@@ -264,6 +264,7 @@ int iommu_device_register(struct iommu_device *iommu,
return -EBUSY;
iommu->ops = ops;
+ iommu->hwdev = hwdev;
if (hwdev)
iommu->fwnode = dev_fwnode(hwdev);
@@ -1802,9 +1803,18 @@ static int probe_iommu_group(struct device *dev, void *data)
struct probe_iommu_args *args = data;
int ret;
+ /*
+ * The iommu device itself is not probed, in part because no sane iommu
+ * should self-attach to its own HW, but specifically because we already
+ * hold the device_lock for the hwdev when calling here.
+ */
+ if (args->iommu->hwdev == dev)
+ return 0;
+
device_lock(dev);
ret = __iommu_probe_device(dev, args->group_list);
device_unlock(dev);
+
if (ret == -ENODEV)
ret = 0;
@@ -1241,6 +1241,7 @@ static int omap_iommu_probe(struct platform_device *pdev)
* an iommu without registering it, so re-run probe again to try
* to match any devices that are waiting for this iommu.
*/
+ obj->iommu.hwdev = &pdev->dev;
bus_iommu_probe(&platform_bus_type, &obj->iommu);
}
@@ -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
+ * @hwdev: The device HW that controls the iommu
* @singleton_group: Used internally for drivers that have only one group
* @max_pasids: number of supported PASIDs
*/
@@ -369,6 +370,7 @@ struct iommu_device {
const struct iommu_ops *ops;
struct fwnode_handle *fwnode;
struct device *dev;
+ struct device *hwdev;
struct iommu_group *singleton_group;
u32 max_pasids;
};
When bus_iommu_probe() runs it can attempt to probe the iommu itself, for instance if the iommu is located on a platform_bus. This will cause the device_lock() to deadlock on itself as the device_driver probe() callback for the device calling iommu_device_register() already holds the device_lock(): probe_iommu_group+0x18/0x38 bus_for_each_dev+0xe4/0x168 bus_iommu_probe+0x8c/0x240 iommu_device_register+0x120/0x1b0 mtk_iommu_probe+0x494/0x7a0 platform_probe+0x94/0x100 really_probe+0x1e4/0x3e8 __driver_probe_device+0xc0/0x1a0 driver_probe_device+0x110/0x1f0 __device_attach_driver+0xf0/0x1b0 bus_for_each_drv+0xf0/0x170 __device_attach+0x120/0x240 device_initial_probe+0x1c/0x30 bus_probe_device+0xdc/0xe8 deferred_probe_work_func+0xf0/0x140 process_one_work+0x3b0/0x910 worker_thread+0x33c/0x610 kthread+0x1dc/0x1f0 ret_from_fork+0x10/0x20 Keep track of the iommu itself and do not attempt to relock the device while doing the probe_iommu_group scan. To accommodate omap's use of unregistered struct iommu_device's add a new 'hwdev' member to keep track of the hwdev in all cases. Normally this would be dev->parent, but since omap doesn't allocate that struct it won't exist for it. Fixes: a16b5d1681ab ("iommu: Complete the locking for dev->iommu_group") Reported-by: Chen-Yu Tsai <wenst@chromium.org> Closes: https://lore.kernel.org/linux-iommu/CAGXv+5E-f9AteAYkmXYzVDZFSA_royc7-bS5LcrzzuHDnXccwA@mail.gmail.com Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Tested-by: Chen-Yu Tsai <wenst@chromium.org> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> --- drivers/iommu/iommu.c | 10 ++++++++++ drivers/iommu/omap-iommu.c | 1 + include/linux/iommu.h | 2 ++ 3 files changed, 13 insertions(+)