[PATCH v2 7/8] iommu: Retire bus ops

Robin Murphy
2023-01-26T18:26:59Z

With the rest of the API internals converted, it's time to finally
tackle probe_device and how we bootstrap the per-device ops association
to begin with. This ends up being disappointingly straightforward, since
fwspec users are already doing it in order to find their of_xlate
callback, and it works out that we can easily do the equivalent for
other drivers too. Then shuffle the remaining awareness of iommu_ops
into the couple of core headers that still need it, and breathe a sigh
of relief.

Ding dong the bus ops are gone!

CC: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CC: Christoph Hellwig <hch@lst.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v2: Clarify the iommu_ops_from_fwnode(NULL) assumption [Baolu]

drivers/iommu/iommu.c | 28 +++++++++++++++++-----------
include/acpi/acpi_bus.h | 2 ++
include/linux/device.h | 1 -
include/linux/device/bus.h | 5 -----
include/linux/dma-map-ops.h | 1 +
5 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index bdc5fdf39d2b..7fb7c84e3dc6 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -219,13 +219,6 @@ int iommu_device_register(struct iommu_device *iommu,
/* 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)
@@ -235,10 +228,8 @@ int iommu_device_register(struct iommu_device *iommu,
list_add_tail(&iommu->list, &iommu_device_list);
spin_unlock(&iommu_device_lock);

- for (int i = 0; i < ARRAY_SIZE(iommu_buses) && !err; i++) {
- iommu_buses[i]->iommu_ops = ops;
+ for (int i = 0; i < ARRAY_SIZE(iommu_buses) && !err; i++)
err = bus_iommu_probe(iommu_buses[i]);
- }
if (err)
iommu_device_unregister(iommu);
return err;
@@ -310,12 +301,27 @@ static u32 dev_iommu_get_max_pasids(struct device *dev)

static int __iommu_probe_device(struct device *dev, struct list_head *group_list)
{
- const struct iommu_ops *ops = dev->bus->iommu_ops;
+ const struct iommu_ops *ops;
struct iommu_device *iommu_dev;
+ struct iommu_fwspec *fwspec;
struct iommu_group *group;
static DEFINE_MUTEX(iommu_probe_device_lock);
int ret;

+ /*
+ * For FDT-based systems and ACPI IORT/VIOT, drivers register IOMMU
+ * instances with non-NULL fwnodes, and client devices should have been
+ * identified with a fwspec by this point. Otherwise, we can currently
+ * assume that only one of Intel, AMD, s390, PAMU or legacy SMMUv2 can
+ * be present, and that any of their registered instances has suitable
+ * ops for probing, and thus cheekily co-opt the same mechanism.
+ */
+ fwspec = dev_iommu_fwspec_get(dev);
+ if (fwspec && fwspec->ops)
+ ops = fwspec->ops;
+ else
+ ops = iommu_ops_from_fwnode(NULL);
+
if (!ops)
return -ENODEV;
/*
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index cd3b75e08ec3..067dde9291c9 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -614,6 +614,8 @@ struct acpi_pci_root {

/* helper */

+struct iommu_ops;
+
bool acpi_dma_supported(const struct acpi_device *adev);
enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev);
int acpi_iommu_fwspec_init(struct device *dev, u32 id,
diff --git a/include/linux/device.h b/include/linux/device.h
index 44e3acae7b36..f7a7ecafedd3 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -41,7 +41,6 @@ struct class;
struct subsys_private;
struct device_node;
struct fwnode_handle;
-struct iommu_ops;
struct iommu_group;
struct dev_pin_info;
struct dev_iommu;
diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
index d8b29ccd07e5..4ece3470112f 100644
--- a/include/linux/device/bus.h
+++ b/include/linux/device/bus.h
@@ -63,9 +63,6 @@ struct fwnode_handle;
* this bus.
* @pm: Power management operations of this bus, callback the specific
* device driver's pm-ops.
- * @iommu_ops: IOMMU specific operations for this bus, used to attach IOMMU
- * driver implementations to a bus and allow the driver to do
- * bus-specific setup
* @p: The private data of the driver core, only the driver core can
* touch this.
* @lock_key: Lock class key for use by the lock validator
@@ -109,8 +106,6 @@ struct bus_type {

const struct dev_pm_ops *pm;

- const struct iommu_ops *iommu_ops;
-
struct subsys_private *p;
struct lock_class_key lock_key;

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index d678afeb8a13..e8ebf0bf611b 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -10,6 +10,7 @@
#include <linux/pgtable.h>

struct cma;
+struct iommu_ops;

/*
* Values for struct dma_map_ops.flags:
--
2.36.1.dirty