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

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Message-ID: <4C026497.8070901@redhat.com>
Date:	Sun, 30 May 2010 16:13:59 +0300
From:	Avi Kivity <avi@...hat.com>
To:	"Michael S. Tsirkin" <mst@...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 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.


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

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