Re: [Qemu-devel] [RFC PATCH v3 3/3] VFIO Type1 IOMMU change: to support with iommu and without iommu

[Jike Song]

On 05/03/2016 02:40 AM, Kirti Wankhede wrote:
> VFIO Type1 IOMMU driver is designed for the devices which are IOMMU capable.
> vGPU device are only using IOMMU TYPE1 API, the underlying hardware can be
> managed by an IOMMU domain. To use most of the code of IOMMU driver for vGPU
> devices, type1 IOMMU driver is modified to support vGPU devices. This change
> exports functions to pin and unpin pages for vGPU devices.
> It maintains data of pinned pages for vGPU domain. This data is used to verify
> unpinning request and also used to unpin pages from detach_group().
> 
> Tested by assigning below combinations of devices to a single VM:
> - GPU pass through only
> - vGPU device only
> - One GPU pass through and one vGPU device
> - two GPU pass through

{the patch trimmed}

Hi Kirti,

 I have a question: in the scenario above, how many PCI BDFs do your vGPUs 
consume?

 Per my understanding, you take the GPA of a KVM guest as the IOVA of IOMMU 
domain,
and if there are multiple guests with vGPU assigned, the vGPUs must belong to
different vGPUs (thereby having different BDFs).

 Do I miss anything?


--
Thanks,
Jike