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

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Message-ID: <20180430115456.54a4b22e@jacob-builder>
Date:   Mon, 30 Apr 2018 11:54:56 -0700
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>,
        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>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v4 12/22] iommu: introduce device fault report API

On Mon, 30 Apr 2018 17:53:52 +0100
Jean-Philippe Brucker <jean-philippe.brucker@....com> wrote:

> 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
agreed, same as corrections below. Thanks!
> 
>  [...]  
> 
> 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

[Jacob Pan]