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From:   Niklas Schnelle <schnelle@linux.ibm.com>
To:     Matthew Rosato <mjrosato@linux.ibm.com>,
        Pierre Morel <pmorel@linux.ibm.com>, iommu@lists.linux.dev
Cc:     linux-s390@vger.kernel.org, borntraeger@linux.ibm.com,
        hca@linux.ibm.com, gor@linux.ibm.com,
        gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com,
        svens@linux.ibm.com, joro@8bytes.org, will@kernel.org,
        robin.murphy@arm.com, jgg@nvidia.com, linux-kernel@vger.kernel.org
Subject: [PATCH v2 3/3] iommu/s390: Get rid of s390_domain_device
Date:   Thu, 22 Sep 2022 11:52:39 +0200
Message-Id: <20220922095239.2115309-4-schnelle@linux.ibm.com>
In-Reply-To: <20220922095239.2115309-1-schnelle@linux.ibm.com>
References: <20220922095239.2115309-1-schnelle@linux.ibm.com>
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When an s390_domain is freed without previously detaching all devices
the corresponding s390_domain_device is leaked. Instead of fixing this
leak by freeing the s390_domain_devices in s390_domain_free() do one
better and just get rid of s390_domain_device entirely by threading the
domain's device list through struct zpci_dev. This also gets rid of
a level of indirection during operations but also the allocation of
the s390_domain_device during attach thus making it more reliable under
memory pressure.

Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
Changes since v1:
- No need to iterate the devices list on detach just delete with
  the zpci_dev handle we have (Jason)
- Don't remove list entries on s390_domain_free() instead warn on
  non-empty list as part of patch 1

 arch/s390/include/asm/pci.h |  1 +
 drivers/iommu/s390-iommu.c  | 33 ++++++---------------------------
 2 files changed, 7 insertions(+), 27 deletions(-)

diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index 108e732d7b14..15f8714ca9b7 100644
--- a/arch/s390/include/asm/pci.h
+++ b/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;
 
diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 187d2c7ba9ff..e58b5d089418 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/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);
@@ -90,19 +85,11 @@ static void s390_domain_free(struct iommu_domain *domain)
 static int __s390_iommu_detach_device(struct s390_domain *s390_domain,
 				      struct zpci_dev *zdev)
 {
-	struct s390_domain_device *domain_device, *tmp;
 	unsigned long flags;
 
 	WARN_ON(zdev->s390_domain != s390_domain);
 	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);
@@ -116,7 +103,6 @@ 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;
 	struct s390_domain *prev_domain = NULL;
 	unsigned long flags;
 	int cc, rc = 0;
@@ -124,10 +110,6 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 	if (!zdev)
 		return -ENODEV;
 
-	domain_device = kzalloc(sizeof(*domain_device), GFP_KERNEL);
-	if (!domain_device)
-		return -ENOMEM;
-
 	if (zdev->s390_domain) {
 		prev_domain = zdev->s390_domain;
 		rc = __s390_iommu_detach_device(zdev->s390_domain, zdev);
@@ -136,7 +118,7 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 			rc = -EIO;
 	}
 	if (rc)
-		goto out_free;
+		return rc;
 
 	zdev->dma_table = s390_domain->dma_table;
 	cc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
@@ -159,9 +141,8 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 		spin_unlock_irqrestore(&s390_domain->list_lock, flags);
 		goto out_unregister_restore;
 	}
-	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;
@@ -175,8 +156,6 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
 					 dev);
 	else
 		zpci_dma_init_device(zdev);
-out_free:
-	kfree(domain_device);
 
 	return rc;
 }
@@ -228,10 +207,10 @@ 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;
 
@@ -256,8 +235,8 @@ 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;
-- 
2.34.1