The devices on platform/amba/fsl-mc/PCI buses could be bound to drivers
with the device DMA managed by kernel drivers or user-space applications.
Unfortunately, multiple devices may be placed in the same IOMMU group
because they cannot be isolated from each other. The DMA on these devices
must either be entirely under kernel control or userspace control, never
a mixture. Otherwise the driver integrity is not guaranteed because they
could access each other through the peer-to-peer accesses which by-pass
the IOMMU protection.
This checks and sets the default DMA mode during driver binding, and
cleanups during driver unbinding. In the default mode, the device DMA is
managed by the device driver which handles DMA operations through the
kernel DMA APIs (see Documentation/core-api/dma-api.rst).
For cases where the devices are assigned for userspace control through the
userspace driver framework(i.e. VFIO), the drivers(for example, vfio_pci/
vfio_platfrom etc.) may set a new flag (driver_managed_dma) to skip this
default setting in the assumption that the drivers know what they are
doing with the device DMA.
With the IOMMU layer knowing DMA ownership of each device, above problem
can be solved.
Cc: Greg Kroah-Hartman
Cc: Bjorn Helgaas
Cc: Stuart Yoder
Cc: Laurentiu Tudor
Signed-off-by: Lu Baolu
---
include/linux/amba/bus.h| 8
include/linux/fsl/mc.h | 8
include/linux/pci.h | 8
include/linux/platform_device.h | 8
drivers/amba/bus.c | 20
drivers/base/platform.c | 20
drivers/bus/fsl-mc/fsl-mc-bus.c | 26 --
drivers/pci/pci-driver.c| 21 +
8 files changed, 117 insertions(+), 2 deletions(-)
diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h
index 6c7f47846971..e9cd981be94e 100644
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h
@@ -79,6 +79,14 @@ struct amba_driver {
void(*remove)(struct amba_device *);
void(*shutdown)(struct amba_device *);
const struct amba_id*id_table;
+ /*
+* For most device drivers, no need to care about this flag as long as
+* all DMAs are handled through the kernel DMA API. For some special
+* ones, for example VFIO drivers, they know how to manage the DMA
+* themselves and set this flag so that the IOMMU layer will allow them
+* to setup and manage their own I/O address space.
+*/
+ bool driver_managed_dma;
};
/*
diff --git a/include/linux/fsl/mc.h b/include/linux/fsl/mc.h
index 7b6c42bfb660..27efef8affb1 100644
--- a/include/linux/fsl/mc.h
+++ b/include/linux/fsl/mc.h
@@ -32,6 +32,13 @@ struct fsl_mc_io;
* @shutdown: Function called at shutdown time to quiesce the device
* @suspend: Function called when a device is stopped
* @resume: Function called when a device is resumed
+ * @driver_managed_dma: Device driver doesn't use kernel DMA API for DMA.
+ * For most device drivers, no need to care about this flag
+ * as long as all DMAs are handled through the kernel DMA API.
+ * For some special ones, for example VFIO drivers, they know
+ * how to manage the DMA themselves and set this flag so that
+ * the IOMMU layer will allow them to setup and manage their
+ * own I/O address space.
*
* Generic DPAA device driver object for device drivers that are registered
* with a DPRC bus. This structure is to be embedded in each device-specific
@@ -45,6 +52,7 @@ struct fsl_mc_driver {
void (*shutdown)(struct fsl_mc_device *dev);
int (*suspend)(struct fsl_mc_device *dev, pm_message_t state);
int (*resume)(struct fsl_mc_device *dev);
+ bool driver_managed_dma;
};
#define to_fsl_mc_driver(_drv) \
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 8253a5413d7c..b94bce839b83 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -894,6 +894,13 @@ struct module;
* created once it is bound to the driver.
* @driver:Driver model structure.
* @dynids:List of dynamically added device IDs.
+ * @driver_managed_dma: Device driver doesn't use kernel DMA API for DMA.
+ * For most device drivers, no need to care about this flag
+ * as long as all DMAs are handled through the kernel DMA API.
+ * For some special ones, for example VFIO drivers, they know
+ * how to manage the DMA themselves and set this flag so that
+ * the IOMMU layer will allow them to setup and manage their
+ * own I/O address space.
*/
struct pci_driver {
struct list_headnode;
@@ -912,6 +919,7 @@ struct pci_driver {
const struct attribute_group **dev_groups;
struct device_driverdriver;
struct pci_dynids dynids;
+
