On Tue, 28 Nov 2023 at 21:31, Chiu, Chasel <chasel.chiu@xxxxxxxxx> wrote: > > > > > > -----Original Message----- > > From: Ard Biesheuvel <ardb@xxxxxxxxxx> > > Sent: Tuesday, November 28, 2023 10:08 AM > > To: Chiu, Chasel <chasel.chiu@xxxxxxxxx> > > Cc: Simon Glass <sjg@xxxxxxxxxxxx>; devicetree@xxxxxxxxxxxxxxx; Mark Rutland > > <mark.rutland@xxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; Tan, Lean Sheng > > <sheng.tan@xxxxxxxxxxxxx>; lkml <linux-kernel@xxxxxxxxxxxxxxx>; Dhaval > > Sharma <dhaval@xxxxxxxxxxxx>; Brune, Maximilian > > <maximilian.brune@xxxxxxxxxxxxx>; Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx>; > > Dong, Guo <guo.dong@xxxxxxxxx>; Tom Rini <trini@xxxxxxxxxxxx>; ron minnich > > <rminnich@xxxxxxxxx>; Guo, Gua <gua.guo@xxxxxxxxx>; linux- > > acpi@xxxxxxxxxxxxxxx; U-Boot Mailing List <u-boot@xxxxxxxxxxxxx> > > Subject: Re: [PATCH v7 2/2] schemas: Add some common reserved-memory > > usages > > > > You are referring to a 2000 line patch so it is not 100% clear where to look tbh. > > > > > > On Tue, 21 Nov 2023 at 19:37, Chiu, Chasel <chasel.chiu@xxxxxxxxx> wrote: > > > > > > > > > In PR, UefiPayloadPkg/Library/FdtParserLib/FdtParserLib.c, line 268 is for > > related example code. > > > > > > > That refers to a 'memory-allocation' node, right? How does that relate to the > > 'reserved-memory' node? > > > > And crucially, how does this clarify in which way "runtime-code" and "runtime- > > data" reservations are being used? > > > > Since the very beginning of this discussion, I have been asking repeatedly for > > examples that describe the wider context in which these reservations are used. > > The "runtime" into runtime-code and runtime-data means that these regions have > > a special significance to the operating system, not just to the next bootloader > > stage. So I want to understand exactly why it is necessary to describe these > > regions in a way where the operating system might be expected to interpret this > > information and act upon it. > > > > > I think runtime code and data today are mainly for supporting UEFI runtime services - some BIOS functions for OS to utilize, OS may follow below ACPI spec to treat them as reserved range: > https://uefi.org/specs/ACPI/6.5/15_System_Address_Map_Interfaces.html#uefi-memory-types-and-mapping-to-acpi-address-range-types > > Like I mentioned earlier, that PR is still in early phase and has not reflected all the required changes yet, but the idea is to build gEfiMemoryTypeInformationGuid HOB from FDT reserved-memory nodes. > UEFI generic Payload has DxeMain integrated, however Memory Types are platform-specific, for example, some platforms may need bigger runtime memory for their implementation, that's why we want such FDT reserved-memory node to tell DxeMain. > > The Payload flow will be like this: > Payload creates built-in default MemoryTypes table -> > FDT reserved-memory node to override if required (this also ensures the same memory map cross boots so ACPI S4 works) -> > Build gEfiMemoryTypeInformationGuid HOB by "platfom specific" MemoryTypes Table -> > DxeMain/GCD to consume this MemoryTypes table and setup memory service -> > Install memory types table to UEFI system table.Configuration table... > > Note: if Payload built-in default MemoryTypes table works fine for the platform, then FDT reserved-memory node does not need to provide such 'usage' compatible strings. (optional) > This FDT node could allow flexibility/compatibility without rebuilding Payload binary. > > Not sure if I answered all your questions, please highlight which area you need more information. > The gEfiMemoryTypeInformationGuid HOB typically carries platform defaults, and the actual memory type information is kept in a non-volatile EFI variable, which gets updated when the memory usage changes. Is this different for UefiPayloadPkg? (For those among the cc'ees less versed in EFI/EDK2: when you get the 'config changed -rebooting' message from the boot firmware, it typically means that this memory type table has changed, and a reboot is necessary.) So the platform init needs to read this variable, or get the information in a different way. I assume it is the payload, not the platform init that updates the variable when necessary. This means the information flows from payload(n) to platform init(n+1), where n is a monotonic index tracking consecutive boots of the system. Can you explain how the DT fits into this? How are the runtime-code and runtime-data memory reservation nodes under /reserved-memory used to implement this information exchange between platform init and payload? And how do the HOB and the EFI variable fit into this picture?
