Re: [Qemu-devel] [PATCH] pc: acpi: keep pvpanic backward compatible

["Radim Krčmář" <rkrcmar@redhat.com>]

2015-05-29 10:51+0200, Igor Mammedov:
> On Wed, 27 May 2015 18:29:17 +0200
> Radim Krčmář <rkrcmar@redhat.com> wrote:
> > In the old times, we always had pvpanic in ACPI and a _STA function told
> > the guest not to use it.  Now, we only include pvpanic in ACPI if it is
> > enabled, so the _STA function is useless from qemu's point of view, but
> > guests still want to query availability.  Make them happy.
> maybe also fix guest's driver not to do since absence of _STA
> implies that device is present according to ACPI6.0 6.3.7 _STA

Will do.

> or only fix driver and drop this patch so that QEMU wouldn't carry
> useless junk.

I think we still want to run old guests on new versions of QEMU.
We could have kept the incremented _HID otherwise, it would be better.

> > (Why Linux does '& 0xb' on this result is completely beyond me.)
> check _STA related comment in SMC

(Time to actually open the spec ...)

> > +        method = aml_method("_STA", 0);
> > +        aml_append(method, aml_return(aml_int(0xf)));
> > +        aml_append(dev, method);
> doesn't have to be method,
> 
> make it like this:
>         /* device present, functioning, decoding, not shown in UI */
>         aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));

Nice, I didn't expect that much from the evaluator.

Thank you for all the information.
(v2 coming after I read few hundred pages.)