Re: [Qemu-devel] [PATCH v2 02/18] i386/acpi-build: allow SSDT to operate on 64 bit

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 2 Sep 2015 18:43:41 +0800
Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:

> 
> 
> On 09/02/2015 06:06 PM, Igor Mammedov wrote:
> > On Fri, 14 Aug 2015 22:51:55 +0800
> > Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:
> >
> >> Only 512M is left for MMIO below 4G and that are used by PCI, BIOS etc.
> >> Other components also reserve regions from their internal usage, e.g,
> >> [0xFED00000, 0xFED00000 + 0x400) is reserved for HPET
> >>
> >> Switch SSDT to 64 bit to use the huge free room above 4G. In the later
> >> patches, we will dynamical allocate free space within this region which
> >> is used by NVDIMM _DSM method
> >>
> >> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> >> ---
> >>   hw/i386/acpi-build.c  | 4 ++--
> >>   hw/i386/acpi-dsdt.dsl | 2 +-
> >>   2 files changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> >> index 46eddb8..8ead1c1 100644
> >> --- a/hw/i386/acpi-build.c
> >> +++ b/hw/i386/acpi-build.c
> >> @@ -1348,7 +1348,7 @@ build_ssdt(GArray *table_data, GArray *linker,
> >>       g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
> >>       build_header(linker, table_data,
> >>           (void *)(table_data->data + table_data->len - ssdt->buf->len),
> >> -        "SSDT", ssdt->buf->len, 1);
> >> +        "SSDT", ssdt->buf->len, 2);
> > That might break Windows XP, since it supports only 1.0b ACPI with some
> > 2.0 extensions.
> > there is 2 way to work around it:
> >   - add an additional Rev2 ssdt table if NVDIMMs are present
> >     and describe them there
> 
> I like this way, it's more straightforward to me.
> 
> BTW, IIUC the DSDT still need to be changed to Rev2 to recognise SSDT with Rev2,
> does it hurt Windows XP?
Probably it will, but why DSDT should be v2 for one of SSDT to be v2,
they are separate tables.

Also you might find following interesting wrt Windows compatibility
http://www.acpi.info/presentations/S01USMOBS169_OS%20new.ppt