[PATCH v7 2/2] schemas: Add some common reserved-memory usages

[Chiu, Chasel]

Hi Ard,

Here is the POC PR for your reference: https://github.com/tianocore/edk2/pull/4969/files#diff-ccebabae5274b21634723a2111ee0de11bed6cfe8cb206ef9e263d9c5f926a9cR268
Please note that this PR is still in early phase and expected to have significant changes.

The idea is that payload entry will create gEfiMemoryTypeInformationGuid HOB with payload default memory types and allow FDT to override if correspond node present.
Please let me know if you have questions or suggestions.

Thanks,
Chasel


> -----Original Message-----
> From: Ard Biesheuvel <ardb at kernel.org>
> Sent: Tuesday, November 21, 2023 8:42 AM
> To: Simon Glass <sjg at chromium.org>
> Cc: Chiu, Chasel <chasel.chiu at intel.com>; devicetree at vger.kernel.org; Mark
> Rutland <mark.rutland at arm.com>; Rob Herring <robh at kernel.org>; Tan, Lean
> Sheng <sheng.tan at 9elements.com>; lkml <linux-kernel at vger.kernel.org>;
> Dhaval Sharma <dhaval at rivosinc.com>; Brune, Maximilian
> <maximilian.brune at 9elements.com>; Yunhui Cui <cuiyunhui at bytedance.com>;
> Dong, Guo <guo.dong at intel.com>; Tom Rini <trini at konsulko.com>; ron minnich
> <rminnich at gmail.com>; Guo, Gua <gua.guo at intel.com>; linux-
> acpi at vger.kernel.org; U-Boot Mailing List <u-boot at lists.denx.de>
> Subject: Re: [PATCH v7 2/2] schemas: Add some common reserved-memory
> usages
> 
> On Mon, 20 Nov 2023 at 21:12, Simon Glass <sjg at chromium.org> wrote:
> >
> > Hi,
> >
> > On Mon, 13 Nov 2023 at 11:09, Chiu, Chasel <chasel.chiu at intel.com> wrote:
> > >
> > >
> > > Hi Ard,
> > >
> > > Please see my reply below inline.
> > >
> > > Thanks,
> > > Chasel
> > >
> > >
> > > > -----Original Message-----
> > > > From: Ard Biesheuvel <ardb at kernel.org>
> > > > Sent: Saturday, November 11, 2023 3:04 AM
> > > > To: Chiu, Chasel <chasel.chiu at intel.com>
> > > > Cc: Simon Glass <sjg at chromium.org>; devicetree at vger.kernel.org;
> > > > Mark Rutland <mark.rutland at arm.com>; Rob Herring
> > > > <robh at kernel.org>; Tan, Lean Sheng <sheng.tan at 9elements.com>; lkml
> > > > <linux-kernel at vger.kernel.org>; Dhaval Sharma
> > > > <dhaval at rivosinc.com>; Brune, Maximilian
> > > > <maximilian.brune at 9elements.com>; Yunhui Cui
> > > > <cuiyunhui at bytedance.com>; Dong, Guo <guo.dong at intel.com>; Tom
> > > > Rini <trini at konsulko.com>; ron minnich <rminnich at gmail.com>; Guo,
> > > > Gua <gua.guo at intel.com>; linux- acpi at vger.kernel.org; U-Boot
> > > > Mailing List <u-boot at lists.denx.de>
> > > > Subject: Re: [PATCH v7 2/2] schemas: Add some common
> > > > reserved-memory usages
> > > >
> > > > On Sat, 11 Nov 2023 at 04:20, Chiu, Chasel <chasel.chiu at intel.com> wrote:
> > > > >
> > > > >
> > > > > Just sharing some usage examples from UEFI/EDK2 scenario.
> > > > > To support ACPI S4/Hibernation, memory map must be consistent
> > > > > before entering and after resuming from S4, in this case payload
> > > > > may need to know previous memory map from bootloader (currently
> > > > > generic payload cannot access platform/bootloader specific
> > > > > non-volatile data, thus could not save/restore memory map
> > > > > information)
> > > >
> > > > So how would EDK2 reconstruct the entire EFI memory map from just
> > > > these unannotated /reserved-memory nodes? The EFI memory map
> > > > contains much more information than that, and all of it has to
> > > > match the pre-hibernate situation, right? Can you given an example?
> > >
> > >
> > > Here we listed only typically memory types that may change cross different
> platforms.
> > > Reserved memory type already can be handled by reserved-memory node,
> and rest of the types usually no need to change cross platforms thus currently we
> could rely on default in generic payload.
> > > In the future if we see a need to add new memory types we will discuss and
> add it to FDT schema.
> > >
> > >
> > >
> > > >
> > > > > Another usage is to support binary model which generic payload
> > > > > is a prebuilt
> > > > binary compatible for all platforms/configurations, however the
> > > > payload default memory map might not always work for all the
> > > > configurations and we want to allow bootloader to override payload default
> memory map without recompiling.
> > > > >
> > > >
> > > > Agreed. But can you explain how a EDK2 payload might make
> > > > meaningful use of 'runtime-code' regions provided via DT  by the
> > > > non-EDK2 platform init? Can you give an example?
> > >
> > >
> > > Runtime-code/data is used by UEFI payload for booting UEFI OS which
> required UEFI runtime services.
> > > Platform Init will select some regions from the usable memory and assign it to
> runtime-code/data for UPL to consume. Or assign same runtime-code/data from
> previous boot.
> > > If UEFI OS is not supported, PlatformInit may not need to provide
> > > runtime-code/data regions to payload. (always providing
> > > runtime-code/data should be supported too)
> > >
> > >
> > > >
> > > > > Under below assumption:
> > > > >         FDT OS impact has been evaluated and taken care by
> > > > > relevant
> > > > experts/stakeholders.
> > > > > Reviewed-by: Chasel Chiu <chasel.chiu at intel.com>
> > > > >
> > > >
> > > > I am sorry but I don't know what 'FDT OS impact' means. We are
> > > > talking about a firmware-to-firmware abstraction that has the
> > > > potential to leak into the OS visible interface.
> > > >
> > > > I am a maintainer in the Tianocore project myself, so it would
> > > > help if you could explain who these relevant experts and
> > > > stakeholders are. Was this discussed on the edk2-devel mailing
> > > > list? If so, apologies for missing it but I may not have been cc'ed perhaps?
> > >
> > >
> > >
> > >
> > > I'm not familiar with FDT OS, also I do not know if who from edk2-devel were
> supporting FDT OS, I think Simon might be able to connect FDT OS
> experts/stakeholders.
> > > We are mostly focusing on payload firmware phase implementation in
> > > edk2 (and other payloads too), however, since we have aligned the
> > > payload FDT and OS FDT months ago, I'm assuming FDT OS impact must
> > > be there and we need (or already done?) FDT OS experts to support
> > > it. (again, maybe Simon could share more information about FDT OS)
> > >
> > > In edk2 such FDT schema is UefiPayloadPkg internal usage only and payload
> entry will convert FDT into HOB thus we expected the most of the edk2 generic
> code are no-touch/no impact, that's why we only had small group
> (UefiPayloadPkg) discussion.
> > > Ard, if you are aware of any edk2 code that's for supporting FDT OS, please let
> us know and we can discuss if those code were impacted or not.
> >
> > We discussed this and just to clarify, 'FDT OS' is not a special OS,
> > it is just Linux.
> >
> > So, with the above, are we all on the same page? Can the patch be
> > applied, perhaps? If not, what other discussion is needed?
> >
> 
> An example of how a platform-init/payload combination would make meaningful
> use of such runtime-code/data regions.