RE: [RFC PATCH 12/21] KVM: IOMMUFD: MEMFD: Map private pages

Tian, Kevin
2024-09-05T08:29:33Z

> From: Williams, Dan J <dan.j.williams@intel.com>
> Sent: Wednesday, September 4, 2024 9:00 AM
>
> Jason Gunthorpe wrote:
> > On Tue, Sep 03, 2024 at 01:34:29PM -0700, Dan Williams wrote:
> > > Jason Gunthorpe wrote:
> > > > On Fri, Aug 30, 2024 at 01:20:12PM +0800, Xu Yilun wrote:
> > > >
> > > > > > If that is true for the confidential compute, I don't know.
> > > > >
> > > > > For Intel TDX TEE-IO, there may be a different story.
> > > > >
> > > > > Architechturely the secure IOMMU page table has to share with KVM
> secure
> > > > > stage 2 (SEPT). The SEPT is managed by firmware (TDX Module), TDX
> Module
> > > > > ensures the SEPT operations good for secure IOMMU, so there is no
> much
> > > > > trick to play for SEPT.
> > > >
> > > > Yes, I think ARM will do the same as well.
> > > >
> > > > From a uAPI perspective we need some way to create a secure vPCI
> > > > function linked to a KVM and some IOMMUs will implicitly get a
> > > > translation from the secure world and some IOMMUs will need to
> manage
> > > > it in untrusted hypervisor memory.
> > >
> > > Yes. This matches the line of though I had for the PCI TSM core
> > > interface.
> >
> > Okay, but I don't think you should ever be binding any PCI stuff to
> > KVM without involving VFIO in some way.
> >
> > VFIO is the security proof that userspace is even permitted to touch
> > that PCI Device at all.
>
> Right, I think VFIO grows a uAPI to make a vPCI device "bind capable"
> which ties together the PCI/TSM security context, the assignable device
> context and the KVM context.
>

Could you elaborate why the new uAPI is for making vPCI "bind capable"
instead of doing the actual binding to KVM?