[PATCH 1/3] iommu/s390: Fix duplicate domain attachments

Niklas Schnelle
2022-09-15T15:20:18Z

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.
This also makes the restore behavior analogous between IOMMU and DMA API
control.

Fixes: fa7e9ecc5e1c ("iommu/s390: Tolerate repeat attach_dev calls")
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
drivers/iommu/s390-iommu.c | 82 ++++++++++++++++++++++----------------
1 file changed, 47 insertions(+), 35 deletions(-)

diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index c898bcbbce11..de8f76775240 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -83,14 +83,41 @@ static void s390_domain_free(struct iommu_domain *domain)
kfree(s390_domain);
}

+static bool __s390_iommu_detach_device(struct s390_domain *s390_domain,
+ struct zpci_dev *zdev)
+{
+ struct s390_domain_device *domain_device, *tmp;
+ unsigned long flags;
+ bool found = false;
+
+ 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 = true;
+ break;
+ }
+ }
+ spin_unlock_irqrestore(&s390_domain->list_lock, flags);
+
+ if (found) {
+ zdev->s390_domain = NULL;
+ zpci_unregister_ioat(zdev, 0);
+ }
+ return found;
+}
+
static int s390_iommu_attach_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;
+ struct s390_domain *prev_domain = NULL;
unsigned long flags;
- int cc, rc;
+ int cc, rc = 0;

if (!zdev)
return -ENODEV;
@@ -99,16 +126,16 @@ 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) {
+ if (zdev->s390_domain) {
+ prev_domain = zdev->s390_domain;
+ if (!__s390_iommu_detach_device(zdev->s390_domain, zdev))
+ rc = -EIO;
+ } else if (zdev->dma_table) {
+ if (zpci_dma_exit_device(zdev))
rc = -EIO;
- goto out_free;
- }
}
-
- if (zdev->s390_domain)
- zpci_unregister_ioat(zdev, 0);
+ if (rc)
+ goto out_free;

zdev->dma_table = s390_domain->dma_table;
cc = zpci_register_ioat(zdev, 0, zdev->start_dma, zdev->end_dma,
@@ -129,7 +156,7 @@ 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_unregister_restore;
}
domain_device->zdev = zdev;
zdev->s390_domain = s390_domain;
@@ -138,14 +165,15 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,

return 0;

+out_unregister_restore:
+ zpci_unregister_ioat(zdev, 0);
out_restore:
- if (!zdev->s390_domain) {
+ zdev->dma_table = NULL;
+ if (prev_domain)
+ s390_iommu_attach_device(&prev_domain->domain,
+ dev);
+ else
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 +185,14 @@ 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;
+ bool detached;

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);
+ detached = __s390_iommu_detach_device(s390_domain, zdev);
+ if (detached)
zpci_dma_init_device(zdev);
- }
}

static struct iommu_device *s390_iommu_probe_device(struct device *dev)
--
2.34.1