Re: [PATCH v2 03/19] device core: Introduce confidential device acceptance

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Mar 26, 2026 at 11:31:16AM -0700, Dan Williams wrote:
> Jason Gunthorpe wrote:
> [..]
> > > I assume this would also expect that encrypted MMIO mappings are also
> > > not established while trust is less than "TCB"? That would require some
> > > additional enabling to catch attempts to establish an encrypted mapping
> > > that the hardware is prepared for, but dev->trust is not, all without
> > > needing to modify the driver to worry about this difference. Drivers
> > > would just see ioremap() failure in this case.
> > 
> > Hmm.. I don't know if this matters. Once we decide to use the device
> > the MMIO should be mapped in the correct way, whatever that is.
> > 
> > If we decide to eventually allow a lower trust while T=1 then that
> > should be taken to mean the user wants all the features protecting the
> > communication channel but also all the IOMMU features restricting what
> > memory the device can access.
> 
> The question is whether any part of the kernel would ever track that
> secrets in MMIO writes should not be written to TCB-external devices...
> but that is probably a "trust=0" situation. "trust=1" means "be careful
> what you send to this device whether the transport is protected or not".

Right, the kernel has no idea what is secret or not, it is up to
userspace not to give the device secrets if it doesn't fully trust it.

Jason