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

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Feb 01, 2017 at 12:37:39PM +0100, Igor Mammedov wrote:
> On Tue, 31 Jan 2017 20:17:02 +0200
> "Michael S. Tsirkin" <mst@redhat.com> 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.

Or just do what every hardware vendor does:
1. write according to spec
2. test a bunch of OSes, fix crashes


-- 
MST