Re: [Qemu-devel] VFIO based vGPU(was Re: [Announcement] 2015-Q3 release of XenGT - a Mediated ...)

[Jike Song]

On 01/27/2016 09:34 AM, Yang Zhang wrote:
> On 2016/1/27 8:06, Jike Song wrote:
>> On 01/26/2016 10:05 PM, Yang Zhang wrote:
>>> On 2016/1/26 15:41, Jike Song wrote:
>>>
>>>> We will need to extend:
>>>>
>>>>    - VFIO_DEVICE_GET_REGION_INFO
>>>>
>>>>
>>>> a) adding a flag: DONT_MAP. For example, the MMIO of vgpu
>>>> should be trapped instead of being mmap-ed.
>>>
>>> I may not in the context, but i am curious how to handle the DONT_MAP in
>>> vfio driver? Since there are no real MMIO maps into the region and i
>>> suppose the access to the region should be handled by vgpu in i915
>>> driver, but currently most of the mmio accesses are handled by Qemu.
>>>
>>
>> Hi Yang,
>>
>> MMIO accesses are supposed to be handled in kernel, without vm-exiting
>> to QEMU, similar to in-kernel irqchip :)
> 
> The question is current vfio doesn't support it. The long discussion 
> between Alex and Kevin is what i am to understand how KVMGT works under 
> vfio framework.
>

Yes, good to expose it earlier.

Previously Kevin and I thought KVMGT is free to register an iodev,
responsible for a MMIO range r/w, to KVM hypervisor directly. If this is
not acceptable then we will have to figure out an alternative.

--
Thanks,
Jike