Re: [RFC PATCH 03/27] coco/tdx-host: Support Link TSM for TDX host

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

On Fri, 19 Sep 2025 07:22:12 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> From: Xu Yilun <yilun.xu@linux.intel.com>
> 
> Register a Link TSM instance to support host side TSM operations for
> TDISP, when the TDX Connect support bit is set by TDX Module in
> tdx_feature0.
> 
> This is the main purpose of an independent tdx-host module out of TDX
> core. Recall that a TEE Security Manager (TSM) is a platform agent that
> speaks the TEE Device Interface Security Protocol (TDISP) to PCIe
> devices and manages private memory resources for the platform. An
> independent tdx-host module allows for device-security enumeration and
> initialization flows to be deferred from other TDX Module initialization
> requirements. Crucially, when / if TDX Module init moves earlier in x86
> initialization flow this driver is still guaranteed to run after IOMMU
> and PCI init (i.e. subsys_initcall() vs device_initcall()).
> 
> The ability to unload the module, or unbind the driver is also useful
> for debug and coarse grained transitioning between PCI TSM operation and
> PCI CMA operation (native kernel PCI device authentication).
> 
> For now this is the basic boilerplate with operation flows to be added
> later.
> 
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  arch/x86/include/asm/tdx.h            |   1 +
>  drivers/virt/coco/tdx-host/Kconfig    |   6 ++
>  drivers/virt/coco/tdx-host/tdx-host.c | 145 +++++++++++++++++++++++++-
>  3 files changed, 151 insertions(+), 1 deletion(-)
> 

> diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
> index 49c205913ef6..41813ba352d0 100644
> --- a/drivers/virt/coco/tdx-host/tdx-host.c
> +++ b/drivers/virt/coco/tdx-host/tdx-host.c

> +static struct pci_tsm_ops tdx_link_ops;
> +

Why is this needed?


> +static int tdx_connect_init(struct device *dev)
> +{
> +	struct tsm_dev *link;
> +
> +	if (!IS_ENABLED(CONFIG_TDX_CONNECT))
> +		return 0;
> +
> +	tdx_sysinfo = tdx_get_sysinfo();
> +	if (!tdx_sysinfo)
> +		return -ENXIO;
> +
> +	if (!(tdx_sysinfo->features.tdx_features0 & TDX_FEATURES0_TDXCONNECT))
> +		return 0;
> +
> +	link = tsm_register(dev, &tdx_link_ops);
> +	if (IS_ERR(link)) {
> +		dev_err(dev, "failed to register TSM: (%pe)\n", link);
> +		return PTR_ERR(link);

Might as well use
		return dev_err_probe(dev, PTR_ERR(link), "failed to register TSM\n");
as that will pretty print the error for you anyway and saves a few lines of code.

Thanks,

Jonathan