Re: [PATCH v3 10/16] iommu: introduce device fault report API

Jean-Philippe Brucker
2018-01-18T19:24:52Z

Hi Jacob,

I've got minor comments after working with this patch, sorry for the
multiple replies

On 17/11/17 18:55, Jacob Pan wrote:
[...]
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 829e9e9..97b7990 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group *group, struct device *dev)
> goto err_free_name;
> }
>
> + dev->iommu_param = kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);

This should be "sizeof(struct iommu_param)" or maybe
"sizeof(*dev->iommu_param)".

> + if (!dev->iommu_param) {
> + ret = -ENOMEM;
> + goto err_free_name;
> + }
> +
> kobject_get(group->devices_kobj);
>
> dev->iommu_group = group;
> @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device *dev)
> sysfs_remove_link(&dev->kobj, "iommu_group");
>
> trace_remove_device_from_group(group->id, dev);
> -
> + kfree(dev->iommu_param);
> kfree(device->name);
> kfree(device);
> dev->iommu_group = NULL;
> @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct iommu_group *group,
> }
> EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
>
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + /*
> + * Device iommu_param should have been allocated when device is
> + * added to its iommu_group.
> + */
> + if (!idata)
> + return -EINVAL;
> + /* Only allow one fault handler registered for each device */
> + if (idata->fault_param)
> + return -EBUSY;
> + get_device(dev);
> + idata->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);
> + if (!idata->fault_param)
> + return -ENOMEM;
> + idata->fault_param->handler = handler;
> + idata->fault_param->data = data;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + if (!idata)
> + return -EINVAL;
> +
> + kfree(idata->fault_param);
> + idata->fault_param = NULL;
> + put_device(dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);

We should probably document register() and unregister() functions since
they are part of the device driver API. If it helps I came up with:

/**
* iommu_register_device_fault_handler() - Register a device fault handler
* @dev: the device
* @handler: the fault handler
* @data: private data passed as argument to the handler
*
* When an IOMMU fault event is received, call this handler with the fault event
* and data as argument. The handler should return 0. If the fault is
* recoverable (IOMMU_FAULT_PAGE_REQ), the handler must also complete
* the fault by calling iommu_page_response() with one of the following
* response code:
* - IOMMU_PAGE_RESP_SUCCESS: retry the translation
* - IOMMU_PAGE_RESP_INVALID: terminate the fault
* - IOMMU_PAGE_RESP_FAILURE: terminate the fault and stop reporting
* page faults if possible.
*
* Return 0 if the fault handler was installed successfully, or an error.
*/

/**
* iommu_unregister_device_fault_handler() - Unregister the device fault handler
* @dev: the device
*
* Remove the device fault handler installed with
* iommu_register_device_fault_handler().
*
* Return 0 on success, or an error.
*/

Thanks,
Jean