On Tue, 31 May 2016 10:29:10 +0800 Jike Song <jike.s...@intel.com> wrote:
> On 05/28/2016 10:56 PM, Alex Williamson wrote: > > On Fri, 27 May 2016 22:43:54 +0000 > > "Tian, Kevin" <kevin.t...@intel.com> 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. If it's part of running on a Xen platform and not trying to interact with a VM in ways that are out of scope for vfio, I might be open to it, I'd need to see a proposal. This also goes back to my question of how does vfio know whether it's configuring a device for a guest driver or a guest VM, with kvm these are one and the same. Thanks, Alex
