Re: [Qemu-devel] [RFC PATCH v4 0/3] Add Mediated device support[was: Add vGPU support]

[Jike Song]

On 05/28/2016 10:56 PM, Alex Williamson wrote:
> On Fri, 27 May 2016 22:43:54 +0000
> "Tian, Kevin" <address@hidden> wrote:
> 
>>
>> My impression was that you don't like hypervisor specific thing in VFIO,
>> which makes it a bit tricky to accomplish those tasks in kernel. If we 
>> can add Xen specific logic directly in VFIO (like vfio-iommu-xen you 
>> mentioned), the whole thing would be easier.
> 
> If vfio is hosted in dom0, then Xen is the platform and we need to
> interact with the hypervisor to manage the iommu.  That said, there are
> aspects of vfio that do not seem to map well to a hypervisor managed
> iommu or a Xen-like hypervisor.  For instance, how does dom0 manage
> iommu groups and what's the distinction of using vfio to manage a
> userspace driver in dom0 versus managing a device for another domain.
> In the case of kvm, vfio has no dependency on kvm, there is some minor
> interaction, but we're not running on kvm and it's not appropriate to
> use vfio as a gateway to interact with a hypervisor that may or may not
> exist.  Thanks,

Hi Alex,

Beyond iommu, there are other aspects vfio need to interact with Xen?
e.g. to pass-through MMIO, one have to call hypercalls to establish EPT
mappings.


--
Thanks,
Jike