[PATCH v6 0/8] LoongArch: Add KHO support and selftests

[George Guo]

From: George Guo <guodongtai@xxxxxxxxxx>

This series enables Kexec HandOver (KHO) on 64-bit LoongArch and adds
LoongArch to the KHO and liveupdate QEMU selftests.

KHO has to give the next kernel two addresses: the KHO FDT and the
bootmem area list. arm64 and riscv put them under /chosen in the boot
FDT, and x86 puts them in setup_data. LoongArch systems that boot with
EFI and ACPI have no boot FDT, so this series passes the addresses in a
Linux EFI configuration table:

  - On a cold boot, the LoongArch EFI stub installs the table, zeroed.
    Kernels started by kexec are given the same EFI system table, so
    they find the same table.
  - In early boot, the kernel reserves the table and calls
    kho_populate() if the table holds KHO state.
  - Just before kexec, the kernel writes the KHO state of the image it
    is about to run, or zeroes the table if that image has none, for
    example a crash kernel.

A kernel started by kexec from a kernel that did not install the table
has no table and cannot pass KHO state on, so LoongArch turns KHO off at
boot in that case.

Patch 1 adds the table, and patch 2 writes it at kexec time. Patch 3
fixes a kho_block.c build failure with CONFIG_KFENCE=y on LoongArch.
Patch 4 adds kho_disable(). Patch 5 lets the LoongArch memblock
arrays grow, which restoring many preserved regions needs, and patch 6
enables KHO on LoongArch. Patches 7 and 8 add LoongArch to the KHO and
liveupdate vmtests.

The series is based on liveupdate-7.4 and depends on "liveupdate: kho:
calculate per-node bootmem sizes before allocating any" [1]. Without
it, the KHO vmtest fails on a 1 GiB LoongArch guest because KHO cannot
reserve its bootmem areas.

Tested in QEMU: the KHO vmtest passes on LoongArch with both
CONFIG_NUMA=n and CONFIG_NUMA=y, and run-vmtests.sh passes all four
liveupdate tests on x86_64, aarch64 and loongarch64.

Changes since v5:
  - Drop CONFIG_EFI_KHO. Only the LoongArch stub installs the table,
    from efi_boot_kernel(). The other code is built with CONFIG_EFI and
    does nothing when there is no table (Pratyush).
  - efi_kho_update() returns 0 when there is no table, so kexec on other
    architectures is not affected.
  - Warn if the table cannot be mapped in early boot (Pratyush).
  - Document each member of struct linux_efi_kho_data and drop __packed
    (Pratyush).
  - Rename efi_kho_table_phys to efi_kho, mark it __initdata, and join
    wrapped lines (Huacai).
  - Rename kho_sync_channel() to kho_update_efi_table(), and stop
    calling the table a "channel" or "transport" (Mike, Pratyush).
  - New patch 4: turn KHO off at boot on LoongArch when the table is
    missing.
  - New patch 5: allow the memblock arrays to resize on LoongArch. The
    liveupdate luo_stress_files test overflowed the reserved array in
    the next kernel when CONFIG_SMP was not set.
  - New patch 8: add LoongArch to the liveupdate vmtest.
  - Rename scratch to bootmem, following Pratyush's rename series.
  - Drop the luo_session history from patch 3's commit message
    (Pratyush).
  - Capitalize the subjects and use the kho: prefix (Huacai).
  - Rewrite the cover letter and commit messages (Mike, Pratyush).
  - Rebase onto liveupdate-7.4.
  - No Assisted-by tags, although my v5 reply said patches written with
    LLM help would carry one: the Assisted-by references have since been
    removed from the documentation in mainline.

[1] https://lore.kernel.org/all/20261029103425.14689-1-dongtai.guo@xxxxxxxxx/

v5: https://lore.kernel.org/loongarch/20260904100852.26006-1-dongtai.guo@xxxxxxxxx/
v4: https://lore.kernel.org/loongarch/20260807103714.33074-1-dongtai.guo@xxxxxxxxx/

George Guo (8):
  efi: Pass KHO state to the next kernel in a configuration table
  kho: Write KHO state to the EFI table at kexec time
  kho: Include linux/mm.h in kho_block.c
  kho: Add kho_disable()
  LoongArch: Allow memblock arrays to resize
  LoongArch: Enable kexec handover (KHO)
  selftests/kho: Add LoongArch vmtest support
  selftests/liveupdate: Add LoongArch vmtest support

 arch/loongarch/Kconfig                        |  3 +
 arch/loongarch/kernel/setup.c                 | 19 ++++++
 drivers/firmware/efi/efi.c                    | 68 +++++++++++++++++++
 drivers/firmware/efi/libstub/efi-stub.c       | 22 ++++++
 drivers/firmware/efi/libstub/efistub.h        |  2 +
 drivers/firmware/efi/libstub/loongarch.c      |  2 +
 include/linux/efi.h                           | 40 +++++++++++
 include/linux/kexec_handover.h                |  3 +
 kernel/crash_core.c                           |  6 ++
 kernel/kexec_core.c                           |  5 ++
 kernel/kexec_internal.h                       |  8 +++
 kernel/liveupdate/kexec_handover.c            | 35 ++++++++++
 kernel/liveupdate/kho_block.c                 |  1 +
 tools/testing/selftests/kho/loongarch.conf    | 11 +++
 tools/testing/selftests/kho/vmtest.sh         |  3 +-
 .../selftests/liveupdate/config.loongarch64   |  5 ++
 .../selftests/liveupdate/run-vmtests.sh       |  4 +-
 tools/testing/selftests/liveupdate/vmtest.sh  | 14 +++-
 18 files changed, 247 insertions(+), 4 deletions(-)
 create mode 100644 tools/testing/selftests/kho/loongarch.conf
 create mode 100644 tools/testing/selftests/liveupdate/config.loongarch64


base-commit: 9a6a70aefe77f6fb9ff2b3037dcf87f6dff65c8c
prerequisite-patch-id: 433e6f8fdec5151f12221a0a34f8fb111b95bb46
-- 
2.53.0