Re: [Qemu-devel] [RFC v2] libvirt vGPU QEMU integration

[Tian, Kevin]

> From: Kirti Wankhede [mailto:address@hidden
> Sent: Wednesday, September 21, 2016 12:23 AM
> 
> 
> On 9/20/2016 8:13 PM, Alex Williamson wrote:
> > On Tue, 20 Sep 2016 19:51:58 +0530
> > Kirti Wankhede <address@hidden> wrote:
> >
> >> On 9/20/2016 3:06 AM, Alex Williamson wrote:
> >>> On Tue, 20 Sep 2016 02:05:52 +0530
> >>> Kirti Wankhede <address@hidden> wrote:
> >>>
> >>>> Hi libvirt experts,
> >>>>
> >>>>
> >>>> 'create':
> >>>>     Write-only file. Mandatory.
> >>>>     Accepts string to create mediated device.
> >>>>
> >>>> 'name':
> >>>>     Read-Only file. Mandatory.
> >>>>     Returns string, the name of that type id.
> >>>>
> >>>> 'fb_length':
> >>>>     Read-only file. Mandatory.
> >>>>     Returns <number>{K,M,G}, size of framebuffer.
> >>>
> >>> This can't be mandatory, it's only relevant to vGPU devices, vGPUs are
> >>> just one user of mediated devices.
> >>>
> >>
> >> As per our discussion in BOF, we would define class and its attributes.
> >> As I mentioned above these are attributes of "display" class.
> >
> > Just as I didn't know here, how does libvirt know the class of a given
> > type id?
> >
> 
> Yes, we need some way to identify the class as Daniel mentioned in his
> suggestion. Add a file 'class' in mdev_supported_types that would return
> the class.
> 
> 

'display' class or 'gpu' class? display represents only part of GPU 
functionalities. I assume you want to provide an unique class ID
for each type, instead of allowing multiple classes each identifying
a subset of controllable GPU resources (e.g. 'display', 'render', etc.)...

for unique class ID, I once considered whether it could be directly
inherited from class of parent device, since typically a vendor driver
creates mdev devices using the same type as physical device. But later
I realized one potential value of keep a class field for mdev types,
e.g. if we want to extend mdev to FPGA which could be programmed
as different classes of functionalities. :-)

Thanks
Kevin