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

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Date:   Mon, 23 Apr 2018 12:30:13 +0100
From:   Jean-Philippe Brucker <Jean-Philippe.Brucker@....com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Jean Delvare <khali@...ux-fr.org>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: Re: [PATCH v4 12/22] iommu: introduce device fault report API

On Mon, Apr 16, 2018 at 10:49:01PM +0100, 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;
> +
> +	mutex_lock(&param->lock);
> +	get_device(dev);
> +	param->fault_param =
> +		kzalloc(sizeof(struct iommu_fault_param), GFP_ATOMIC);

This can be GFP_KERNEL

[...]
> +int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
> +{
> +	int ret = 0;
> +	struct iommu_fault_event *evt_pending;
> +	struct iommu_fault_param *fparam;
> +
> +	/* iommu_param is allocated when device is added to group */
> +	if (!dev->iommu_param | !evt)
> +		return -EINVAL;
> +	/* we only report device fault if there is a handler registered */
> +	mutex_lock(&dev->iommu_param->lock);
> +	if (!dev->iommu_param->fault_param ||
> +		!dev->iommu_param->fault_param->handler) {
> +		ret = -EINVAL;
> +		goto done_unlock;
> +	}
> +	fparam = dev->iommu_param->fault_param;
> +	if (evt->type == IOMMU_FAULT_PAGE_REQ && evt->last_req) {
> +		evt_pending = kzalloc(sizeof(*evt_pending), GFP_ATOMIC);

We're expecting caller to be a thread at the moment, so this could be
GFP_KERNEL too. You could also use kmemdup to remove the memcpy below

[...]
> +static inline int iommu_register_device_fault_handler(struct device *dev,
> +						iommu_dev_fault_handler_t handler,
> +						void *data)
> +{
> +	return 0;

Should return -ENODEV

Thanks,
Jean