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

[Igor Mammedov]

On Tue, 31 Jan 2017 20:17:02 +0200
"Michael S. Tsirkin" <address@hidden> wrote:

> On Tue, Jan 31, 2017 at 05:28:57PM +0100, Laszlo Ersek wrote:
> > The ACPI 6.1 spec says,
> > 
> > - DSDT: [...] If the X_DSDT field contains a non-zero value then this
> >   field must be zero.
> > - X_DSDT: [...] If the DSDT field contains a non-zero value then this
> >   field must be zero.  
> 
> But that's only 6.1. 6.0 and earlier did not say this.
> The errata they wanted to address was:
> 1393 In FADT: if X_DSDT field is non-zero, DSDT
> field should be ignored or deprecated
> 
> I would class this as a spec bug.
> 

The same applies to X_PM1a_EVT_BLK and co,
for example 5.1 spec "This is a required
field."

And looks like Windows implemented it as mandatory
to boot perhaps to be compatible with 5.1 and earlier
specs.

It appears fw would be forced to fill fields depending
on table revision.