Re: [PATCH 5/6] PCI/TSM: Add pci_tsm_guest_req() for managing TDIs

Jonathan Cameron
2025-11-05T15:38:06Z

On Tue, 4 Nov 2025 20:00:54 -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>
More triviality inline.

> diff --git a/drivers/pci/tsm.c b/drivers/pci/tsm.c
> index f0e38d7fee38..4dd518b45eea 100644
> --- a/drivers/pci/tsm.c
> +++ b/drivers/pci/tsm.c
> @@ -354,6 +354,69 @@ int pci_tsm_bind(struct pci_dev *pdev, struct kvm *kvm, u32 tdi_id)
> }
> EXPORT_SYMBOL_GPL(pci_tsm_bind);

> +ssize_t pci_tsm_guest_req(struct pci_dev *pdev, enum pci_tsm_req_scope scope,
> + sockptr_t req_in, size_t in_len, sockptr_t req_out,
> + size_t out_len, u64 *tsm_code)
> +{
> + struct pci_tsm_pf0 *tsm_pf0;
> + struct pci_tdi *tdi;
> + int rc;
> +
> + /*
> + * Forbid requests that are not directly related to TDISP
> + * operations
> + */

/* Forbid requests that are not directly related to TDISP operations */
Is just under 80 chars.

> + */