Re: [PATCH v2 7/8] PCI/TSM: Add pci_tsm_guest_req() for managing TDIs

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Wed, 12 Nov 2025 18:14:45 -0800
Dan Williams <dan.j.williams@intel.com> wrote:

> A PCIe device function interface assigned to a TVM is a TEE Device
> Interface (TDI). A TDI instantiated by pci_tsm_bind() needs additional
> steps taken by the TVM to be accepted into the TVM's Trusted Compute
> Boundary (TCB) and transitioned to the RUN state.
> 
> pci_tsm_guest_req() is a channel for the guest to request TDISP collateral,
> like Device Interface Reports, and effect TDISP state changes, like
> LOCKED->RUN transititions. Similar to IDE establishment and pci_tsm_bind(),
> these are long running operations involving SPDM message passing via the
> DOE mailbox.
> 
> The path for a TVM to invoke pci_tsm_guest_req() is:
> * TSM triggers exit via guest-to-host-interface ABI (implementation specific)
> * VMM invokes handler (KVM handle_exit() -> userspace io)
> * handler issues request (userspace io handler -> ioctl() ->
>   pci_tsm_guest_req())
> * handler supplies response
> * VMM posts response, notifies/re-enters TVM
> 
> This path is purely a transport for messages from TVM to platform TSM. By
> design the host kernel does not and must not care about the content of
> these messages. I.e. the host kernel is not in the TCB of the TVM.
> 
> As this is an opaque passthrough interface, similar to fwctl, the kernel
> requires that implementations stay within the bounds defined by 'enum
> pci_tsm_req_scope'. Violation of those expectations likely has market and
> regulatory consequences. Out of scope requests are blocked by default.
> 
> Co-developed-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>