Re: [PATCH 03/10] iommu: Add generic_single_device_group()

This implements the common pattern seen in drivers of a single
iommu_group for the entire iommu driver. Implement this in core code
so the drivers that want this can select it from their ops.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
  drivers/iommu/iommu.c | 25 +++++++++++++++++++++++++
  include/linux/iommu.h |  3 +++
  2 files changed, 28 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 9e41ad4e3219b6..1e0c5d9a0370fb 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c

@@ -289,6 +289,9 @@ void iommu_device_unregister(struct iommu_device *iommu)
  	spin_lock(&iommu_device_lock);
  	list_del(&iommu->list);
  	spin_unlock(&iommu_device_lock);
+
+	/* Pairs with the alloc in generic_single_device_group() */
+	iommu_group_put(iommu->singleton_group);
  }
  EXPORT_SYMBOL_GPL(iommu_device_unregister);
  

@@ -1595,6 +1598,28 @@ struct iommu_group *generic_device_group(struct device *dev)
  }
  EXPORT_SYMBOL_GPL(generic_device_group);
  
+/*
+ * Generic device_group call-back function. It just allocates one
+ * iommu-group per iommu driver.
+ */
+struct iommu_group *generic_single_device_group(struct device *dev)
+{
+	struct iommu_device *iommu = dev->iommu->iommu_dev;
+
+	lockdep_assert_held(&dev_iommu_group_lock);
+
+	if (!iommu->singleton_group) {
+		struct iommu_group *group;
+
+		group = iommu_group_alloc();
+		if (IS_ERR(group))
+			return group;
+		iommu->singleton_group = group;
+	}
+	return iommu_group_ref_get(iommu->singleton_group);
+}
+EXPORT_SYMBOL_GPL(generic_single_device_group);

+
  /*
   * Use standard PCI bus topology, isolation features, and DMA alias quirks
   * to find or create an IOMMU group for a device.

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index b1dcb1b9b17040..f1e18e81fca78b 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h

@@ -361,6 +361,7 @@ struct iommu_domain_ops {
   * @list: Used by the iommu-core to keep a list of registered iommus
   * @ops: iommu-ops for talking to this iommu
   * @dev: struct device for sysfs handling
+ * @singleton_group: Used internally for drivers that have only one group
   * @max_pasids: number of supported PASIDs
   */
  struct iommu_device {

@@ -368,6 +369,7 @@ struct iommu_device {
  	const struct iommu_ops *ops;
  	struct fwnode_handle *fwnode;
  	struct device *dev;
+	struct iommu_group *singleton_group;
  	u32 max_pasids;
  };
  

@@ -640,6 +642,7 @@ extern struct iommu_group *pci_device_group(struct device *dev);
  extern struct iommu_group *generic_device_group(struct device *dev);
  /* FSL-MC device grouping function */
  struct iommu_group *fsl_mc_device_group(struct device *dev);
+extern struct iommu_group *generic_single_device_group(struct device *dev);