[PATCH v5 07/14] PCI: Add driver dma ownership management

[Lu Baolu]

Multiple PCI devices may be placed in the same IOMMU group because
they cannot be isolated from each other. These devices must either be
entirely under kernel control or userspace control, never a mixture. This
checks and sets DMA ownership during driver binding, and release the
ownership during driver unbinding.

The device driver may set a new flag (no_kernel_api_dma) to skip calling
iommu_device_use_dma_api() during the binding process. For instance, the
userspace framework drivers (vfio etc.) which need to manually claim
their own dma ownership when assigning the device to userspace.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/linux/pci.h      |  5 +++++
 drivers/pci/pci-driver.c | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 18a75c8e615c..d29a990e3f02 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -882,6 +882,10 @@ struct module;
  *              created once it is bound to the driver.
  * @driver:	Driver model structure.
  * @dynids:	List of dynamically added device IDs.
+ * @no_kernel_api_dma: Device driver doesn't use kernel DMA API for DMA.
+ *		Drivers which don't require DMA or want to manually claim the
+ *		owner type (e.g. userspace driver frameworks) could set this
+ *		flag.
  */
 struct pci_driver {
 	struct list_head	node;
@@ -900,6 +904,7 @@ struct pci_driver {
 	const struct attribute_group **dev_groups;
 	struct device_driver	driver;
 	struct pci_dynids	dynids;
+	bool no_kernel_api_dma;
 };
 
 static inline struct pci_driver *to_pci_driver(struct device_driver *drv)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 588588cfda48..4e003ea12718 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -20,6 +20,7 @@
 #include <linux/of_device.h>
 #include <linux/acpi.h>
 #include <linux/dma-map-ops.h>
+#include <linux/iommu.h>
 #include "pci.h"
 #include "pcie/portdrv.h"
 
@@ -1590,9 +1591,16 @@ static int pci_bus_num_vf(struct device *dev)
  */
 static int pci_dma_configure(struct device *dev)
 {
+	struct pci_driver *driver = to_pci_driver(dev->driver);
 	struct device *bridge;
 	int ret = 0;
 
+	if (!driver->no_kernel_api_dma) {
+		ret = iommu_device_use_dma_api(dev);
+		if (ret)
+			return ret;
+	}
+
 	bridge = pci_get_host_bridge_device(to_pci_dev(dev));
 
 	if (IS_ENABLED(CONFIG_OF) && bridge->parent &&
@@ -1605,9 +1613,21 @@ static int pci_dma_configure(struct device *dev)
 	}
 
 	pci_put_host_bridge_device(bridge);
+
+	if (ret && !driver->no_kernel_api_dma)
+		iommu_device_unuse_dma_api(dev);
+
 	return ret;
 }
 
+static void pci_dma_cleanup(struct device *dev)
+{
+	struct pci_driver *driver = to_pci_driver(dev->driver);
+
+	if (!driver->no_kernel_api_dma)
+		iommu_device_unuse_dma_api(dev);
+}
+
 struct bus_type pci_bus_type = {
 	.name		= "pci",
 	.match		= pci_bus_match,
@@ -1621,6 +1641,7 @@ struct bus_type pci_bus_type = {
 	.pm		= PCI_PM_OPS_PTR,
 	.num_vf		= pci_bus_num_vf,
 	.dma_configure	= pci_dma_configure,
+	.dma_cleanup	= pci_dma_cleanup,
 };
 EXPORT_SYMBOL(pci_bus_type);
 
-- 
2.25.1