[PATCH v8 22/24] iommu: Add ops->domain_alloc_paging()

[Jason Gunthorpe]

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
IOMMU_DOMAIN_DMA.

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
this.

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>
Reviewed-by: Lu Baolu <baolu.lu at linux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel at redhat.com>
Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
---
 drivers/iommu/iommu.c | 17 ++++++++++++++---
 include/linux/iommu.h |  3 +++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 38856d542afc35..fe033043be467a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2041,6 +2041,7 @@ void iommu_set_fault_handler(struct iommu_domain *domain,
 EXPORT_SYMBOL_GPL(iommu_set_fault_handler);
 
 static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
+						 struct device *dev,
 						 unsigned int type)
 {
 	struct iommu_domain *domain;
@@ -2048,8 +2049,13 @@ 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 && ops->domain_alloc_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;
 
@@ -2074,14 +2080,19 @@ static struct iommu_domain *__iommu_domain_alloc(const struct iommu_ops *ops,
 static struct iommu_domain *
 __iommu_group_domain_alloc(struct iommu_group *group, unsigned int type)
 {
-	return __iommu_domain_alloc(group_iommu_ops(group), type);
+	struct device *dev =
+		list_first_entry(&group->devices, struct group_device, list)
+			->dev;
+
+	return __iommu_domain_alloc(group_iommu_ops(group), 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,
+				    IOMMU_DOMAIN_UNMANAGED);
 }
 EXPORT_SYMBOL_GPL(iommu_domain_alloc);
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 511dfeea527215..3f173307434dcc 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -239,6 +239,8 @@ struct iommu_iotlb_gather {
  *           use. The information type is one of enum iommu_hw_info_type defined
  *           in include/uapi/linux/iommufd.h.
  * @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
@@ -273,6 +275,7 @@ 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);
-- 
2.42.0