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 <[email protected]>
---
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
On Thu, Sep 29, 2022 at 05:32:58PM +0200, Niklas Schnelle wrote:
> 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 <[email protected]>
> ---
> 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)
Please drop the s390_domain from this function, it is pointless..
Calling detach_device with a mismatched domain argument is a WARN_ON
offense, the correct recovery is still to remove the domain.
And zdev can already never be null due to the call chain
Also, s390_iommu_release_device() should call this new function since
we don't want to return back to the platform DMA when releasing.
So, like this:
diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 2bad24d6cfef59..e8333a9301ec95 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -75,12 +75,12 @@ static void s390_domain_free(struct iommu_domain *domain)
kfree(s390_domain);
}
-static void __s390_iommu_detach_device(struct s390_domain *s390_domain,
- struct zpci_dev *zdev)
+static void __s390_iommu_detach_device(struct zpci_dev *zdev)
{
+ struct s390_domain *s390_domain = zdev->s390_domain;
unsigned long flags;
- if (!zdev || zdev->s390_domain != s390_domain)
+ if (!s390_domain)
return;
spin_lock_irqsave(&s390_domain->list_lock, flags);
@@ -108,7 +108,7 @@ static int s390_iommu_attach_device(struct iommu_domain *domain,
return -EINVAL;
if (zdev->s390_domain)
- __s390_iommu_detach_device(zdev->s390_domain, zdev);
+ __s390_iommu_detach_device(zdev);
else if (zdev->dma_table)
zpci_dma_exit_device(zdev);
@@ -130,10 +130,11 @@ 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);
- __s390_iommu_detach_device(s390_domain, zdev);
+ WARN_ON(zdev->s390_domain != to_s390_domain(domain));
+
+ __s390_iommu_detach_device(zdev);
zpci_dma_init_device(zdev);
}
@@ -174,21 +175,11 @@ static void s390_iommu_release_device(struct device *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,