iommu: Add IOMMU_DOMAIN_PLATFORM

This is used when the iommu driver is taking control of the dma_ops,
currently only on S390 and power spapr. It is designed to preserve the
original ops->detach_dev() semantic that these S390 was built around.

Provide an opaque domain type and a 'default_domain' ops value that allows
the driver to trivially force any single domain as the default domain.

Update iommufd selftest to use this instead of set_platform_dma_ops

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/2-v8-81230027b2fa+9d-iommu_all_defdom_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -184,6 +184,8 @@ static const char *iommu_domain_type_str(unsigned int t)
 	case IOMMU_DOMAIN_DMA:
 	case IOMMU_DOMAIN_DMA_FQ:
 		return "Translated";
+	case IOMMU_DOMAIN_PLATFORM:
+		return "Platform";
 	default:
 		return "Unknown";
 	}
@@ -1752,6 +1754,17 @@ iommu_group_alloc_default_domain(struct iommu_group *group, int req_type)
 
 	lockdep_assert_held(&group->mutex);
 
+	/*
+	 * Allow legacy drivers to specify the domain that will be the default
+	 * domain. This should always be either an IDENTITY/BLOCKED/PLATFORM
+	 * domain. Do not use in new drivers.
+	 */
+	if (bus->iommu_ops->default_domain) {
+		if (req_type)
+			return ERR_PTR(-EINVAL);
+		return bus->iommu_ops->default_domain;
+	}
+
 	if (req_type)
 		return __iommu_group_alloc_default_domain(bus, group, req_type);
 

drivers/iommu/iommufd/selftest.c

@@ -281,14 +281,6 @@ static bool mock_domain_capable(struct device *dev, enum iommu_cap cap)
 	return cap == IOMMU_CAP_CACHE_COHERENCY;
 }
 
-static void mock_domain_set_plaform_dma_ops(struct device *dev)
-{
-	/*
-	 * mock doesn't setup default domains because we can't hook into the
-	 * normal probe path
-	 */
-}
-
 static struct iommu_device mock_iommu_device = {
 };
 
@@ -298,12 +290,16 @@ static struct iommu_device *mock_probe_device(struct device *dev)
 }
 
 static const struct iommu_ops mock_ops = {
+	/*
+	 * IOMMU_DOMAIN_BLOCKED cannot be returned from def_domain_type()
+	 * because it is zero.
+	 */
+	.default_domain = &mock_blocking_domain,
 	.owner = THIS_MODULE,
 	.pgsize_bitmap = MOCK_IO_PAGE_SIZE,
 	.hw_info = mock_domain_hw_info,
 	.domain_alloc = mock_domain_alloc,
 	.capable = mock_domain_capable,
-	.set_platform_dma_ops = mock_domain_set_plaform_dma_ops,
 	.device_group = generic_device_group,
 	.probe_device = mock_probe_device,
 	.default_domain_ops =

include/linux/iommu.h

@@ -64,6 +64,7 @@ struct iommu_domain_geometry {
 #define __IOMMU_DOMAIN_DMA_FQ	(1U << 3)  /* DMA-API uses flush queue    */
 
 #define __IOMMU_DOMAIN_SVA	(1U << 4)  /* Shared process address space */
+#define __IOMMU_DOMAIN_PLATFORM	(1U << 5)
 
 #define IOMMU_DOMAIN_ALLOC_FLAGS ~__IOMMU_DOMAIN_DMA_FQ
 /*
@@ -81,6 +82,8 @@ struct iommu_domain_geometry {
  *				  invalidation.
  *	IOMMU_DOMAIN_SVA	- DMA addresses are shared process addresses
  *				  represented by mm_struct's.
+ *	IOMMU_DOMAIN_PLATFORM	- Legacy domain for drivers that do their own
+ *				  dma_api stuff. Do not use in new drivers.
  */
 #define IOMMU_DOMAIN_BLOCKED	(0U)
 #define IOMMU_DOMAIN_IDENTITY	(__IOMMU_DOMAIN_PT)
@@ -91,6 +94,7 @@ struct iommu_domain_geometry {
 				 __IOMMU_DOMAIN_DMA_API |	\
 				 __IOMMU_DOMAIN_DMA_FQ)
 #define IOMMU_DOMAIN_SVA	(__IOMMU_DOMAIN_SVA)
+#define IOMMU_DOMAIN_PLATFORM	(__IOMMU_DOMAIN_PLATFORM)
 
 struct iommu_domain {
 	unsigned type;
@@ -262,6 +266,9 @@ struct iommu_iotlb_gather {
  * @owner: Driver module providing these ops
  * @identity_domain: An always available, always attachable identity
  *                   translation.
+ * @default_domain: If not NULL this will always be set as the default domain.
+ *                  This should be an IDENTITY/BLOCKED/PLATFORM domain.
+ *                  Do not use in new drivers.
  */
 struct iommu_ops {
 	bool (*capable)(struct device *dev, enum iommu_cap);
@@ -297,6 +304,7 @@ struct iommu_ops {
 	unsigned long pgsize_bitmap;
 	struct module *owner;
 	struct iommu_domain *identity_domain;
+	struct iommu_domain *default_domain;
 };
 
 /**