Re: [RFC PATCH 3/3] iommufd/tsm: Add tsm_bind/unbind iommufd ioctls

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Jun 04, 2025 at 01:31:38PM +0800, Xu Yilun wrote:
> On Tue, Jun 03, 2025 at 09:14:56AM -0300, Jason Gunthorpe wrote:
> > On Tue, Jun 03, 2025 at 06:50:13PM +0800, Xu Yilun wrote:
> > 
> > > I see. But I'm not sure if it can be a better story than ioctl(VFIO_TSM_BIND).
> > > You want VFIO unaware of TSM bind, e.g. try to hide pci_request/release_region(),
> > > but make VFIO aware of TSM unbind, which seems odd ...
> > 
> > request_region does not need to be done dynamically. It should be done
> > once when the VFIO cdev is opened. If you need some new ioctl to put
> > VFIO in a CC compatible mode then it should do all this stuff once. It
> > doesn't need to be dynamic.
> 
> But the unbind needs to be dynamic.

That has nothing to do with request_region.

> > I think all you want is to trigger VFIO to invalidate its MMIOs when
> > bind/unbind happens.
>
> Trigger VFIO to passively invalidate MMIOs during unbind is a TDX
> specific requirement.

I still think TDX is making this too hard, the S-EPT is controled by
the TSM right? Why doesn't it do the map/unmap of the MMIO as part of
the bind/unbind instead of this weird thing where the vPCI function
creation is split up between KVM and iommufd?

> Another more general requirement is, VFIO needs to trigger unbind when
> VFIO wants to actively invalidate MMIOs. e.g. before VFIO resets device.
> That is the dynamic unbind thing.

Alexey is right here, this is a userspace problem. VFIO should block
FLR on an bound device. Userspace has to unbind as part of its FLR
flow.

Jason