
 	for (levels = 0; (pasids - 1) & ~0x1ff; pasids >>= 9)
@@ -2463,32 +2463,40 @@ int amd_iommu_domain_enable_v2(struct iommu_domain *dom, int pasids)
 	if (levels > amd_iommu_max_glx_val)
 		return -EINVAL;
 
-	spin_lock_irqsave(&domain->lock, flags);
+	domain->gcr3_tbl = (void *)get_zeroed_page(GFP_ATOMIC);
+	if (domain->gcr3_tbl == NULL)
+		return -ENOMEM;
+
+	domain->glx      = levels;
+	domain->flags   |= PD_IOMMUV2_MASK;
+
+	amd_iommu_domain_update(domain);
+
+	return 0;
+}
+
+int amd_iommu_domain_enable_v2(struct iommu_domain *dom, int pasids)
+{
+	struct protection_domain *pdom = to_pdomain(dom);
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&pdom->lock, flags);
 
 	/*
 	 * Save us all sanity checks whether devices already in the
 	 * domain support IOMMUv2. Just force that the domain has no
 	 * devices attached when it is switched into IOMMUv2 mode.
 	 */
 	ret = -EBUSY;
-	if (domain->dev_cnt > 0 || domain->flags & PD_IOMMUV2_MASK)
-		goto out;
-
-	ret = -ENOMEM;
-	domain->gcr3_tbl = (void *)get_zeroed_page(GFP_ATOMIC);
-	if (domain->gcr3_tbl == NULL)
+	if (pdom->dev_cnt > 0 || pdom->flags & PD_IOMMUV2_MASK)
 		goto out;
 
-	domain->glx      = levels;
-	domain->flags   |= PD_IOMMUV2_MASK;
-
-	amd_iommu_domain_update(domain);
-
-	ret = 0;
+	if (!pdom->gcr3_tbl)
+		ret = domain_enable_v2(pdom, pasids);
 
 out:
-	spin_unlock_irqrestore(&domain->lock, flags);
-
+	spin_unlock_irqrestore(&pdom->lock, flags);
 	return ret;
 }
 EXPORT_SYMBOL(amd_iommu_domain_enable_v2);