[PATCH v3 23/25] iommu: Add ops->domain_alloc_paging()

Jason Gunthorpe jgg at nvidia.com
Sat Jun 10 05:56:11 AEST 2023

This callback requests the driver to create only a __IOMMU_DOMAIN_PAGING
domain, so it saves a few lines in a lot of drivers needlessly checking
the type.

More critically, this allows us to sweep out all the
IOMMU_DOMAIN_UNMANAGED and IOMMU_DOMAIN_DMA checks from a lot of the
drivers, simplifying what is going on in the code and ultimately removing
the now-unused special cases in drivers where they did not support

domain_alloc_paging() should return a struct iommu_domain that is
functionally compatible with ARM_DMA_USE_IOMMU, dma-iommu.c and iommufd.

Be forwards looking and pass in a 'struct device *' argument. We can
provide this when allocating the default_domain. No drivers will look at

Tested-by: Steven Price <steven.price at arm.com>
Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>
Tested-by: Nicolin Chen <nicolinc at nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
 drivers/iommu/iommu.c | 13 ++++++++++---
 include/linux/iommu.h |  3 +++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 0346c05e108438..2cf523ff9c6f55 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1985,6 +1985,7 @@ void iommu_set_fault_handler(struct iommu_domain *domain,
 static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
+						 struct device *dev,
 						 unsigned int type)
 	struct iommu_domain *domain;
@@ -1992,8 +1993,13 @@ static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
 	if (alloc_type == IOMMU_DOMAIN_IDENTITY && ops->identity_domain)
 		return ops->identity_domain;
+	else if (type & __IOMMU_DOMAIN_PAGING) {
+		domain = ops->domain_alloc_paging(dev);
+	} else if (ops->domain_alloc)
+		domain = ops->domain_alloc(alloc_type);
+	else
+		return NULL;
-	domain = ops->domain_alloc(alloc_type);
 	if (!domain)
 		return NULL;
@@ -2024,14 +2030,15 @@ __iommu_group_domain_alloc(struct iommu_group *group, unsigned int type)
-	return __iommu_domain_alloc(dev_iommu_ops(dev), type);
+	return __iommu_domain_alloc(dev_iommu_ops(dev), dev, type);
 struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus)
 	if (bus == NULL || bus->iommu_ops == NULL)
 		return NULL;
-	return __iommu_domain_alloc(bus->iommu_ops, IOMMU_DOMAIN_UNMANAGED);
+	return __iommu_domain_alloc(bus->iommu_ops, NULL,
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 49331573f1d1f5..8e4d178c49c417 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -233,6 +233,8 @@ struct iommu_iotlb_gather {
  * struct iommu_ops - iommu ops and capabilities
  * @capable: check capability
  * @domain_alloc: allocate iommu domain
+ * @domain_alloc_paging: Allocate an iommu_domain that can be used for
+ *                       UNMANAGED, DMA, and DMA_FQ domain types.
  * @probe_device: Add device to iommu driver handling
  * @release_device: Remove device from iommu driver handling
  * @probe_finalize: Do final setup work after the device is added to an IOMMU
@@ -264,6 +266,7 @@ struct iommu_ops {
 	/* Domain allocation and freeing by the iommu driver */
 	struct iommu_domain *(*domain_alloc)(unsigned iommu_domain_type);
+	struct iommu_domain *(*domain_alloc_paging)(struct device *dev);
 	struct iommu_device *(*probe_device)(struct device *dev);
 	void (*release_device)(struct device *dev);

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