Re: 回复: 回复: [edk2-devel] [PATCH 1/3] MdeModulePkg/AcpiTableDxe: use pool allocations when possible

[Laszlo Ersek]

On 10/26/20 08:42, Ard Biesheuvel wrote:
> On 10/26/20 7:25 AM, Laszlo Ersek wrote:
>> On 10/26/20 02:35, gaoliming wrote:
>>> Ard:
>>>    I verify this patch on OvmfX64 and collect the memmap info. I
>>> don't see the difference in memmap.
>>>    So, this enhancement is for AARCH64 only. Is it right?
>>
>> That's my understanding, yes. OVMF enables ACPI 1.0b support in the
>> bitmask PCD, and so the compat code for 32-bit allocations (= page
>> allocations for expressing the 4GB limit) remains active.
>>
> 
> Indeed. Any platform that removes BIT1 from
> 
> gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiExposedTableVersions
> 
> will switch over to pool allocations, but OVMF retains support for ACPI
> 1.0b for some reason.
> 

I believe OVMF has always had that bit set, and clearing it would risk
regressions.

The ACPI (AML) generator in QEMU tends restricts itself to ACPI 1.0
constructs (opcodes) because at least the Windows 7 guest OS family
cannot deal with ACPI 2.0, as far as I remember.

Thanks,
Laszlo



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