Re: [PATCH v4 1/5] acpi: Convert build_tpm2() to build_append* API

[Auger Eric <eric.auger@redhat.com>]

Hi Igor,

On 6/22/20 2:14 PM, Igor Mammedov wrote:
> On Mon, 22 Jun 2020 11:47:26 +0200
> Auger Eric <eric.auger@redhat.com> wrote:
> 
>> Hi Igor,
>>
>> On 6/22/20 11:39 AM, Igor Mammedov wrote:
>>> On Fri, 19 Jun 2020 07:19:51 -0400
>>> Stefan Berger <stefanb@linux.ibm.com> wrote:
>>>   
>>>> On 6/19/20 5:43 AM, Auger Eric wrote:  
>>>>> Hi Laszlo,
>>>>>
>>>>> On 6/19/20 11:38 AM, Laszlo Ersek wrote:    
>>>>>> On 06/18/20 09:50, Auger Eric wrote:    
>>>>>>> Hi Stefan, Igor,
>>>>>>>
>>>>>>> On 6/16/20 4:11 PM, Stefan Berger wrote:    
>>>>>>>> On 6/16/20 8:33 AM, Igor Mammedov wrote:    
>>>>>>>>> nevertheless looks like faithfull conversion,
>>>>>>>>> btw why you didn't drop Acpi20TPM2 structure definition?
>>>>>>>>>    
>>>>>>>> If we get rid of the table we should keep a reference to this document,
>>>>>>>> table 7: "TCG ACPI Specification; Family 1.2 and 2.0; Level 00 Revision
>>>>>>>> 00.37, December 19, 2014"
>>>>>>>>
>>>>>>>> https://trustedcomputinggroup.org/wp-content/uploads/TCG_ACPIGeneralSpecification_1-10_0-37-Published.pdf
>>>>>>>>
>>>>>>>>
>>>>>>>>    
>>>>>>> Further looking at this spec, the log_area_minimum_length and
>>>>>>> log_area_start_address only are described in
>>>>>>> - Table 2 (TCG Hardware InterfaceDescription Table Format for TPM 1.2
>>>>>>> Clients)
>>>>>>> - Table 4 (TCG Hardware Interface Description Table Format for TPM 1.2
>>>>>>> Servers)
>>>>>>> but not in Table 7, ie. not for TPM 2.0.
>>>>>>>
>>>>>>> Are they really needed for TPM2 or what do I miss?    
>>>>>> (side comment:
>>>>>>
>>>>>> LASA and LAML are optional with TPM-2.0. From the discussion at
>>>>>> <https://bugzilla.tianocore.org/show_bug.cgi?id=978>.    
>>>>
>>>>
>>>> They are needed for (x86) BIOS, such as SeaBIOS, not for UEFI, though. I 
>>>> do not know about ARM.
>>>>
>>>>  
>>>>> Thank you for the pointer and info. I failed to find this info in the
>>>>> spec. Given the risk of confusion, I would personally keep struct
>>>>> Acpi20TPM2 and maybe add a comment. Stefan?    
>>>>
>>>> Either way is fine with me for as long as we know where to find the 
>>>> layout of the structure.  
>>> I'd remove Acpi20TPM2 as it hardly documents anything, and add a comment
>>> pointing to the concrete spec that has these fields.
>>>
>>> TCGTCG ACPI SpecificationFamily “1.2” and “2.0”Version 1.2,Revision 8  
>>
>> [PATCH v6 0/3] vTPM/aarch64 ACPI support was posted.
>>
>> As documented in the cover letter (history log), the presence of the
>> LAML and LASA fields in the TPM2 table is not clearly documented in the
>> spec (at least I failed to find it). It is for TPM 1.2. On the other
>> hand, Stefan said it is mandated for some x86 BIOS to work. Given this
>> weirdness I think keeping the  Acpi20TPM2 struct is not too bad. See v6 ...
> 
> Laszlo pointed to spec version where LAML/LASA in TPM2 are documented,
> so I'd just use that as a spec this code is based on.

OK I missed that, indeed in the version the 2 fields are documented.
https://trustedcomputinggroup.org/wp-content/uploads/TCG_ACPIGeneralSpecification_v1.20_r8.pdf

in table 7:TCG Hardware Interface Description Table Format for TPM 2.0

I will use that ref and remove the Acpi20TPM2 struct then.

Thanks

Eric

> 
> PS:
> Acpi20TPM2 struct doesn't document anything, it's just another way to do
> the same thing as build_appen_* calls do. Having it just adds to confusion. 
> 
>>
>> Thanks
>>
>> Eric
>>>   
>>>>
>>>>    Stefan
>>>>  
>>>>>
>>>>> Thanks
>>>>>
>>>>> Eric    
>>>>>> )
>>>>>>
>>>>>> Thanks
>>>>>> Laszlo
>>>>>>    
>>>>  
>>>
>>>   
>