[PATCH v3 1/5] iommu/s390: Fix duplicate domain attachments

[Niklas Schnelle]

Since commit fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev
calls") we can end up with duplicates in the list of devices attached to
a domain. This is inefficient and confusing since only one domain can
actually be in control of the IOMMU translations for a device. Fix this
by detaching the device from the previous domain, if any, on attach.
Add a WARN_ON() in case we still have attached devices on freeing the
domain. While here remove the re-attach on failure dance as it was
determined to be unlikely to help and may confuse debug and recovery.

Fixes: fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev calls")
Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
---
Changes since v2:
- Make __s390_iommu_detach_device() return void (Jason)
- Remove superfluous locking when we're freeing anyway (Jason)
- Remove the re-attach on failure dance as it is unlikely to help
  and complicates debug and recovery (Jason)
- Ignore attempts to detach from domain that the device is no longer
  attached to.

 drivers/iommu/s390-iommu.c | 77 +++++++++++++++++---------------------
 1 file changed, 34 insertions(+), 43 deletions(-)

diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index c898bcbbce11..6fcb64e4b5e6 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -79,10 +79,36 @@ static void s390_domain_free(struct iommu_domain *domain)
 {
 	struct s390_domain *s390_domain = to_s390_domain(domain);
 
+	WARN_ON(!list_empty(&s390_domain->devices));
 	dma_cleanup_tables(s390_domain->dma_table);
 	kfree(s390_domain);
 }
 
+static void __s390_iommu_detach_device(struct s390_domain *s390_domain,
+				       struct zpci_dev *zdev)
+{
+	struct s390_domain_device *domain_device, *tmp;
+	unsigned long flags;
+
+	if (!zdev || zdev->s390_domain != 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;
+		}
+	}
+	spin_unlock_irqrestore(&s390_domain->list_lock, flags);
+
+	zpci_unregister_ioat(zdev, 0);
+	zdev->s390_domain = NULL;
+	zdev->dma_table = NULL;
+}
+
 static int s390_iommu_attach_device(struct iommu_domain *domain,
 				    struct device *dev)
 {
@@ -90,7 +116,7 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 	struct zpci_dev *zdev = to_zpci_dev(dev);
 	struct s390_domain_device *domain_device;
 	unsigned long flags;
-	int cc, rc;
+	int cc, rc = 0;
 
 	if (!zdev)
 		return -ENODEV;
@@ -99,23 +125,17 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 	if (!domain_device)
 		return -ENOMEM;
 
-	if (zdev->dma_table && !zdev->s390_domain) {
-		cc = zpci_dma_exit_device(zdev);
-		if (cc) {
-			rc = -EIO;
-			goto out_free;
-		}
-	}
-
 	if (zdev->s390_domain)
-		zpci_unregister_ioat(zdev, 0);
+		__s390_iommu_detach_device(zdev->s390_domain, zdev);
+	else if (zdev->dma_table)
+		zpci_dma_exit_device(zdev);
 
 	zdev->dma_table = s390_domain->dma_table;
 	cc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
 				virt_to_phys(zdev->dma_table));
 	if (cc) {
 		rc = -EIO;
-		goto out_restore;
+		goto out_free;
 	}
 
 	spin_lock_irqsave(&s390_domain->list_lock, flags);
@@ -129,7 +149,7 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 		   domain->geometry.aperture_end != zdev->end_dma) {
 		rc = -EINVAL;
 		spin_unlock_irqrestore(&s390_domain->list_lock, flags);
-		goto out_restore;
+		goto out_free;
 	}
 	domain_device->zdev = zdev;
 	zdev->s390_domain = s390_domain;
@@ -138,14 +158,6 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 
 	return 0;
 
-out_restore:
-	if (!zdev->s390_domain) {
-		zpci_dma_init_device(zdev);
-	} else {
-		zdev->dma_table = zdev->s390_domain->dma_table;
-		zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
-				   virt_to_phys(zdev->dma_table));
-	}
 out_free:
 	kfree(domain_device);
 
@@ -157,30 +169,9 @@ static void s390_iommu_detach_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, *tmp;
-	unsigned long flags;
-	int found = 0;
-
-	if (!zdev)
-		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);
-			found = 1;
-			break;
-		}
-	}
-	spin_unlock_irqrestore(&s390_domain->list_lock, flags);
 
-	if (found && (zdev->s390_domain == s390_domain)) {
-		zdev->s390_domain = NULL;
-		zpci_unregister_ioat(zdev, 0);
-		zpci_dma_init_device(zdev);
-	}
+	__s390_iommu_detach_device(s390_domain, zdev);
+	zpci_dma_init_device(zdev);
 }
 
 static struct iommu_device *s390_iommu_probe_device(struct device *dev)
-- 
2.34.1