RE: [PATCH v8 10/15] PCI/TSM: Add vIOMMU-bound device contexts

[Tian, Kevin]

> From: Aneesh Kumar K.V (Arm) <aneesh.kumar@xxxxxxxxxx>
> Sent: Thursday, November 5, 2026 12:16 AM
> 
> An IOMMUFD vDEVICE represents a physical device within a virtual IOMMU
> (vIOMMU) for a guest. It must use the same TEE Security Manager as its
> vIOMMU. Pinning the vIOMMU backend keeps its tsm_dev registered, but
> does not preserve the connection between the physical function 0 (PF0)
> PCI device and that TSM.
> 
> Add a per-vDEVICE PCI TSM context. Verify that the PCI device and the
> vIOMMU use the same tsm_dev, and account active contexts on PF0. Reject
> disconnect with -EBUSY until all dependent vDEVICEs release their
> contexts.

We really don't need so many vIOMMU/vDEVICE notations here,
especially in following code/comments. It's just about a tsm context
which holds the pf0 from disconnected. Then let's describe/code it
from that angle.

> +struct pci_tsm_context *pci_tsm_context_get(struct pci_dev *pdev,
> +					    struct tsm_dev *viommu_tsm_dev)

could clarify that each get returns a new context even on a same device.

s/viommu_tsm_dev/tsm_dev/. It's just a parameter to be matched against.

>  {
> -	struct pci_tsm_pf0 *tsm_pf0;
> -	struct pci_tdi *tdi;
> -
> -	if (!kvm)
> -		return -EINVAL;
> +	struct pci_tsm_context *context;
> +	struct pci_tsm_pf0 *pf0;
> 
>  	guard(rwsem_read)(&pci_tsm_rwsem);
> +	if (!pdev->tsm || !is_link_tsm(pdev->tsm->tsm_dev))
> +		return ERR_PTR(-EOPNOTSUPP);
> +	/*
> +	 * The vdevice can use a different PCI function from VIOMMU_ALLOC.
> The
> +	 * module pin keeps the vIOMMU's TSM registered, but does not
> freeze this
> +	 * function's link. Match its current TSM before pinning the link below.
> +	 */

this is the example needing a rewrite...

> +	if (pdev->tsm->tsm_dev != viommu_tsm_dev)
> +		return ERR_PTR(-EXDEV);
> 
> -	if (!pdev->tsm)
> -		return -EINVAL;
> +	pf0 = to_pci_tsm_pf0(pdev->tsm);
> +	if (!pf0)
> +		return ERR_PTR(-ENXIO);

No need to check the return error as other places do?