[PATCH v6 02/25] iommu: Add IOMMU_DOMAIN_PLATFORM

[Jason Gunthorpe <jgg@xxxxxxxxxx>]

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.

Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
 drivers/iommu/iommu.c | 14 +++++++++++++-
 include/linux/iommu.h |  6 ++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 5e3cdc9f3a9e78..c64365169b678d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1705,6 +1705,17 @@ 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 or 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);
 
@@ -1967,7 +1978,8 @@ void iommu_domain_free(struct iommu_domain *domain)
 	if (domain->type == IOMMU_DOMAIN_SVA)
 		mmdrop(domain->mm);
 	iommu_put_dma_cookie(domain);
-	domain->ops->free(domain);
+	if (domain->ops->free)
+		domain->ops->free(domain);
 }
 EXPORT_SYMBOL_GPL(iommu_domain_free);
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e05c93b6c37fba..87aebba474e093 100644
--- a/include/linux/iommu.h
+++ b/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;
@@ -256,6 +260,7 @@ 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.
  */
 struct iommu_ops {
 	bool (*capable)(struct device *dev, enum iommu_cap);
@@ -290,6 +295,7 @@ struct iommu_ops {
 	unsigned long pgsize_bitmap;
 	struct module *owner;
 	struct iommu_domain *identity_domain;
+	struct iommu_domain *default_domain;
 };
 
 /**
-- 
2.41.0