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@linux.intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
  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;