Re: [RFC PATCH] vfio: VFIO PCI driver for Qemu

[Andreas Hartmann <andihartmann@01019freenet.de>]

Avi Kivity schrieb:
> On 07/26/2012 12:28 PM, Andreas Hartmann wrote:
>> Avi Kivity wrote:
>>> On 07/25/2012 10:53 PM, Alex Williamson wrote:
>>>> On Wed, 2012-07-25 at 22:30 +0300, Avi Kivity wrote:
>>>>> On 07/25/2012 08:03 PM, Alex Williamson wrote:
>>>>>> This adds PCI based device assignment to Qemu using the Linux VFIO
>>>>>> userspace driver interface.  After setting up VFIO device access,
>>>>>> devices can be added to Qemu guests using the vfio-pci device
>>>>>> option:
>>>>>>
>>>>>>  -device vfio-pci,host=1:10.1,id=net0
>>>>>>
>>>>>>
>>>>>
>>>>> Let's use the same syntax as for kvm device assignment.  Then we can
>>>>> fall back on kvm when vfio is not available.  We can also have an
>>>>> optional parameter kernel-driver to explicitly select vfio or kvm.
>>>>
>>>> This seems confusing to me, pci-assign already has options like
>>>> prefer_msi, share_intx, and configfd that vfio doesn't.  I'm sure vfio
>>>> will eventually get options that pci-assign won't have.  How is a user
>>>> supposed to figure out what options are actually available from -device
>>>> pci-assign,? 
>>>
>>> Read the documentation.
>>>
>>>> Isn't this the same as asking to drop all model specific
>>>> devices and just use -device net,model=e1000... hey, we've been there
>>>> before ;)  Thanks,
>>>
>>> It's not.  e1000 is a guest visible feature. vfio and kvm assignment do
>>> exactly the same thing, as far as the guest is concerned,
>>
>> The big difference between vfio and old kvm assignment is: vfio does
>> work for PCI here, kvm doesn't!
> 
> Do we know why it doesn't work?
>
>> Please let the users decide them self which tool to use!
> 
> -device pci-assign,kernel-driver=vfio
> 
> (it will be the default in any case)

This would be ok from the perspective of an user. I'm happy with any
solution, which gives the user the ability to select the appropriate driver.


Kind regards,
Andreas