Re: [PATCH 4/6] PCI/TSM: Add pci_tsm_bind() helper for instantiating TDIs

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

On Tue,  4 Nov 2025 20:00:53 -0800
Dan Williams <dan.j.williams@intel.com> wrote:

> After a PCIe device has established a secure link and session between a TEE
> Security Manager (TSM) and its local Device Security Manager (DSM), the
> device or its subfunctions are candidates to be bound to a private memory
> context, a TVM. A PCIe device function interface assigned to a TVM is a TEE
> Device Interface (TDI).
> 
> The pci_tsm_bind() requests the low-level TSM driver to associate the
> device with private MMIO and private IOMMU context resources of a given TVM
> represented by a @kvm argument. A device in the bound state corresponds to
> the TDISP protocol LOCKED state and awaits validation by the TVM. It is a
> 'struct pci_tsm_link_ops' operation because, similar to IDE establishment,
> it involves host side resource establishment and context setup on behalf of
> the guest. It is also expected to be performed lazily to allow for
> operation of the device in non-confidential "shared" context for pre-lock
> configuration.
> 
> 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>
Trivial comments only from me.

> diff --git a/drivers/pci/tsm.c b/drivers/pci/tsm.c
> index 6a2849f77adc..f0e38d7fee38 100644
> --- a/drivers/pci/tsm.c
> +++ b/drivers/pci/tsm.c


> +/**
> + * pci_tsm_bind() - Bind @pdev as a TDI for @kvm
> + * @pdev: PCI device function to bind
> + * @kvm: Private memory attach context
> + * @tdi_id: Identifier (virtual BDF) for the TDI as referenced by the TSM and DSM
> + *
> + * Returns 0 on success, or a negative error code on failure.
> + *
> + * Context: Caller is responsible for constraining the bind lifetime to the
> + * registered state of the device. For example, pci_tsm_bind() /
> + * pci_tsm_unbind() limited to the VFIO driver bound state of the device.
> + */
> +int pci_tsm_bind(struct pci_dev *pdev, struct kvm *kvm, u32 tdi_id)
> +{
> +	struct pci_tsm_pf0 *tsm_pf0;
> +	struct pci_tdi *tdi;
> +
> +	if (!kvm)
> +		return -EINVAL;
> +
> +	guard(rwsem_read)(&pci_tsm_rwsem);
> +
> +	if (!pdev->tsm)
> +		return -EINVAL;
> +
> +	if (!is_link_tsm(pdev->tsm->tsm_dev))
> +		return -ENXIO;
> +
> +	tsm_pf0 = to_pci_tsm_pf0(pdev->tsm);
> +	guard(mutex)(&tsm_pf0->lock);
> +
> +	/* Resolve races to bind a TDI */
> +	if (pdev->tsm->tdi) {
> +		if (pdev->tsm->tdi->kvm == kvm)
> +			return 0;
I'd flip so the error case is out of line. Then drop the else.


		if (pdev->tsm->tdi->kvm != kvm)
			return -EBUSY;

		return 0;

> +		else
> +			return -EBUSY;
> +	}
> +
> +	tdi = to_pci_tsm_ops(pdev->tsm)->bind(pdev, kvm, tdi_id);
> +	if (IS_ERR(tdi))
> +		return PTR_ERR(tdi);
> +
> +	pdev->tsm->tdi = tdi;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_tsm_bind);