linux-kernel - Re: [PATCH v2 08/16] iommu: introduce device fault data

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Date:   Mon, 13 Nov 2017 17:23:14 +0000
From:   Jean-Philippe Brucker <jean-philippe.brucker@....com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     "Liu, Yi L" <yi.l.liu@...el.com>,
        "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>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "Lan, Tianyu" <tianyu.lan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [PATCH v2 08/16] iommu: introduce device fault data

On 13/11/17 16:57, Jacob Pan wrote:
> On Mon, 13 Nov 2017 13:06:24 +0000
> Jean-Philippe Brucker <jean-philippe.brucker@....com> wrote:
> 
>> On 10/11/17 22:18, Jacob Pan wrote:
>>> On Fri, 10 Nov 2017 13:54:59 +0000
>>> Jean-Philippe Brucker <jean-philippe.brucker@....com> wrote:
>>>   
>>>> On 09/11/17 19:36, Jacob Pan wrote:  
>>>>> On Tue, 7 Nov 2017 11:38:50 +0000
>>>>> Jean-Philippe Brucker <jean-philippe.brucker@....com> wrote:
>>>>>     
>>>>>> I think the IOMMU should pass the struct device associated to the
>>>>>> BDF to the fault handler. The fault handler can then deduce the
>>>>>> BDF from struct device if it needs to. This also allows to
>>>>>> support faults from non-PCI devices, where the BDF or deviceID
>>>>>> is specific to the IOMMU and doesn't mean anything to the device
>>>>>> driver. 
>>>>> Passing struct device is only useful if we use shared fault
>>>>> notification method, as I did in V1 patch with group level or
>>>>> current domain level.
>>>>>
>>>>> But the patch proposed here is a per device callback, there is no
>>>>> need for passing struct device since it is implied.    
>>>>
>>>> Sorry I had lost sight of the original patch in this thread. I
>>>> think the callback is fine as it is, in your patch:
>>>>
>>>> typedef int (*iommu_dev_fault_handler_t)(struct device *, struct
>>>> iommu_fault_event *);
>>>>  
>>> I should have removed struct device here also. thanks for pointing
>>> it out.  
>>
>> Why remove it? The device driver will use a single C function as fault
>> handler for multiple devices, so it needs struct device argument to
>> understand the context.
>>
> I meant to replace struct device * with just a void *, driver can
> register fault callback with instance of their private data, this could
> be a container struct of struct device.
> e.g.
> int iommu_register_device_fault_handler(struct device *dev,
> 				iommu_dev_fault_handler_t handler, void
> 				*data);
> 
> typedef int (*iommu_dev_fault_handler_t)(struct iommu_fault_event *, void *);

Ah I see. Yes that should work

Thanks,
Jean