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

[<dan.j.williams@intel.com>]

Jonathan Cameron wrote:
> 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?

I think Yilun was staging some infrastructure early, will clean this and
other stuff up for the v1 posting.

> 
> 
> > +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.

Makes sense.