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

[Xiao Guangrong]

On 09/02/2015 06:06 PM, Igor Mammedov wrote:
> On Fri, 14 Aug 2015 22:51:55 +0800
> Xiao Guangrong <address@hidden> 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 <address@hidden>
> > ---
> >   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?