[Bug 2111715] Update Released

[Andreas Hasenack]

The verification of the Stable Release Update for ubuntu-release-
upgrader has completed successfully and the package is now being
released to -updates.  Subsequently, the Ubuntu Stable Release Updates
Team is being unsubscribed and will not receive messages about this bug
report.  In the event that you encounter a regression using the package
from -updates please report a new bug using ubuntu-bug and tag the bug
report regression-update so we can easily find any regressions.

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https://bugs.launchpad.net/bugs/2111715

Title:
  On RISC-V check if hardware is RVA23 capable

Status in ubuntu-release-upgrader package in Ubuntu:
  Fix Released
Status in ubuntu-release-upgrader source package in Noble:
  Won't Fix
Status in ubuntu-release-upgrader source package in Plucky:
  Fix Released
Status in ubuntu-release-upgrader source package in Questing:
  Fix Released

Bug description:
  [ Impact ]

  For Ubuntu 25.10 release we plan to raise the required RISC-V ISA
  profile family to RVA23.

  The ubuntu-release-upgrader should stop upgrades beyond Ubuntu 24.04
  on hardware that does not support the RVA23U64 profile. RVA23U64 [1]
  is the profile relevant for user space.

  As there is no upgrade path from Ubuntu 25.04 Plucky for RVA20
  systems, we should also stop upgrading these RISC-V systems from Noble
  to Plucky. Probably a warning is adequate here.

  The Noble entry is only a placeholder for the 24.04.3 milestone. All
  changes have to be done in the target releases (Questing, Noble).

  The Linux kernel exposes available extensions via /proc/cpuinfo field
  ISA and via the hwprobe system call [3]. Which extensions are exposed
  depends on the kernel revision. We are backporting a v6.14 kernel to
  Ubuntu 24.04. We have to restrict our check to those RVA23 extensions
  exposed by this kernel release.

  As the ubuntu-release-upgrader is implemented in Python we should use
  /proc/cpuinfo for the extension detection.

  [1]
  RVA23 Profiles, Version 1.0, 2024-10-17
  https://github.com/riscv/riscv-profiles/releases/download/rva23-rvb23-ratified/rva23-profile.pdf

  [2]
  RISC-V Linux User ABI
  https://docs.kernel.org/arch/riscv/uabi.html

  [3]
  RISC-V Hardware Probing Interface
  https://docs.kernel.org/arch/riscv/hwprobe.html

  [ Test Plan ]

  Test that Ubuntu 22.04 Jammy can be upgraded to Ubuntu 24.04 Noble on RVA20 hardware.
  Test that Ubuntu 24.04 Noble cannot be upgraded to Plucky or Questing on RVA20 hardware.
  Test that Ubuntu 25.04 Plucky cannot be upgraded to Questing on RVA20 hardware.
  Test that Ubuntu 24.04 Noble can be upgraded to Questing on a RVA23 virtual machine.
  Test that Ubuntu 24.04 Plucky can be upgraded to Questing on a RVA23 virtual machine.

  Test that Ubuntu 24.04 Plucky can be upgraded to Questing on an arm64
  virtual machine.

  QEMU 10.0 provides all RVA23U64 extensions.

  [ Where problems could occur ]

  If incorrectly implemented, the upgrader might not correctly identify
  RVA20 and RVA23 systems and therefore might stop or allow upgrades in
  the wrong case.

  [ Other Info ]

  n/a

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