Re: [Qemu-devel] [PATCH v2] i386/acpi: add _HID to processor objects

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 22 Oct 2015 22:03:24 +0200
Matthias Lange <matthias.lange@kernkonzept.com> wrote:

> This patch appends "ACPI0007" as the HID to each processor object.
> 
> Until commit 20843d processor objects used to have a _HID. According
> to the ACPI spec this is not required but removing it breaks systems
Pls answer Michael's question about motivation of this patch.
 i.e. what guests it exactly breaks?

> which relied on the HID. As it does no harm it is safe to add _HID
> to processor objects and restore the old behaviour.
> 
> Signed-off-by: Matthias Lange <matthias.lange@kernkonzept.com>
> ---
>  hw/i386/acpi-build.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 95e0c65..314cd0b 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -1153,6 +1153,9 @@ build_ssdt(GArray *table_data, GArray *linker,
>          for (i = 0; i < acpi_cpus; i++) {
>              dev = aml_processor(i, 0, 0, "CP%.02X", i);
>  
> +            /* for processor objects a _HID is not strictly required, however it
> +             * does no harm and preserves compatibility with other BIOSes */
> +            aml_append(dev, aml_name_decl("_HID", aml_string("ACPI0007")));
Spec doesn't tell anything about using ACPI0007 with Processor statement,
it's only mentioned in context of Device statement.

>              method = aml_method("_MAT", 0);
>              aml_append(method, aml_return(aml_call1("CPMA", aml_int(i))));
>              aml_append(dev, method);