[PATCH v3 04/15] iommu: Move bus setup to IOMMU device registration

Robin Murphy
2022-07-05T17:08:56Z

Move the bus setup to iommu_device_register(). This should allow
bus_iommu_probe() to be correctly replayed for multiple IOMMU instances,
and leaves bus_set_iommu() as a glorified no-op to be cleaned up next.

At this point we can also handle cleanup better than just rolling back
the most-recently-touched bus upon failure - which may release devices
owned by other already-registered instances, and still leave devices on
other buses with dangling pointers to the failed instance. Now it's easy
to clean up the exact footprint of a given instance, no more, no less.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-By: Krishna Reddy <vdumpa@nvidia.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v3: Have iommu_device_register() return -EBUSY for conflicting ops
rather than change that behaviour just yet.

drivers/iommu/iommu.c | 54 ++++++++++++++++++++++++-------------------
1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 514edc0eaa94..acb7b2ab0b79 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -180,6 +180,14 @@ static int __init iommu_subsys_init(void)
}
subsys_initcall(iommu_subsys_init);

+static int remove_iommu_group(struct device *dev, void *data)
+{
+ if (dev->iommu && dev->iommu->iommu_dev == data)
+ iommu_release_device(dev);
+
+ return 0;
+}
+
/**
* iommu_device_register() - Register an IOMMU hardware instance
* @iommu: IOMMU handle for the instance
@@ -202,12 +210,32 @@ int iommu_device_register(struct iommu_device *iommu,
spin_lock(&iommu_device_lock);
list_add_tail(&iommu->list, &iommu_device_list);
spin_unlock(&iommu_device_lock);
+
+ for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
+ struct bus_type *bus = iommu_buses[i];
+ int err;
+
+ if (bus->iommu_ops && bus->iommu_ops != ops) {
+ err = -EBUSY;
+ } else {
+ bus->iommu_ops = ops;
+ err = bus_iommu_probe(bus);
+ }
+ if (err) {
+ iommu_device_unregister(iommu);
+ return err;
+ }
+ }
+
return 0;
}
EXPORT_SYMBOL_GPL(iommu_device_register);

void iommu_device_unregister(struct iommu_device *iommu)
{
+ for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++)
+ bus_for_each_dev(iommu_buses[i], NULL, iommu, remove_iommu_group);
+
spin_lock(&iommu_device_lock);
list_del(&iommu->list);
spin_unlock(&iommu_device_lock);
@@ -1633,13 +1661,6 @@ static int probe_iommu_group(struct device *dev, void *data)
return ret;
}

-static int remove_iommu_group(struct device *dev, void *data)
-{
- iommu_release_device(dev);
-
- return 0;
-}
-
static int iommu_bus_notifier(struct notifier_block *nb,
unsigned long action, void *data)
{
@@ -1828,27 +1849,12 @@ static int iommu_bus_init(struct bus_type *bus)
*/
int bus_set_iommu(struct bus_type *bus, const struct iommu_ops *ops)
{
- int err;
-
- if (ops == NULL) {
- bus->iommu_ops = NULL;
- return 0;
- }
-
- if (bus->iommu_ops != NULL)
+ if (bus->iommu_ops && ops && bus->iommu_ops != ops)
return -EBUSY;

bus->iommu_ops = ops;

- /* Do IOMMU specific setup for this bus-type */
- err = bus_iommu_probe(bus);
- if (err) {
- /* Clean up */
- bus_for_each_dev(bus, NULL, NULL, remove_iommu_group);
- bus->iommu_ops = NULL;
- }
-
- return err;
+ return 0;
}
EXPORT_SYMBOL_GPL(bus_set_iommu);

--
2.36.1.dirty