On Sep 18, 2014, at 10:38 PM, Narinder Dhillon <[email protected]> wrote:
> Hi All,
>
> In order to add ACPI tables to UEFI, iasl compiler has to be downloaded from
> acpica.org.
> UEFI build compiles the tables, which makes the configuration static.
> Is there any way to change this configuration from UEFI prompt or by calling
> UEFI functions ?
> For example, I have a 8 core ARMv8 ACPI table but I want to boot only 4
> cores. Is it possible to change this on the fly without editing and
> recompiling the ACPI tables ?
>
Some of the ACPI tables are just tables of data (*.aslc in edk2) and some are
the AML that requires iasl. The reason being early in the OS boot flow the ACPI
interpreter is not available. So info about the number of processors is in a
table not AML.
The only ACPI table code I see in the tree is in the OvmfPkg. You can see the
CPU tables (LocalApic) being constructed, after the code makes a call to the VM
to get the number of CPUs.
>git grep “APIC_STRUCTURE”
...
OvmfPkg/AcpiPlatformDxe/Qemu.c:75: EFI_ACPI_1_0_PROCESSOR_LOCAL_APIC_STRUCTURE
*LocalApic;
OvmfPkg/AcpiPlatformDxe/Qemu.c:76: EFI_ACPI_1_0_IO_APIC_STRUCTURE
*IoApic;
OvmfPkg/AcpiTables/Madt.aslc:51: EFI_ACPI_1_0_PROCESSOR_LOCAL_APIC_STRUCTURE
LocalApic[EFI_ACPI_PROCESSOR_LOCAL_APIC_COUNT];
OvmfPkg/AcpiTables/Madt.aslc:59: EFI_ACPI_1_0_IO_APIC_STRUCTURE
IoApic[EFI_ACPI_IO_APIC_COUNT];
OvmfPkg/AcpiTables/Madt.aslc:96: sizeof
(EFI_ACPI_1_0_PROCESSOR_LOCAL_APIC_STRUCTURE), // Length
OvmfPkg/AcpiTables/Madt.aslc:139: sizeof (EFI_ACPI_1_0_IO_APIC_STRUCTURE),
// Length
I’m not sure what ARM does, but for X86 the MADT is used and each table entry
has a flag field that can disable the processor.
Thanks,
Andrew Fish
> Thanx.
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