Re: [RFC v2] /dev/iommu uAPI proposal

Jason Gunthorpe
2021-07-13T23:22:51Z

On Tue, Jul 13, 2021 at 11:20:12PM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Wednesday, July 14, 2021 7:03 AM
> >
> > On Tue, Jul 13, 2021 at 10:48:38PM +0000, Tian, Kevin wrote:
> >
> > > We can still bind to the parent with cookie, but with
> > > iommu_register_ sw_device() IOMMU fd knows that this binding doesn't
> > > need to establish any security context via IOMMU API.
> >
> > AFAIK there is no reason to involve the parent PCI or other device in
> > SW mode. The iommufd doesn't need to be aware of anything there.
> >
>
> Yes. but does it makes sense to have an unified model in IOMMU fd
> which always have a [struct device, cookie] with flags to indicate whether
> the binding/attaching should be specially handled for sw mdev? Or
> are you suggesting that lacking of struct device is actually the indicator
> for such trick?

I think you've veered into such micro implementation details that it
is better to wait and see how things look.

The important point here is that whatever physical device is under a
SW mdev does not need to be passed to the iommufd because there is
nothing it can do with that information.

Jason