Re: [Qemu-devel] [PATCH] i386/acpi: add _HID to processor nodes

[Matthias Lange]

On 10/22/2015 01:48 PM, Michael S. Tsirkin wrote:
> On Thu, Oct 22, 2015 at 12:38:11PM +0200, Matthias Lange wrote:
>> Processor nodes created via the acpi/aml framework currently don't
>> feature a _HID string. This patch appends "ACPI0007" as the _HID
>> string to each processor node.
>>
>> Signed-off-by: Matthias Lange <address@hidden>
> 
> Indeed,  it does that.  But why?
> 
> ACPI0007 Processor Device. This device provides an alternative to
> declaring processors using the
> Processor ASL statement.
>  
> And “Declaring Processors” says
> 
> 
>       Each processor in the system must be declared in the ACPI namespace in
>       either the \_SB or \_PR
>       scope but not both. Declaration of processors in the \_PR scope is
>       required for platforms desiring
>       compatibility with ACPI 1.0-based OSPM implementations. Processors are
>       declared either via the
>       ASL Processor statement or the ASL Device statement. A Processor
>       definition declares a processor
>       object that provides processor configuration information and points to
>       the processor register block
>       (P_BLK). A Device definition for a processor is declared using the
>       ACPI0007 hardware identifier
>       (HID). In this case, processor configuration information is provided
>       exclusively by objects in the
>       processor device’s object list.

Thanks for pointing me to the right section.

> In other words, Processor directive does not need a HID.
> In fact, ACPI 1.0 didn't include the ACPI0007 HID at all.

Right. But, does Qemu strive for ACPI 1.0 compatibility? And e.g.
seabios also defines processors using the ALS processor statement
including the HID.

> Please include this info in both the commit log and a code comment.

Will do.

Matthias.

>> ---
>>  hw/i386/acpi-build.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>> index 95e0c65..95f7bf9 100644
>> --- a/hw/i386/acpi-build.c
>> +++ b/hw/i386/acpi-build.c
>> @@ -1153,6 +1153,7 @@ build_ssdt(GArray *table_data, GArray *linker,
>>          for (i = 0; i < acpi_cpus; i++) {
>>              dev = aml_processor(i, 0, 0, "CP%.02X", i);
>>  
>> +            aml_append(dev, aml_name_decl("_HID", aml_string("ACPI0007")));
>>              method = aml_method("_MAT", 0);
>>              aml_append(method, aml_return(aml_call1("CPMA", aml_int(i))));
>>              aml_append(dev, method);
>> -- 
>> 1.9.1


-- 
Matthias Lange, address@hidden, +49 - 351 - 41 88 86 14

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