linux-kernel - Re: [PATCH] VFIO driver: Non-privileged user level PCI drivers

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Date:	Sun, 30 May 2010 17:53:09 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Tom Lyon <pugs@...co.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, chrisw@...s-sol.org, joro@...tes.org,
	hjk@...utronix.de, gregkh@...e.de, aafabbri@...co.com,
	scofeldm@...co.com
Subject: Re: [PATCH] VFIO driver: Non-privileged user level PCI drivers

On Sun, May 30, 2010 at 04:13:59PM +0300, Avi Kivity wrote:
> On 05/30/2010 04:03 PM, Michael S. Tsirkin wrote:
>>
>>    
>>>>>> IMO this was because this driver does two things: programming iommu and
>>>>>> handling interrupts. uio does interrupt handling.
>>>>>> We could have moved iommu / DMA programming to
>>>>>> a separate driver, and have uio work with it.
>>>>>> This would solve limitation of the current driver
>>>>>> that is needs an iommu domain per device.
>>>>>>
>>>>>>
>>>>>>            
>>>>> How do we enforce security then?  We need to ensure that unprivileged
>>>>> users can only use the device with an iommu.
>>>>>
>>>>>          
>>>> Force assigning to iommu before we allow any other operation?
>>>>
>>>>        
>>> That means the driver must be aware of the iommu.
>>>      
>> The userspace driver? Yes. And It is a good thing to be explicit
>> there anyway, since this lets userspace map a non-contigious
>> virtual address list into a contiguous bus address range.
>>    
>
> No, the kernel driver.  It cannot allow userspace to enable bus  
> mastering unless it knows the iommu is enabled for the device and remaps  
> dma to user pages.

So what I suggested is failing any kind of access until iommu
is assigned.

>
> -- 
> error compiling committee.c: too many arguments to function
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