[PATCH v3 07/18] PCI: Add driver dma ownership management

Lu Baolu
2021-12-06T02:00:23Z

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 vice versa, release the
ownership during driver unbinding.

Driver may set a new flag (suppress_auto_claim_dma_owner) to disable auto
claiming DMA_OWNER_DMA_API ownership in the binding process. For instance,
the userspace framework drivers (vfio etc.) which need to manually claim
DMA_OWNER_PRIVATE_DOMAIN_USER when assigning a device to userspace.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
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..1b29af0ab43b 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.
+ * @suppress_auto_claim_dma_owner: Disable auto claiming of kernel DMA owner.
+ * 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 suppress_auto_claim_dma_owner;
};

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..92712645e179 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->suppress_auto_claim_dma_owner) {
+ ret = iommu_device_set_dma_owner(dev, DMA_OWNER_DMA_API, NULL);
+ 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->suppress_auto_claim_dma_owner)
+ iommu_device_release_dma_owner(dev, DMA_OWNER_DMA_API);
+
return ret;
}

+static void pci_dma_cleanup(struct device *dev)
+{
+ struct pci_driver *driver = to_pci_driver(dev->driver);
+
+ if (!driver->suppress_auto_claim_dma_owner)
+ iommu_device_release_dma_owner(dev, DMA_OWNER_DMA_API);
+}
+
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