iommu/s390: Get rid of s390_domain_device

The struct s390_domain_device serves the sole purpose as list entry for
the devices list of a struct s390_domain. As it contains no additional
information besides a list_head and a pointer to the struct zpci_dev we
can simplify things and just thread the device list through struct
zpci_dev directly. This removes the need to allocate during domain
attach and gets rid of one level of indirection during mapping
operations.

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Link: https://lore.kernel.org/r/20221025115657.1666860-3-schnelle@linux.ibm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

arch/s390/include/asm/pci.h

@@ -117,6 +117,7 @@ struct zpci_bus {
 struct zpci_dev {
 	struct zpci_bus *zbus;
 	struct list_head entry;		/* list of all zpci_devices, needed for hotplug, etc. */
+	struct list_head iommu_list;
 	struct kref kref;
 	struct hotplug_slot hotplug_slot;
 

drivers/iommu/s390-iommu.c

@@ -29,11 +29,6 @@ struct s390_domain {
 	spinlock_t		list_lock;
 };
 
-struct s390_domain_device {
-	struct list_head	list;
-	struct zpci_dev		*zdev;
-};
-
 static struct s390_domain *to_s390_domain(struct iommu_domain *dom)
 {
 	return container_of(dom, struct s390_domain, domain);
@@ -87,21 +82,13 @@ static void s390_domain_free(struct iommu_domain *domain)
 static void __s390_iommu_detach_device(struct zpci_dev *zdev)
 {
 	struct s390_domain *s390_domain = zdev->s390_domain;
-	struct s390_domain_device *domain_device, *tmp;
 	unsigned long flags;
 
 	if (!s390_domain)
 		return;
 
 	spin_lock_irqsave(&s390_domain->list_lock, flags);
-	list_for_each_entry_safe(domain_device, tmp, &s390_domain->devices,
-				 list) {
-		if (domain_device->zdev == zdev) {
-			list_del(&domain_device->list);
-			kfree(domain_device);
-			break;
-		}
-	}
+	list_del_init(&zdev->iommu_list);
 	spin_unlock_irqrestore(&s390_domain->list_lock, flags);
 
 	zpci_unregister_ioat(zdev, 0);
@@ -114,28 +101,21 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 {
 	struct s390_domain *s390_domain = to_s390_domain(domain);
 	struct zpci_dev *zdev = to_zpci_dev(dev);
-	struct s390_domain_device *domain_device;
 	unsigned long flags;
 	int cc, rc = 0;
 
 	if (!zdev)
 		return -ENODEV;
 
-	domain_device = kzalloc(sizeof(*domain_device), GFP_KERNEL);
-	if (!domain_device)
-		return -ENOMEM;
-
 	if (zdev->s390_domain)
 		__s390_iommu_detach_device(zdev);
 	else if (zdev->dma_table)
 		zpci_dma_exit_device(zdev);
 
 	cc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
 				virt_to_phys(s390_domain->dma_table));
-	if (cc) {
-		rc = -EIO;
-		goto out_free;
-	}
+	if (cc)
+		return -EIO;
 	zdev->dma_table = s390_domain->dma_table;
 
 	spin_lock_irqsave(&s390_domain->list_lock, flags);
@@ -151,18 +131,15 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 		rc = -EINVAL;
 		goto out_unregister;
 	}
-	domain_device->zdev = zdev;
 	zdev->s390_domain = s390_domain;
-	list_add(&domain_device->list, &s390_domain->devices);
+	list_add(&zdev->iommu_list, &s390_domain->devices);
 	spin_unlock_irqrestore(&s390_domain->list_lock, flags);
 
 	return 0;
 
 out_unregister:
 	zpci_unregister_ioat(zdev, 0);
 	zdev->dma_table = NULL;
-out_free:
-	kfree(domain_device);
 
 	return rc;
 }
@@ -206,10 +183,10 @@ static int s390_iommu_update_trans(struct s390_domain *s390_domain,
 				   phys_addr_t pa, dma_addr_t dma_addr,
 				   size_t size, int flags)
 {
-	struct s390_domain_device *domain_device;
 	phys_addr_t page_addr = pa & PAGE_MASK;
 	dma_addr_t start_dma_addr = dma_addr;
 	unsigned long irq_flags, nr_pages, i;
+	struct zpci_dev *zdev;
 	unsigned long *entry;
 	int rc = 0;
 
@@ -234,8 +211,8 @@ static int s390_iommu_update_trans(struct s390_domain *s390_domain,
 	}
 
 	spin_lock(&s390_domain->list_lock);
-	list_for_each_entry(domain_device, &s390_domain->devices, list) {
-		rc = zpci_refresh_trans((u64) domain_device->zdev->fh << 32,
+	list_for_each_entry(zdev, &s390_domain->devices, iommu_list) {
+		rc = zpci_refresh_trans((u64)zdev->fh << 32,
 					start_dma_addr, nr_pages * PAGE_SIZE);
 		if (rc)
 			break;