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driver core: Add dma_cleanup callback in bus_type

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The bus_type structure defines dma_configure() callback for bus drivers
to configure DMA on the devices. This adds the paired dma_cleanup()
callback and calls it during driver unbinding so that bus drivers can do
some cleanup work.

One use case for this paired DMA callbacks is for the bus driver to check
for DMA ownership conflicts during driver binding, where multiple devices
belonging to a same IOMMU group (the minimum granularity of isolation and
protection) may be assigned to kernel drivers or user space respectively.

Without this change, for example, the vfio driver has to listen to a bus
BOUND_DRIVER event and then BUG_ON() in case of dma ownership conflict.
This leads to bad user experience since careless driver binding operation
may crash the system if the admin overlooks the group restriction. Aside
from bad design, this leads to a security problem as a root user, even with
lockdown=integrity, can force the kernel to BUG.

With this change, the bus driver could check and set the DMA ownership in
driver binding process and fail on ownership conflicts. The DMA ownership
should be released during driver unbinding.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20220418005000.897664-3-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Lu Baolu 2022-04-18 08:49:51 +08:00 committed by Joerg Roedel
parent 1ea2a07a53
commit 25f3bcfc54
2 changed files with 8 additions and 0 deletions
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5
drivers/base/dd.c
View File

@ -671,6 +671,8 @@ sysfs_failed:
if (dev->bus)
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
if (dev->bus && dev->bus->dma_cleanup)
dev->bus->dma_cleanup(dev);
pinctrl_bind_failed:
device_links_no_driver(dev);
device_unbind_cleanup(dev);
@ -1199,6 +1201,9 @@ static void __device_release_driver(struct device *dev, struct device *parent)
device_remove(dev);
if (dev->bus && dev->bus->dma_cleanup)
dev->bus->dma_cleanup(dev);
device_links_driver_cleanup(dev);
device_unbind_cleanup(dev);

3
include/linux/device/bus.h
View File

@ -59,6 +59,8 @@ struct fwnode_handle;
* bus supports.
* @dma_configure: Called to setup DMA configuration on a device on
* this bus.
* @dma_cleanup: Called to cleanup DMA configuration on a device on
* this bus.
* @pm: Power management operations of this bus, callback the specific
* device driver's pm-ops.
* @iommu_ops: IOMMU specific operations for this bus, used to attach IOMMU
@ -103,6 +105,7 @@ struct bus_type {
int (*num_vf)(struct device *dev);
int (*dma_configure)(struct device *dev);
void (*dma_cleanup)(struct device *dev);
const struct dev_pm_ops *pm;