linux-kernel - Re: [RFC PATCH 07/20] x86/virt/tdx: Expose SEAMLDR information via sysfs

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Message-ID: <aIwhUb3z9/cgsMwb@yilunxu-OptiPlex-7050>
Date: Fri, 1 Aug 2025 10:07:13 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: dan.j.williams@...el.com
Cc: Chao Gao <chao.gao@...el.com>, linux-coco@...ts.linux.dev,
	x86@...nel.org, kvm@...r.kernel.org, seanjc@...gle.com,
	pbonzini@...hat.com, eddie.dong@...el.com,
	kirill.shutemov@...el.com, dave.hansen@...el.com,
	kai.huang@...el.com, isaku.yamahata@...el.com,
	elena.reshetova@...el.com, rick.p.edgecombe@...el.com,
	Farrah Chen <farrah.chen@...el.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 07/20] x86/virt/tdx: Expose SEAMLDR information via
 sysfs

On Thu, Jul 31, 2025 at 02:01:21PM -0700, dan.j.williams@...el.com wrote:
> Xu Yilun wrote:
> > > +static const struct attribute_group *tdx_subsys_groups[] = {
> > > +	SEAMLDR_GROUP,
> > > +	NULL,
> > > +};
> > > +
> > >  static void tdx_subsys_init(void)
> > >  {
> > >  	struct tdx_tsm *tdx_tsm;
> > >  	int err;
> > >  
> > > +	err = get_seamldr_info();
> > > +	if (err) {
> > > +		pr_err("failed to get seamldr info %d\n", err);
> > > +		return;
> > > +	}
> > > +
> > >  	/* Establish subsystem for global TDX module attributes */
> > > -	err = subsys_virtual_register(&tdx_subsys, NULL);
> > > +	err = subsys_virtual_register(&tdx_subsys, tdx_subsys_groups);
> > >  	if (err) {
> > >  		pr_err("failed to register tdx_subsys %d\n", err);
> > >  		return;
> > 
> > As mentioned, TDX Connect also uses this virtual TSM device. And I tend
> > to extend it to TDX guest, also make the guest TSM management run on
> > the virtual device which represents the TDG calls and TDG_VP_VM calls.
> > 
> > So I'm considering extract the common part of tdx_subsys_init() out of
> > TDX host and into a separate file, e.g.
> > 
> > ---
> > 
> > +source "drivers/virt/coco/tdx-tsm/Kconfig"
> > +
> >  config TSM
> >         bool
> > diff --git a/drivers/virt/coco/Makefile b/drivers/virt/coco/Makefile
> > index c0c3733be165..a54d3cb5b4e9 100644
> > --- a/drivers/virt/coco/Makefile
> > +++ b/drivers/virt/coco/Makefile
> > @@ -10,3 +10,4 @@ obj-$(CONFIG_INTEL_TDX_GUEST) += tdx-guest/
> >  obj-$(CONFIG_ARM_CCA_GUEST)    += arm-cca-guest/
> >  obj-$(CONFIG_TSM)              += tsm-core.o
> >  obj-$(CONFIG_TSM_GUEST)                += guest/
> > +obj-y                          += tdx-tsm/
> > diff --git a/drivers/virt/coco/tdx-tsm/Kconfig b/drivers/virt/coco/tdx-tsm/Kconfig
> > new file mode 100644
> > index 000000000000..768175f8bb2c
> > --- /dev/null
> > +++ b/drivers/virt/coco/tdx-tsm/Kconfig
> > @@ -0,0 +1,2 @@
> > +config TDX_TSM_BUS
> > +       bool
> > diff --git a/drivers/virt/coco/tdx-tsm/Makefile b/drivers/virt/coco/tdx-tsm/Makefile
> > new file mode 100644
> > index 000000000000..09f0ac08988a
> > --- /dev/null
> > +++ b/drivers/virt/coco/tdx-tsm/Makefile
> > @@ -0,0 +1 @@
> > +obj-$(CONFIG_TDX_TSM_BUS) += tdx-tsm-bus.o
> 
> Just name it bus.c.

I'm about to make the change but I see there is already tdx-guest misc
virtual device in Guest OS:

  What:		/sys/devices/virtual/misc/tdx_guest/xxxx

And if we add another tdx_subsys, we have:

  What:		/sys/devices/virtual/tdx/xxxx

Do we really want 2 virtual devices? What's their relationship? I can't
figure out.

So I'm considering reuse the misc/tdx_guest device as a tdx root device
in guest. And that removes the need to have a common tdx tsm bus.

What do you think?

> 
> > ---
> > 
> > And put the tdx_subsys_init() in tdx-tsm-bus.c. We need to move host
> > specific initializations out of tdx_subsys_init(), e.g. seamldr_group &
> > seamldr fw upload.
> 
> Just to be clear on the plan here as I think this TD Preserving set
> should land before we start upstreamming any TDX Connect bits.
> 
> - Create drivers/virt/coco/tdx-tsm/bus.c for registering the tdx_subsys.
>   The tdx_subsys has sysfs attributes like "version" (host and guest
>   need this, but have different calls to get at the information) and
>   "firmware" (only host needs that). So the common code will take sysfs
>   groups passed as a parameter.
> 
> - The "tdx_tsm" device which is unused in this patch set can be

It is used in this patch, Chao creates tdx module 'version' attr on this
device. But I assume you have different opinion: tdx_subsys represents
the whole tdx_module and should have the 'version', and tdx_tsm is a
sub device dedicate for TDX Connect, is it?

Thanks,
Yilun

>   registered on the "tdx" bus to move feature support like TDX Connect
>   into a typical driver model.
> 
> So the change for this set is create a bus.c that is host/guest
> agnostic, drop the tdx_tsm device and leave that to the TDX Connect
> patches to add back. 
> 
> The TDX Connect pathes will register the tdx_tsm device near where the
> bus is registered for the host and guest cases.
> 
> Concerns?
> 
> In the meantime, until this set lands in tip we can work out the
> organization in tsm.git#staging.