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

[Avi Kivity <avi@redhat.com>]

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.


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