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

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Message-ID: <20100530130332.GM27611@redhat.com>
Date:	Sun, 30 May 2010 16:03:32 +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 04:01:53PM +0300, Avi Kivity wrote:
> On 05/30/2010 03:49 PM, Michael S. Tsirkin wrote:
>> On Sun, May 30, 2010 at 03:27:05PM +0300, Avi Kivity wrote:
>>    
>>> On 05/30/2010 03:19 PM, Michael S. Tsirkin wrote:
>>>      
>>>> On Fri, May 28, 2010 at 04:07:38PM -0700, Tom Lyon wrote:
>>>>
>>>>        
>>>>> The VFIO "driver" is used to allow privileged AND non-privileged processes to
>>>>> implement user-level device drivers for any well-behaved PCI, PCI-X, and PCIe
>>>>> devices.
>>>>> 	Signed-off-by: Tom Lyon<pugs@...co.com>
>>>>> ---
>>>>> This patch is the evolution of code which was first proposed as a patch to
>>>>> uio/uio_pci_generic, then as a more generic uio patch. Now it is taken entirely
>>>>> out of the uio framework, and things seem much cleaner. Of course, there is
>>>>> a lot of functional overlap with uio, but the previous version just seemed
>>>>> like a giant mode switch in the uio code that did not lead to clarity for
>>>>> either the new or old code.
>>>>>
>>>>>          
>>>> 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.

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