Re: [Qemu-devel] [PATCH v7 0/4] Add Mediated device support

[Kirti Wankhede]

On 9/8/2016 3:43 AM, Alex Williamson wrote:
> On Wed, 7 Sep 2016 23:36:28 +0530
> Kirti Wankhede <address@hidden> wrote:
> 
>> On 9/7/2016 10:14 PM, Alex Williamson wrote:
>>> On Wed, 7 Sep 2016 21:45:31 +0530
>>> Kirti Wankhede <address@hidden> wrote:
>>>   
>>>> On 9/7/2016 2:58 AM, Alex Williamson wrote:  
>>>>> On Wed, 7 Sep 2016 01:05:11 +0530
>>>>> Kirti Wankhede <address@hidden> wrote:
>>>>>     
>>>>>> On 9/6/2016 11:10 PM, Alex Williamson wrote:    
>>>>>>> On Sat, 3 Sep 2016 22:04:56 +0530
>>>>>>> Kirti Wankhede <address@hidden> wrote:
>>>>>>>       
>>>>>>>> On 9/3/2016 3:18 AM, Paolo Bonzini wrote:      
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 02/09/2016 20:33, Kirti Wankhede wrote:        

...

> 
> Philosophically, mdev devices should be entirely independent of one
> another.  A user can set the same iommu context for multiple mdevs
> by placing them in the same container.  A user should be able to
> stop using an mdev in one place and start using it somewhere else.
> It should be a fungible $TYPE device.  It's an NVIDIA-only requirement
> that imposes this association of mdev devices into groups and I don't
> particularly see it as beneficial to the mdev architecture.  So why
> make it a standard part of the interface?
> 

Yes, I agree. This might not be each vendor's requirement.


> We could do keying at the layer you suggest, assuming we can find
> something that doesn't restrict the user, but we could make that
> optional.  

We can key on 'container'. Devices should be in same VFIO 'container'.
open() call should fail if they are found to be in different containers.

> For instance, say we did key on pid, there could be an
> attribute in the supported types hierarchy to indicate this type
> supports(requires) pid-sets.  Each mdev device with this attribute
> would create a pid-group file in sysfs where libvirt could associate
> the device.  Only for those mdev devices requiring it.
> 

We are OK with this suggestion if this works of libvirt integration.
We can have file in types directory in supported types as 'requires_group'.

Thanks,
Kirti

> The alternative is that we need to find some mechanism for this
> association that doesn't impose arbitrary requirements, and potentially
> usage restrictions on vendors that don't have this need.  Thanks,
> 
> Alex
>