Re: [Qemu-devel] [edk2] Windows does not support DataTableRegion at all [was: docs: describe QEMU's VMGenID design]

[Laszlo Ersek]

On 09/14/15 19:23, Walz, Michael C wrote:
> Who are the Microsoft representatives in the ASWG? Shouldn't this 
> conversation be happening with them?

I asked my colleague Al Stone @RH for help; he said he'd bring this up
at the next ASWG meeting. Thank you Al, and thank you Michael for the
suggestion.

Thanks!
Laszlo

> 
> -----Original Message-----
> From: Moore, Robert 
> Sent: September 14, 2015 10:14
> To: Bill Paul; address@hidden
> Cc: Laszlo Ersek; Igor Mammedov; Michael S. Tsirkin; Josh Triplett; Gal 
> Hammer; edk2-devel-01; address@hidden; Paolo Bonzini; Gough, Robert; Walz, 
> Michael C
> Subject: RE: [edk2] [Qemu-devel] Windows does not support DataTableRegion at 
> all [was: docs: describe QEMU's VMGenID design]
> 
> The Windows ACPI implementation doesn't even fully support ACPI 2.0 AFAIK, 
> let alone other new things.
> 
> Rob Gough or Michael may know better than I do.
> 
> 
>> -----Original Message-----
>> From: Bill Paul [mailto:address@hidden
>> Sent: Monday, September 14, 2015 9:53 AM
>> To: address@hidden
>> Cc: Laszlo Ersek; Igor Mammedov; Michael S. Tsirkin; Josh Triplett; 
>> Gal Hammer; edk2-devel-01; Moore, Robert; address@hidden; Paolo 
>> Bonzini
>> Subject: Re: [edk2] [Qemu-devel] Windows does not support 
>> DataTableRegion at all [was: docs: describe QEMU's VMGenID design]
>>
>> Of all the gin joints in all the towns in all the world, Laszlo Ersek 
>> had to walk into mine at 03:24:42 on Monday 14 September 2015 and say:
>>
>>> On 09/14/15 10:24, Igor Mammedov wrote:
>>>> On Sun, 13 Sep 2015 15:34:51 +0300
>>>>
>>>> "Michael S. Tsirkin" <address@hidden> wrote:
>>>>> On Sun, Sep 13, 2015 at 01:56:44PM +0200, Laszlo Ersek wrote:
>>>>>> As the subject suggests, I have terrible news.
>>>>>>
>>>>>> I'll preserve the full context here, so that it's easy to scroll 
>>>>>> back to the ASL for reference.
>>>>>>
>>>>>> I'm also CC'ing edk2-devel, because a number of BIOS developers 
>>>>>> should be congregating there.
>>>>>
>>>>> Wow, bravo! It does look like we need to go back to the drawing 
>>>>> board.
>>
>> I read your original post on this with great interest, and I applaud 
>> your determination in tracking this down. Nice job. Sadly, it seems 
>> you too have fallen victim to the "If It Works With Windows, It Must Be Ok"
>> syndrome.
>>
>> Now, I realize that as far as this particular situation is concerned, 
>> even if Microsoft decided to add support for DataTableRegion() 
>> tomorrow, it wouldn't really help because there are too many different 
>> versions of Windows in the field and there's no way to retroactively patch 
>> them all.
>> (Gee, that sounds
>> familiar...)
>>
>> Nevertheless, am I correct in saying that this is in fact a bug in 
>> Microsoft's ACPI implementation (both in their ASL compiler and in the 
>> AML parser)? Unless
>> DataTableRegion() is specified to be optional in some way (I don't 
>> know if it is or not, but I doubt it), this sounds like an clear cut 
>> case of non- compliance with the ACPI spec. And if that's true, isn't 
>> there any way to get Microsoft to fix it?
>>
>> -Bill
>>
>>>> I suggest we go back to the last Gal's series which is though not 
>>>> universal but a simple and straightforward solution.
>>>> That series with comments addressed probably is what we need in 
>>>> the end.
>>>
>>> I agree (I commented the same on the RHBZ too). The only one 
>>> requirement we might not satisfy with that is that the page 
>>> containing the generation ID must always be mapped as cacheable. In 
>>> practice it doesn't seem to cause issues.
>>>
>>> We tried to play nice, but given that (a) the vmgenid doc doesn't 
>>> mention a real requirement about the _CRS -- ie. no IO descriptors 
>>> are allowed to be in it --, (b) Windows doesn't support 
>>> DataTableRegion(), I doubt we could cover our bases 100% anyway. 
>>> There can be any number of further hidden requirements, and hidden 
>>> gaps in ACPI support too, so it's just business as usual with 
>>> Windows: whatever works, works, don't ask why.
>>>
>>> Just my opinion of course.
>>>
>>> Laszlo
>>>
>>>>> The only crazy thing you didn't try is to use an XSDT instead of 
>>>>> the DSDT.
>>>>> I find it unlikely that this will help ...
>>>
>>> _______________________________________________
>>> edk2-devel mailing list
>>> address@hidden
>>> https://lists.01.org/mailman/listinfo/edk2-devel
>>
>> --
>> ======================================================================
>> ====
>> ===
>> -Bill Paul            (510) 749-2329 | Senior Member of Technical Staff,
>>                  address@hidden | Master of Unix-Fu - Wind River 
>> Systems 
>> ======================================================================
>> ====
>> ===
>>    "I put a dollar in a change machine. Nothing changed." - George 
>> Carlin 
>> ======================================================================
>> ====
>> ===