linux-kernel - Re: [PATCH v7 04/20] x86/virt/tdx: Add skeleton to initialize TDX on demand

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Message-ID: <e87b68ed-c51c-85aa-1cf9-7a67b8eebe00@intel.com>
Date:   Wed, 23 Nov 2022 08:58:56 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "Luck, Tony" <tony.luck@...el.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>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "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 v7 04/20] x86/virt/tdx: Add skeleton to initialize TDX on
 demand

On 11/23/22 02:18, Huang, Kai wrote:
>> Again, there are a lot of words in that comment, but I'm not sure why
>> it's here.  Despite all the whinging about ACPI, doesn't it boil down to:
>>
>>       The TDX module itself establishes its own concept of how many
>>       logical CPUs there are in the system when it is loaded.
>>
> This isn't accurate.  TDX MCHECK records the total number of logical CPUs when
> the BIOS enables TDX.  This happens before the TDX module is loaded.  In fact
> the TDX module only gets this information from a secret location.

Kai, this is the point where I lose patience with the conversation
around this series.  I'll you paste you the line of code where the TDX
module literally "establishes its own concept of how many logical CPUs
there are in the system":

>     //NUM_LPS
>     tdx_global_data_ptr->num_of_lps = sysinfo_table_ptr->mcheck_fields.tot_num_lps;

Yes, this is derived directly from MCHECK.  But, this concept is
separate from MCHECK.  We have seen zero actual facts from you or other
folks at Intel that this is anything other than an arbitrary choice made
for the convenience of the TDX module.  It _might_ not be this way.  I'm
open to hearing those facts and changing my position on this.

But, please bring facts, not random references to "secret locations"
that aren't that secret.