[PATCH 0/7] LoongArch: add KHO support and selftests

[George Guo <dongtai.guo@linux.dev>]

From: George Guo <guodongtai@kylinos.cn>>

This series adds Kexec Handover (KHO) support for LoongArch64 and
extends the KHO selftest infrastructure to run on LoongArch under QEMU.

KHO support (patches 1-2)
--------------------------
Patch 1 wires up the three pieces needed for KHO on LoongArch:
 - Kconfig: select ARCH_SUPPORTS_KEXEC_HANDOVER for 64BIT
 - machine_kexec_file: call cmdline_add_kho() to pass the KHO FDT and
   scratch buffer addresses via "kho_handover=" on the kernel cmdline
 - setup: parse "kho_handover=" early and call kho_populate()

Patch 2 fixes a duplicate-parameter bug when kexec is invoked with
--reuse-cmdline: the running kernel's cmdline already contains a stale
kho_handover= from the previous load.  load_other_segments() prepends a
fresh entry but appends the original cmdline verbatim, so early_param()
calls kho_populate() twice and the second call overwrites the first with
a stale FDT pointer, panicking early in mm_core_init().

Bug fixes (patches 3-4)
------------------------
Patch 3 fixes a build failure with CONFIG_KFENCE=y: virt_to_phys() and
phys_to_virt() in asm/io.h expand to use offset_in_page() and
page_address(), which require <linux/mm.h> that was not included.

Patch 4 moves KEXEC_CONTROL_CODE from 0x100000 to 0x180000.  QEMU
places its machine FDT at 0x100000 when booting with '-kernel'; the
previous placement silently overwrote the FDT with the relocation
trampoline, breaking earlycon in the kexec'd kernel.

Selftest support (patches 5-7)
-------------------------------
Patch 5 adds loongarch.conf and extends vmtest.sh to recognise
loongarch64 as a build target.  QEMU's LoongArch virt machine is
FDT-only (no ACPI), so 'earlycon' must appear on the kernel cmdline or
the console UART is never discovered and the test log stays empty.

Patch 6 disables SERIO_I8042 and its dependents in the QEMU_KCONFIG
fragment.  QEMU's LoongArch virt machine has no i8042 controller; the
fallback port probe hits a page fault on the memory-mapped I/O range and
panics before reaching userspace.

Patch 7 polls the serial output for the test verdict and kills QEMU once
it appears.  QEMU provides no EFI runtime services on LoongArch, so
machine_restart() falls through to an infinite idle loop and QEMU never
exits after kexec.


George Guo (7):
  LoongArch: Add KHO basic support
  LoongArch: kho: strip stale kho_handover= from reused cmdline
  LoongArch: Add missing linux/mm.h include in asm/io.h
  LoongArch: kexec: avoid overwriting QEMU's machine FDT at 0x100000
  selftests/kho: add LoongArch vmtest support
  selftests/kho: LoongArch: disable PS/2 input devices for QEMU virt
  selftests/kho: handle QEMU not exiting after kexec on LoongArch

 arch/loongarch/Kconfig                     |  3 ++
 arch/loongarch/include/asm/io.h            |  1 +
 arch/loongarch/kernel/machine_kexec.c      |  9 +++-
 arch/loongarch/kernel/machine_kexec_file.c | 57 ++++++++++++++++++++++
 arch/loongarch/kernel/setup.c              | 27 ++++++++++
 tools/testing/selftests/kho/loongarch.conf | 10 ++++
 tools/testing/selftests/kho/vmtest.sh      | 38 ++++++++++++---
 7 files changed, 135 insertions(+), 10 deletions(-)
 create mode 100644 tools/testing/selftests/kho/loongarch.conf

-- 
2.25.1