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EBBR Notes 2025.04.23

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Vincent Stehlé edited this page Apr 23, 2025 · 4 revisions

Attendees

  • Heinrich Schuchardt (Canonical)
  • Jon Humphreys (Texas Instruments)
  • Vincent Stehlé (Arm)

Agenda

  • Pull #141: All runtime services optional after ExitBootServices()
  • Pull #142: Conditionally require SCMI 2.x, x >= 1 recommended

Notes

  • The two pull requests were discussed; some more investigations are needed to progress on the runtime services, and for the SCMI one some more comments are needed for clarity.

Raw notes

  • Pull #141: All runtime services optional after ExitBootServices()
    • Fear that other OSes need SetVirtualAddressMap() & ConvertPointer()
    • Linux has efi=novamap
    • Concerns for automotive about runtime services harming realtime and/or safety
    • Target of EBBR? Allow all OSes to boot?
    • We are stricter than UEFI 2.11 at this point
    • Do we pass SCT if we do not have those services?
    • Do we have enough to boot Windows today? Even with ACPI?
    • Check if BSD would be happy without SetVirtualAddressMap() & ConvertPointer()
      • Pine64 A64 could boot BSD; see list
      • Try on a mac :)
    • -> investigate a bit more
  • Pull #142: Conditionally require SCMI 2.x, x >= 1 recommended
    • Is it really desired to prevent 3.0?
    • Add a comment why it cannot be 3.x and must be 2.x
      • 3.x is guaranteed to be incompatible with 2.x, otherwise it should be called 2.y
      • Discussion between agent and server could start with 2.1, with negotiation to 3.x
      • Firmware implementing only 3.x would not be able to support old Linux of today, which support only 2.x
    • We can revisit when 3.0 is out
    • Given the complexity, capturing a nice requirement is of help to system implementers
    • -> polish a bit more
  • Birds of a feather session at Connect

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