On Wed, Mar 24, 2021 at 02:33 PM, Laszlo Ersek wrote:

> 
> 
>> 
>>> 
>>>> Hi all,
>>>> Would it be acceptable/feasible for AcpiTableDxe or AcpiPlatformDxe (in
>>>> MdeModulePkg) to use `EfiGetSystemConfigurationTable` to get the RSDP
>>>> and then install the tables? It's a solution that uses the regular
>>>> UefiLib, so it avoids platform-specific quirks (and as I see it, if RSDP
>>>> is in the configuration table, we probably always want those tables).
>>> 
>>> I'm sorry, I don't understand how this would help.
>> 
>> As I understand it, the issue is that this patchset changes MdeModulePkg
>> to do platform-specific parsing.
>> 
>> Perhaps it would be an acceptable solution for platforms to retrieve the
>> tables, then add
>> RSDP/them to the configuration table to be installed by
>> AcpiTableDxe/AcpiPlatformDxe.
>> This allows MdeModulePkg to abstract away the parsing, only installing
>> tables
>> available to it.
> 
> But this is already the best approach, and already what's happening --
> when you call EFI_ACPI_TABLE_PROTOCOL.InstallAcpiTable() from the
> platform's AcpiPlatformDxe, that's *how* you tell AcpiTableDxe in
> MdeModulePkg to pick up the table and hook it into the RSDT / XSDT /
> wherever, and also to manage RSD PTR as a UEFI configuration table.
> 
> Are you (more or less) proposing a new EFI_ACPI_TABLE_PROTOCOL member
> function for taking a forest of ACPI tables, passed in by RSD PTR?

Yes.
I thought the implementation of AcpiPlatformDxe in MdeModulePkg could take it, so it will install
ACPI tables from flash or from memory.

Regarding UefiPayloadPkg: gEfiAcpiTableGuid is not a HOB. It's an entry in
gUefiSystemTableInfoGuid (which is a HOB) that was installed in the config table. Therefore,
retrieving its GUID as a HOB in AcpiTableDxe fails.

To make this patchset work in UefiPayloadPkg (actually a fork), I have to add AcpiTableDxe to its
FDF, drop patch 2/2 and make `InstallAcpiTableFromHob` do
`Status = EfiGetSystemConfigurationTable (&gEfiAcpiTableGuid, (VOID **) &Rsdp);`.
Then, this patchset works: "acpiview" shell command shows tables from QEMU + coreboot, as well
as a BGRT.