Re: [PATCH v4 12/22] iommu: introduce device fault report API

[Jean-Philippe Brucker]

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