Re: [PATCH v8 12/15] iommufd/viommu: Allow PCI TSM backends to provide vIOMMU operations

[Jason Gunthorpe]

On Wed, Nov 04, 2026 at 03:23:51PM -0800, Jacob Pan wrote:

> I am thinking MSHV/pKVM can register an assignment-only tsm_dev to
> leverage this? Could PCI/TSM support this role without device-security?

It is certainly not what TSM was originally imagined for, but with our
new arrangement, yah maybe so?

TSM basically just becomes this weird overlay driver on the PCI device
that does stuff. Some of the stuff it might do:
 - Register an attestation subsystem device to do SPDM
 - Register to allow iommufd to create a viommu
 - Some status sysfs ?
 - ??

It all seems separable and composable to me, so if you don't want to
launch an attestation subsystem device because there is no SPDM then I
think that might be OK?

Another option would be to somehow obtain the viommu from the kvm file
descriptor and rely on the fd to handle the module pinning/etc. I
don't know how to do that nicely with the way the modules work
though..

Jason