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

[Xiao Guangrong]

On 09/02/2015 07:42 PM, Igor Mammedov wrote:
> On Wed, 2 Sep 2015 18:43:41 +0800
> Xiao Guangrong <address@hidden> wrote:
>
> > 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?
> Probably it will, but why DSDT should be v2 for one of SSDT to be v2,
> they are separate tables.

When i made the first version of this patch, i only changed SSDT to v2 in 
build_ssdt()
but it failed, it worked only if both SSDT and DSDT were changed to v2. :(

I will confirm it again and figure it out.

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

That's great help to me, thanks for your sharing, Igor!