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SubjectRe: [PATCH v4 12/22] iommu: introduce device fault report API
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Hi,

I noticed a couple issues when testing

On 16/04/18 22:49, Jacob Pan wrote:
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *param = dev->iommu_param;
> +
> + /*
> + * Device iommu_param should have been allocated when device is
> + * added to its iommu_group.
> + */
> + if (!param)
> + return -EINVAL;
> +
> + /* Only allow one fault handler registered for each device */
> + if (param->fault_param)
> + return -EBUSY;

Should this be inside the param lock? We probably don't expect
concurrent register/unregister but it seems cleaner

> +
> + mutex_lock(&param->lock);
> + get_device(dev);
> + param->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_ATOMIC);
> + if (!param->fault_param) {
> + put_device(dev);
> + mutex_unlock(&param->lock);
> + return -ENOMEM;
> + }
> + mutex_init(&param->fault_param->lock);
> + param->fault_param->handler = handler;
> + param->fault_param->data = data;
> + INIT_LIST_HEAD(&param->fault_param->faults);
> +
> + mutex_unlock(&param->lock);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +/**
> + * 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.
> + */
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *param = dev->iommu_param;
> + int ret = 0;
> +
> + if (!param)
> + return -EINVAL;
> +
> + mutex_lock(&param->lock);

We should return EINVAL here, if fault_param is NULL. That way users can
call unregister_fault_handler unconditionally in their cleanup paths

> + /* we cannot unregister handler if there are pending faults */
> + if (list_empty(&param->fault_param->faults)) {

if (!list_empty(...))

> + ret = -EBUSY;
> + goto unlock;
> + }
> +
> + list_del(&param->fault_param->faults);

faults is the list head, no need for list_del

> + kfree(param->fault_param);
> + param->fault_param = NULL;
> + put_device(dev);
> +
> +unlock:
> + mutex_unlock(&param->lock);
> +
> + return 0;

return ret

Thanks,
Jean

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