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Re: [Qemu-devel] [PATCH RFC] acpi: add reset register to fadt

From: Igor Mammedov
Subject: Re: [Qemu-devel] [PATCH RFC] acpi: add reset register to fadt
Date: Mon, 23 Jan 2017 12:12:04 +0100

On Thu, 19 Jan 2017 19:09:47 +0100
Phil Dennis-Jordan <address@hidden> wrote:

> On 18 January 2017 at 17:30, Michael S. Tsirkin <address@hidden> wrote:
> > I think what's important is the Fadt format revision. That one was 1 for 
> > 1.0b and 3 for 2.0.
> >
> > See page 112, Table 5-5 Fixed ACPI Description Table Format in acpi spec
> > 1.0b.
> >
> > Now look at page 110 in spec 2.0, this time
> > "Table 5-8 Fixed ACPI Description Table (FADT) Format".
> >
> > You will see that FADT revision is now 3, and there are a bunch of new
> > fields after the reset register. I think you have to fill them in,
> > you probably can get away with copying the non-extended values.  
> I've just spent a few hours fiddling around with this, and the results
> aren't good. WinXP and 7 seem absolutely fine with a rev3 (or rev5)
> FADT, presumably because they ignore it. macOS 10.12 hangs on boot
> with a fully filled out r3/5 FADT. If I skip filling out the
> Xdsdt/Xfacs addresses and just leave them at 0 it boots OK. Windows 10
> hangs or bluescreens ("ACPI BIOS ERROR") in either case. (I tested
> UEFI boot with OVMF, did not try legacy BIOS.)
> Just in case I'd messed up the code, I also tried this FADT patch
> https://lists.gnu.org/archive/html/qemu-devel/2016-08/msg02216.html
> from some months ago which evidently never got accepted. It yielded
> the same result as my independently developed implementation.
patch looks a bit wrong in filling x_fields, pls see spec first
before setting them.

> I don't really know enough about ACPI to have an intuition for what to
> try next. Unfortunately, macOS's ACPI table parser does not appear to
> be in any of the open source bits of the xnu kernel, otherwise I'd be
> looking there for hints.
> For reference, my approach to filling out the Xdsdt/Xfacs fields in
> build_fadt() is essentially the same as for the 32-bit variants from
> rev1:
> unsigned xfacs_offset = (char *)&fadt->Xfacs - table_data->data;
> bios_linker_loader_add_pointer(linker,
>         ACPI_BUILD_TABLE_FILE, xfacs_offset, sizeof(fadt->Xfacs),
>         ACPI_BUILD_TABLE_FILE, facs_tbl_offset);
> Suggestions welcome.
You are not supposed to fill in the same values in X_FOO as in FOO.
Spec says that only either one of above should be set.

X_FOO is typically is used for addresses above 4G and seabios
always allocates tables below 4G so you don't need to set
X_FOO variants unless you have to for some reason.

Read FADT fields description that you are modifying/adding
in respective ACPI spec http://www.uefi.org/acpi/specs

> Thanks,
> Phil

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