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

[Moore, Robert]

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
> ==========================================================================
> ===