[PATCH v7 1/6] iommu/s390: Fix duplicate domain attachments

Niklas Schnelle
2022-10-17T12:46:41Z

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@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
v6->v7:
- Added Matt's R-b
v5->v6:
- Only set zdev->dma_table once zpci_register_ioat() succeeded (Matt)
v4->v5:
- Unregister IOAT and set zdev->dma_table on error (Matt)

drivers/iommu/s390-iommu.c | 106 ++++++++++++++++---------------------
1 file changed, 45 insertions(+), 61 deletions(-)

diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 3c071782f6f1..c2e5e81d609e 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 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;
+ }
+ }
+ 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;
@@ -99,24 +125,18 @@ 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);
+ 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));
+ virt_to_phys(s390_domain->dma_table));
if (cc) {
rc = -EIO;
- goto out_restore;
+ goto out_free;
}
+ zdev->dma_table = s390_domain->dma_table;

spin_lock_irqsave(&s390_domain->list_lock, flags);
/* First device defines the DMA range limits */
@@ -127,9 +147,9 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
/* Allow only devices with identical DMA range limits */
} else if (domain->geometry.aperture_start != zdev->start_dma ||
domain->geometry.aperture_end != zdev->end_dma) {
- rc = -EINVAL;
spin_unlock_irqrestore(&s390_domain->list_lock, flags);
- goto out_restore;
+ rc = -EINVAL;
+ goto out_unregister;
}
domain_device->zdev = zdev;
zdev->s390_domain = s390_domain;
@@ -138,14 +158,9 @@ 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_unregister:
+ zpci_unregister_ioat(zdev, 0);
+ zdev->dma_table = NULL;
out_free:
kfree(domain_device);

@@ -155,32 +170,12 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
static void s390_iommu_detach_device(struct iommu_domain *domain,
struct device *dev)
{
- 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;
+ WARN_ON(zdev->s390_domain != to_s390_domain(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);
- 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(zdev);
+ zpci_dma_init_device(zdev);
}

static struct iommu_device *s390_iommu_probe_device(struct device *dev)
@@ -198,24 +193,13 @@ static struct iommu_device *s390_iommu_probe_device(struct device *dev)
static void s390_iommu_release_device(struct device *dev)
{
struct zpci_dev *zdev = to_zpci_dev(dev);
- struct iommu_domain *domain;

/*
- * This is a workaround for a scenario where the IOMMU API common code
- * "forgets" to call the detach_dev callback: After binding a device
- * to vfio-pci and completing the VFIO_SET_IOMMU ioctl (which triggers
- * the attach_dev), removing the device via
- * "echo 1 > /sys/bus/pci/devices/.../remove" won't trigger detach_dev,
- * only release_device will be called via the BUS_NOTIFY_REMOVED_DEVICE
- * notifier.
- *
- * So let's call detach_dev from here if it hasn't been called before.
+ * release_device is expected to detach any domain currently attached
+ * to the device, but keep it attached to other devices in the group.
*/
- if (zdev && zdev->s390_domain) {
- domain = iommu_get_domain_for_dev(dev);
- if (domain)
- s390_iommu_detach_device(domain, dev);
- }
+ if (zdev)
+ __s390_iommu_detach_device(zdev);
}

static int s390_iommu_update_trans(struct s390_domain *s390_domain,
--
2.34.1