[PATCH 18/20] iommu: Add ops->domain_alloc_paging()

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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.

Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
 drivers/iommu/iommu.c | 40 ++++++++++++++++++++++++----------------
 include/linux/iommu.h |  2 ++
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index f20a031e2910b2..fee417df8f195d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -93,6 +93,7 @@ static int iommu_bus_notifier(struct notifier_block *nb,
 			      unsigned long action, void *data);
 static void iommu_release_device(struct device *dev);
 static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+						 struct device *dev,
 						 unsigned type);
 static int __iommu_attach_device(struct iommu_domain *domain,
 				 struct device *dev);
@@ -1618,12 +1619,12 @@ static int iommu_get_def_domain_type(struct device *dev)
 }
 
 static struct iommu_domain *
-__iommu_group_alloc_default_domain(struct bus_type *bus,
+__iommu_group_alloc_default_domain(struct group_device *gdev,
 				   struct iommu_group *group, int req_type)
 {
 	if (group->default_domain && group->default_domain->type == req_type)
 		return group->default_domain;
-	return __iommu_domain_alloc(bus, req_type);
+	return __iommu_domain_alloc(gdev->dev->bus, gdev->dev, req_type);
 }
 
 /*
@@ -1633,9 +1634,9 @@ __iommu_group_alloc_default_domain(struct bus_type *bus,
 static struct iommu_domain *
 iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 {
-	struct bus_type *bus =
-		list_first_entry(&group->devices, struct group_device, list)
-			->dev->bus;
+	struct group_device *gdev =
+		list_first_entry(&group->devices, struct group_device, list);
+	const struct iommu_ops *ops = dev_iommu_ops(gdev->dev);
 	struct iommu_domain *dom;
 
 	lockdep_assert_held(&group->mutex);
@@ -1645,14 +1646,15 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 	 * domain. This should always be either an IDENTITY or PLATFORM domain.
 	 * Do not use in new drivers.
 	 */
-	if (bus->iommu_ops->default_domain) {
+	if (ops->default_domain) {
 		if (req_type)
 			return ERR_PTR(-EINVAL);
-		return bus->iommu_ops->default_domain;
+		return ops->default_domain;
 	}
 
 	if (req_type)
-		return __iommu_group_alloc_default_domain(bus, group, req_type);
+		return __iommu_group_alloc_default_domain(gdev, group,
+							  req_type);
 
 	/*
 	 * If ARM32 CONFIG_ARM_DMA_USE_IOMMU is enabled and the driver doesn't
@@ -1665,18 +1667,19 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 				IS_ENABLED(CONFIG_IOMMU_DMA)));
 
 		return __iommu_group_alloc_default_domain(
-			bus, group, IOMMU_DOMAIN_IDENTITY);
+			gdev, group, IOMMU_DOMAIN_IDENTITY);
 	}
 
 	/* The driver gave no guidance on what type to use, try the default */
-	dom = __iommu_group_alloc_default_domain(bus, group, iommu_def_domain_type);
+	dom = __iommu_group_alloc_default_domain(gdev, group,
+						 iommu_def_domain_type);
 	if (dom)
 		return dom;
 
 	/* Otherwise IDENTITY and DMA_FQ defaults will try DMA */
 	if (iommu_def_domain_type == IOMMU_DOMAIN_DMA)
 		return NULL;
-	dom = __iommu_group_alloc_default_domain(bus, group, IOMMU_DOMAIN_DMA);
+	dom = __iommu_group_alloc_default_domain(gdev, group, IOMMU_DOMAIN_DMA);
 	if (!dom)
 		return NULL;
 
@@ -1930,6 +1933,7 @@ void iommu_set_fault_handler(struct iommu_domain *domain,
 EXPORT_SYMBOL_GPL(iommu_set_fault_handler);
 
 static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+						 struct device *dev,
 						 unsigned type)
 {
 	struct iommu_domain *domain;
@@ -1940,7 +1944,11 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
 	if (type == IOMMU_DOMAIN_IDENTITY && bus->iommu_ops->identity_domain)
 		return bus->iommu_ops->identity_domain;
 
-	domain = bus->iommu_ops->domain_alloc(type);
+	if ((type == IOMMU_DOMAIN_UNMANAGED || type == IOMMU_DOMAIN_DMA) &&
+	    bus->iommu_ops->domain_alloc_paging)
+		domain = bus->iommu_ops->domain_alloc_paging(dev);
+	else
+		domain = bus->iommu_ops->domain_alloc(type);
 	if (!domain)
 		return NULL;
 
@@ -1964,7 +1972,7 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
 
 struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
 {
-	return __iommu_domain_alloc(bus, IOMMU_DOMAIN_UNMANAGED);
+	return __iommu_domain_alloc(bus, NULL, IOMMU_DOMAIN_UNMANAGED);
 }
 EXPORT_SYMBOL_GPL(iommu_domain_alloc);
 
@@ -3079,15 +3087,15 @@ static int __iommu_group_alloc_blocking_domain(struct iommu_group *group)
 	if (group->blocking_domain)
 		return 0;
 
-	group->blocking_domain =
-		__iommu_domain_alloc(dev->dev->bus, IOMMU_DOMAIN_BLOCKED);
+	group->blocking_domain = __iommu_domain_alloc(dev->dev->bus, dev->dev,
+						      IOMMU_DOMAIN_BLOCKED);
 	if (!group->blocking_domain) {
 		/*
 		 * For drivers that do not yet understand IOMMU_DOMAIN_BLOCKED
 		 * create an empty domain instead.
 		 */
 		group->blocking_domain = __iommu_domain_alloc(
-			dev->dev->bus, IOMMU_DOMAIN_UNMANAGED);
+			dev->dev->bus, dev->dev, IOMMU_DOMAIN_UNMANAGED);
 		if (!group->blocking_domain)
 			return -EINVAL;
 	}
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index f6a28ab78e607e..cc9aff2d213eec 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -227,6 +227,7 @@ 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_UNMANAGED
  * @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
@@ -258,6 +259,7 @@ 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);
-- 
2.40.0




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