Re: [edk2-devel] [Patch V2 0/2] Let AcpiTableDxe driver install Acpi table from Hob

["Guo Dong" <guo.dong@intel.com>]

Add my comments on the ideas behind.
UefiPayloadPkg is not a platform specific package, it tries to provide a generic payload using platform independent Modules. This allows to reuse the payload for different boot firmware solutions (Slim Bootloader, Coreboot, EDK2 bootloader) on different platforms.

Just like other DXE modules (e.g. variable DXE driver,  firmware performance DXE driver), standardizing and modularizing platform independent modules through a HOB as the AcpiTableDxe patch did to support potential data from PEI/bootloader is a nature way for EDKII modules reuse. Understood the concerns to keep AcpiTableDxe as simple as possible. I think it deserve for code reuse by adding PEI/bootloader HOB support.

Thanks,
Guo

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Laszlo
> Ersek
> Sent: Tuesday, March 23, 2021 5:40 AM
> To: Liu, Zhiguang <zhiguang.liu@intel.com>; Ni, Ray <ray.ni@intel.com>; Dong,
> Guo <guo.dong@intel.com>
> Cc: devel@edk2.groups.io; Wang, Jian J <jian.j.wang@intel.com>; Wu, Hao A
> <hao.a.wu@intel.com>; Bi, Dandan <dandan.bi@intel.com>; Liming Gao
> <gaoliming@byosoft.com.cn>
> Subject: Re: [edk2-devel] [Patch V2 0/2] Let AcpiTableDxe driver install Acpi
> table from Hob
> 
> On 03/23/21 04:24, Zhiguang Liu wrote:
> > If HOB contains APCI table information, entry point of AcpiTableDxe.inf
> > should parse the APCI table from HOB, and install these tables.
> > We assume the whole ACPI table (starting with
> EFI_ACPI_2_0_ROOT_SYSTEM_DESCRIPTION_POINTER)
> > is contained by a single gEfiAcpiTableGuid HOB.
> > This way, for UefiPayloadPkg, there is no need to specially hanle acpi table.
> >
> > Zhiguang Liu (2):
> >   MdeModulePkg/ACPI: Install ACPI table from HOB.
> >   UefiPayloadPkg: Remove code that installs APCI
> >
> >  MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableDxe.inf    |   3 ++-
> >  MdeModulePkg/Universal/Acpi/AcpiTableDxe/AcpiTableProtocol.c | 134
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
> ----
> >  UefiPayloadPkg/BlSupportDxe/BlSupportDxe.c                   |  13 ++-----------
> >  UefiPayloadPkg/BlSupportDxe/BlSupportDxe.h                   |   5 +----
> >  UefiPayloadPkg/BlSupportDxe/BlSupportDxe.inf                 |   5 ++---
> >  5 files changed, 133 insertions(+), 27 deletions(-)
> >
> 
> Where does this idea come from?
> 
> (1) There is no bugzilla for this, apparently (not linked in the commit
> messages anyway).
> 
> (2) Also, I'm not sure if reusing an existing (and standardized) GUID
> for this purpose is a good idea. I think an edk2-only
> (MdeModulePkg-defined), brand new GUID, for the HOB, would be better.
> 
> (3) I'm also not convinced at all that this *whole approach* is sound.
> 
> The fact that UefiPayloadPkg has the ACPI content available to it in a
> particular data representation (as a HOB, for example) is just a
> platform trait. Why should that platform trait leak into the central
> implementation of the ACPI table protocol?
> 
> UefiPayloadPkg can call the ACPI table protocol interfaces to install
> its tables. OVMF does the same -- OVMF also does not construct its own
> ACPI tables, but downloads them in a quirky representation from QEMU. We
> didn't hack the central AcpiTableDxe driver for that use case; instead,
> we dissected the blob (in OvmfPkg) into individual tables, and called
> the proper ACPI table protocol method (InstallAcpiTable()) with the
> individual tables.
> 
> I disagree with the code complexity / platform quirk in AcpiTableDxe. At
> the bare minimum, this feature should be possible to compile out
> altogether. I don't necessarily mean a FeaturePCD; there could be a new
> INF file too, that shares most of the functionality with the current
> core driver, but also includes (from a different source file) the new logic.
> 
> But I'd really like if this mess were kept out of MdeModulePkg
> altogether. It's the job of the platform ACPI driver to use the ACPI
> table protocol.
> 
> Of course if you can show that this HOB usage is standard / publicly
> specified, that's different.
> 
> Please do not merge this series.
> 
> Laszlo
> 
> 
> 
> 
>