linux-kernel - Re: [RFC PATCH v1 09/38] iommufd/vdevice: Add TSM Guest request uAPI

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Message-ID: <20250804220352.GA3644611@bhelgaas>
Date: Mon, 4 Aug 2025 17:03:52 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
Cc: linux-coco@...ts.linux.dev, kvmarm@...ts.linux.dev,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	aik@....com, lukas@...ner.de, Samuel Ortiz <sameo@...osinc.com>,
	Xu Yilun <yilun.xu@...ux.intel.com>, Jason Gunthorpe <jgg@...pe.ca>,
	Suzuki K Poulose <Suzuki.Poulose@....com>,
	Steven Price <steven.price@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>
Subject: Re: [RFC PATCH v1 09/38] iommufd/vdevice: Add TSM Guest request uAPI

On Mon, Jul 28, 2025 at 07:21:46PM +0530, Aneesh Kumar K.V (Arm) wrote:
> Add TSM Guest request uAPI against iommufd_vdevice to forward various
> TSM attestation & acceptance requests from guest to TSM driver/secure
> firmware. This uAPI takes function only after TSM Bind.
> 
> After a vPCI device is locked down by TSM Bind, CoCo VM should attest
> and accept the device in its TEE. These operations needs interaction
> with secure firmware and the device, but doesn't impact the device
> management from host's POV. It doesn't change the fact that host should
> not touch some part of the device (see TDISP spec) to keep the trusted
> assignment, and host could exit trusted assignment and roll back
> everything by TSM Unbind.
> 
> So the TSM Guest request becomes a passthrough channel for CoCo VM to
> exchange request/response blobs with TSM driver/secure firmware. The
> definition of this IOCTL illustates this idea.

s/illustates/illustrates/

> +++ b/drivers/pci/tsm.c
> @@ -861,7 +861,7 @@ int pci_tsm_unbind(struct pci_dev *pdev)
>  EXPORT_SYMBOL_GPL(pci_tsm_unbind);
>  
>  /**
> - * pci_tsm_guest_req - VFIO/IOMMUFD helper to handle guest requests
> + * pci_tsm_guest_req - IOMMUFD helper to handle guest requests
>   * @pdev: @pdev representing a bound tdi

I dunno where this got added (not this patch), but "TDI" might be an
initialism that should be capitalized?

>   * @info: envelope for the request
>   *
> @@ -871,11 +871,12 @@ EXPORT_SYMBOL_GPL(pci_tsm_unbind);
>   * posts to userspace (e.g. QEMU) that holds the host-to-guest RID
>   * mapping.
>   */
> -int pci_tsm_guest_req(struct pci_dev *pdev, struct pci_tsm_guest_req_info *info)
> +static int __pci_tsm_guest_req(struct pci_dev *pdev, struct tsm_guest_req_info *info)
>  {
>  	struct pci_tdi *tdi;
>  	int rc;
>  
> +

Spurious diff.

>  	lockdep_assert_held_read(&pci_tsm_rwsem);
>  
>  	if (!pdev->tsm)