[PATCH v2 02/10] iommu: Add a lockdep assertion for remaining dev->iommu_group reads

Jason Gunthorpe
2023-07-31T17:51:06Z

The remaining reads are all in functions called under ops->device_group.

Broadly these functions are walking around the device tree (eg going up
the PCI bus tree) and are trying to de-duplicate group allocations
according to their logic.

Since these functions don't hold any particular per-device locks their
reads to dev->iommu_group are being locked by the caller's
iommu_probe_device_lock, and this explains why iommu_probe_device_lock
needs to be a global lock.

Rename iommu_probe_device_lock to dev_iommu_group_lock, make it local to
the module and annotate all the device_group helpers with
iommu_group_get_locked() that includes a lockdep to indicate that they are
special.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/iommu/iommu.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 409090eaac543a..f1c8a333553e3b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -44,6 +44,8 @@ static unsigned int iommu_def_domain_type __read_mostly;
static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT);
static u32 iommu_cmd_line __read_mostly;

+static DEFINE_MUTEX(dev_iommu_group_lock);
+
struct iommu_group {
struct kobject kobj;
struct kobject *devices_kobj;
@@ -438,7 +440,6 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
{
const struct iommu_ops *ops = dev->bus->iommu_ops;
struct iommu_group *group;
- static DEFINE_MUTEX(iommu_probe_device_lock);
struct group_device *gdev;
int ret;

@@ -451,7 +452,7 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
* probably be able to use device_lock() here to minimise the scope,
* but for now enforcing a simple global ordering is fine.
*/
- mutex_lock(&iommu_probe_device_lock);
+ mutex_lock(&dev_iommu_group_lock);

/* Device is probed already if in a group */
if (dev->iommu_group) {
@@ -497,7 +498,7 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
list_add_tail(&group->entry, group_list);
}
mutex_unlock(&group->mutex);
- mutex_unlock(&iommu_probe_device_lock);
+ mutex_unlock(&dev_iommu_group_lock);

if (dev_is_pci(dev))
iommu_dma_set_pci_32bit_workaround(dev);
@@ -512,7 +513,7 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
mutex_unlock(&group->mutex);
iommu_group_put(group);
out_unlock:
- mutex_unlock(&iommu_probe_device_lock);
+ mutex_unlock(&dev_iommu_group_lock);

return ret;
}
@@ -1219,6 +1220,12 @@ struct iommu_group *iommu_group_get(struct device *dev)
}
EXPORT_SYMBOL_GPL(iommu_group_get);

+static struct iommu_group *iommu_group_get_locked(struct device *dev)
+{
+ lockdep_assert_held(&dev_iommu_group_lock);
+ return iommu_group_get(dev);
+}
+
/**
* iommu_group_ref_get - Increment reference on a group
* @group: the group to use, must not be NULL
@@ -1532,7 +1539,7 @@ static struct iommu_group *get_pci_alias_group(struct pci_dev *pdev,
if (test_and_set_bit(pdev->devfn & 0xff, devfns))
return NULL;

- group = iommu_group_get(&pdev->dev);
+ group = iommu_group_get_locked(&pdev->dev);
if (group)
return group;

@@ -1573,7 +1580,7 @@ static int get_pci_alias_or_group(struct pci_dev *pdev, u16 alias, void *opaque)
struct group_for_pci_data *data = opaque;

data->pdev = pdev;
- data->group = iommu_group_get(&pdev->dev);
+ data->group = iommu_group_get_locked(&pdev->dev);

return data->group != NULL;
}
@@ -1629,7 +1636,7 @@ struct iommu_group *pci_device_group(struct device *dev)

pdev = bus->self;

- group = iommu_group_get(&pdev->dev);
+ group = iommu_group_get_locked(&pdev->dev);
if (group)
return group;
}
@@ -1662,7 +1669,7 @@ struct iommu_group *fsl_mc_device_group(struct device *dev)
struct device *cont_dev = fsl_mc_cont_dev(dev);
struct iommu_group *group;

- group = iommu_group_get(cont_dev);
+ group = iommu_group_get_locked(cont_dev);
if (!group)
group = iommu_group_alloc();
return group;
--
2.41.0