iommu: Move bus setup to IOMMU device registration

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>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com> # s390
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com> # s390
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/d342b6f27efb5ef3e93aacaa3012d25386d74866.1660572783.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 49f0445..422d4e9 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -188,6 +188,14 @@ 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
@@ -199,9 +207,18 @@ subsys_initcall(iommu_subsys_init);
 int iommu_device_register(struct iommu_device *iommu,
                          const struct iommu_ops *ops, struct device *hwdev)
 {
+       int err = 0;
+
        /* We need to be able to take module references appropriately */
        if (WARN_ON(is_module_address((unsigned long)ops) && !ops->owner))
                return -EINVAL;
+       /*
+        * Temporarily enforce global restriction to a single driver. This was
+        * already the de-facto behaviour, since any possible combination of
+        * existing drivers would compete for at least the PCI or platform bus.
+        */
+       if (iommu_buses[0]->iommu_ops && iommu_buses[0]->iommu_ops != ops)
+               return -EBUSY;
 
        iommu->ops = ops;
        if (hwdev)
@@ -210,12 +227,22 @@ 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);
-       return 0;
+
+       for (int i = 0; i < ARRAY_SIZE(iommu_buses) && !err; i++) {
+               iommu_buses[i]->iommu_ops = ops;
+               err = bus_iommu_probe(iommu_buses[i]);
+       }
+       if (err)
+               iommu_device_unregister(iommu);
+       return err;
 }
 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);
@@ -1643,13 +1670,6 @@ 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)
 {
@@ -1821,27 +1841,12 @@ int bus_iommu_probe(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);