[PATCH v3 0/3] LoongArch: add KHO support and selftests

[PATCH v3 0/3] LoongArch: add KHO support and selftests

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

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

KHO passes metadata (the KHO state FDT and scratch area addresses) to the
second kernel via the FDT /chosen node, using the linux,kho-fdt and
linux,kho-scratch properties that drivers/of/kexec.c:kho_add_chosen()
writes and drivers/of/fdt.c:early_init_dt_check_kho() reads.

KHO support (patches 1-2):

Patch 1 adds KHO support for FDT-based systems (initial_boot_params !=
NULL, e.g. QEMU virt without OVMF).  kho_load_fdt() copies the running
kernel's FDT, appends linux,kho-fdt and linux,kho-scratch to /chosen,
and loads the result as a kexec segment.  machine_kexec() updates the
DEVICE_TREE_GUID entry in the EFI config table to point to this segment
so the second kernel's fdt_setup() can find and parse it.

Patch 2 adds KHO support for ACPI-only systems (initial_boot_params ==
NULL, e.g. LoongArch servers with UEFI or QEMU with OVMF).  Because no
system FDT is available, kho_load_fdt() builds a minimal FDT from
scratch containing only /chosen with the two KHO properties.  Since
DEVICE_TREE_GUID is absent from the EFI config table on ACPI-only
systems, a new extended config table is built with the entry appended
and loaded as a kexec segment; machine_kexec() switches st->tables to
point to it before jumping.  The second kernel's fdt_setup() calls
efi_fdt_pointer() to detect the KHO FDT and passes it to
early_init_dt_check_kho().

Selftest support (patch 3):

Patch 3 adds loongarch.conf and extends vmtest.sh to recognise loongarch64
as a build target.  The LoongArch virt machine is FDT-only (no ACPI), so
'earlycon' must appear on the kernel cmdline or the console UART is never
discovered.  PS/2 input devices are disabled since QEMU's LoongArch virt
machine has no i8042 controller; the fallback port probe hits a page fault
and panics before reaching userspace.  QEMU provides no EFI runtime
services on LoongArch, so machine_restart() falls through to an infinite
idle loop after kexec; QEMU_TIMEOUT=120 in loongarch.conf lets timeout(1)
terminate QEMU once the time limit is reached.

Changes in v3:
- Merge selftest patches 3 and 4 from v2 into a single patch
- Replace QEMU_NEEDS_KILL/background kill loop with QEMU_TIMEOUT/timeout(1);
  the timeout value is set per-arch in the conf file.

George Guo (3):
  LoongArch: kexec: add KHO support for FDT-based systems
  LoongArch: kexec: add KHO support for ACPI-only systems
  selftests/kho: add LoongArch vmtest support

 arch/loongarch/Kconfig                     |   3 +
 arch/loongarch/include/asm/kexec.h         |   7 +
 arch/loongarch/kernel/machine_kexec.c      |  38 +++
 arch/loongarch/kernel/machine_kexec_file.c | 256 +++++++++++++++++++++
 arch/loongarch/kernel/setup.c              |  21 +-
 tools/testing/selftests/kho/loongarch.conf |  13 ++
 tools/testing/selftests/kho/vmtest.sh      |  23 +-
 7 files changed, 353 insertions(+), 8 deletions(-)
 create mode 100644 tools/testing/selftests/kho/loongarch.conf

--
2.25.1

[PATCH v3 3/3] selftests/kho: add LoongArch vmtest support

[George Guo]

From: George Guo <guodongtai@kylinos.cn>

Add loongarch.conf to configure QEMU's LoongArch virt machine with a
la464 CPU, enable the 8250 serial console, and set the kernel image
to vmlinux.efi.  Extend vmtest.sh to recognise loongarch64 as a
supported target and map it to the 'loongarch' kernel arch name.

QEMU's LoongArch virt machine provides no ACPI tables and relies on
FDT to describe hardware.  Without 'earlycon' on the kernel command
line, the FDT is not scanned for a console UART, no output reaches
the console, and vmtest.sh's console log stays empty causing the test
to always fail.  Add 'earlycon' to KERNEL_CMDLINE in loongarch.conf.

QEMU's LoongArch virt machine has no i8042 PS/2 controller.  When PNP
detection finds nothing, i8042_init() falls back to probing the ports
directly.  On LoongArch the I/O ports are memory-mapped, and the i8042
port addresses are not backed by any device on the virt machine, so
i8042_flush() takes a page fault and the kernel panics:

  i8042: PNP: No PS/2 controller found.
  i8042: Probing ports directly.
  CPU 0 Unable to handle kernel paging request at virtual address ffff800000008064
  ERA: i8042_flush+0x50/0x198
   RA: i8042_init+0x2a8/0x35c
  Kernel panic - not syncing: Attempted to kill init!

Disable SERIO_I8042 and its dependents (KEYBOARD_ATKBD, MOUSE_PS2) in
the QEMU_KCONFIG fragment to prevent the driver from being built.
All three options are scoped to loongarch.conf; no other architecture
is affected.

QEMU provides no EFI runtime services on LoongArch, so machine_restart()
falls through to an infinite idle loop after kexec.  Set QEMU_TIMEOUT=120
in loongarch.conf so vmtest.sh wraps the QEMU invocation with timeout(1),
which terminates QEMU after 120 seconds if it does not exit on its own.
Architectures that do not set QEMU_TIMEOUT are unaffected.

Co-developed-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: Kexin Liu <liukexin@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
---
 tools/testing/selftests/kho/loongarch.conf | 13 ++++++++++++
 tools/testing/selftests/kho/vmtest.sh      | 23 +++++++++++++++-------
 2 files changed, 29 insertions(+), 7 deletions(-)
 create mode 100644 tools/testing/selftests/kho/loongarch.conf

diff --git a/tools/testing/selftests/kho/loongarch.conf b/tools/testing/selftests/kho/loongarch.conf
new file mode 100644
index 000000000000..68727654578d
--- /dev/null
+++ b/tools/testing/selftests/kho/loongarch.conf
@@ -0,0 +1,13 @@
+QEMU_CMD="qemu-system-loongarch64 -M virt -cpu la464"
+QEMU_KCONFIG="
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+# CONFIG_KEYBOARD_ATKBD is not set
+# CONFIG_MOUSE_PS2 is not set
+# CONFIG_SERIO_I8042 is not set
+"
+KERNEL_IMAGE="vmlinux.efi"
+KERNEL_CMDLINE="console=ttyS0 earlycon"
+# QEMU never exits after kexec on LoongArch (no EFI runtime services);
+# give the test a fixed time limit and let timeout(1) terminate QEMU.
+QEMU_TIMEOUT=120
diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh
index 49fdac8e8b15..918698b6dd2a 100755
--- a/tools/testing/selftests/kho/vmtest.sh
+++ b/tools/testing/selftests/kho/vmtest.sh
@@ -21,7 +21,7 @@ Options:
 	-d)	path to the kernel build directory
 	-j)	number of jobs for compilation, similar to -j in make
 	-t)	run test for target_arch, requires CROSS_COMPILE set
-		supported targets: aarch64, x86_64
+		supported targets: aarch64, x86_64, loongarch64
 	-h)	display this help
 EOF
 }
@@ -107,12 +107,20 @@ function run_qemu() {
 
 	cmdline="$cmdline kho=on panic=-1"
 
-	$qemu_cmd -m 1G -smp 2 -no-reboot -nographic -nodefaults \
-		  -accel kvm -accel hvf -accel tcg  \
-		  -serial file:"$serial" \
-		  -append "$cmdline" \
-		  -kernel "$kernel" \
-		  -initrd "$initrd"
+	local qemu_args=(
+		-m 1G -smp 2 -no-reboot -nographic -nodefaults
+		-accel kvm -accel hvf -accel tcg
+		-serial file:"$serial"
+		-append "$cmdline"
+		-kernel "$kernel"
+		-initrd "$initrd"
+	)
+
+	if [[ -n "${QEMU_TIMEOUT:-}" ]]; then
+		timeout "$QEMU_TIMEOUT" $qemu_cmd "${qemu_args[@]}" || true
+	else
+		$qemu_cmd "${qemu_args[@]}"
+	fi
 
 	grep "KHO restore succeeded" "$serial" &> /dev/null || fail "KHO failed"
 }
@@ -123,6 +131,7 @@ function target_to_arch() {
 	case $target in
 	     aarch64) echo "arm64" ;;
 	     x86_64) echo "x86" ;;
+	     loongarch64) echo "loongarch" ;;
 	     *) skip "architecture $target is not supported"
 	esac
 }
-- 
2.25.1

Re: [PATCH v3 0/3] LoongArch: add KHO support and selftests

[George Guo]

Hi Mike, Huacai,

Gentle ping on this v3. In the v2 review you mentioned you'd wait for
v3 for a more detailed look -- v3 addresses both points (folded the two
selftest patches into one, and replaced the LoongArch-specific kill
loop with timeout(1), with the timeout value set per-arch in the conf).

No rush, just making sure it didn't slip through the cracks. Happy to
spin a rebase if it's gone stale.

Thanks!

--
George

Re: [PATCH v3 0/3] LoongArch: add KHO support and selftests

[Pratyush Yadav]

On Tue, Jun 09 2026, George Guo wrote:

> Hi Mike, Huacai,
>
> Gentle ping on this v3. In the v2 review you mentioned you'd wait for
> v3 for a more detailed look -- v3 addresses both points (folded the two
> selftest patches into one, and replaced the LoongArch-specific kill
> loop with timeout(1), with the timeout value set per-arch in the conf).
>
> No rush, just making sure it didn't slip through the cracks. Happy to
> spin a rebase if it's gone stale.

It is on my review list, and I hope to get to it soon. But no promises
unfortunately.

-- 
Regards,
Pratyush Yadav