linux-kernel - Re: [PATCH v11 20/20] Documentation/x86: Add documentation for TDX host support

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Date:   Mon, 12 Jun 2023 03:41:24 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Luck, Tony" <tony.luck@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v11 20/20] Documentation/x86: Add documentation for TDX
 host support

On Thu, 2023-06-08 at 16:56 -0700, Dave Hansen wrote:
> On 6/4/23 07:27, Kai Huang wrote:
> > +There is no CPUID or MSR to detect the TDX module.  The kernel detects it
> > +by initializing it.
> 
> Is this really what you want to say?
> 
> If the module is there, SEAMCALL works.  If not, it doesn't.  The module
> is assumed to be there when SEAMCALL works.  Right?
> 
> Yeah, that first SEAMCALL is probably an initialization call, but feel
> like that's beside the point.

Thanks for reviewing the documentation.

I guess I don't need to mention the "detection" part at all?


-TDX module detection and initialization
+TDX module initialization
 ---------------------------------------
 
-There is no CPUID or MSR to detect the TDX module.  The kernel detects it
-by initializing it.
-
 The kernel talks to the TDX module via the new SEAMCALL instruction.  The
 TDX module implements SEAMCALL leaf functions to allow the kernel to
 initialize it.
 
+If the TDX module isn't loaded, the SEAMCALL instruction fails with a
+special error.  In this case the kernel fails the module initialization
+and reports the module isn't loaded::
+
+  [..] tdx: Module isn't loaded.