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

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Date:   Tue, 23 Jan 2018 12:01:38 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....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>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Lan Tianyu <tianyu.lan@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v3 10/16] iommu: introduce device fault report API

On Thu, 18 Jan 2018 19:24:52 +0000
Jean-Philippe Brucker <jean-philippe.brucker@....com> wrote:

> 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)".
> 
good catch, thanks,
> > +	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.
>  */
> 
agreed. thanks. sorry about the delay.
> Thanks,
> Jean

[Jacob Pan]