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

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 09/02/2015 07:42 PM, Igor Mammedov wrote:
> 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.

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!