[PATCH 0/4] riscv: Enable kexec handover and live update

[PATCH 0/4] riscv: Enable kexec handover and live update

[Chen Pei]

Host kernel updates in the cloud should not require draining the
machine: next to live migration to another host, replacing the kernel
in place while preserving selected workload state ("live update") is
what KHO/LUO were built for, and LUO's documentation names hypervisor
hosts as its primary use case. This series closes the gap for riscv64
and validates it with both upstream test runners.

KHO has been architecture independent since it was merged: the outgoing
kernel publishes the handover FDT and the scratch descriptor array in
the /chosen node of the DTB it builds for the incoming kernel, and the
incoming kernel collects both while scanning that node -- which is why
the arm64 integration (commit 274cdcb1c004) needed only three lines of
arch code.

RISC-V already walks those same generic paths (load_extra_segments() ->
of_kexec_alloc_and_setup_fdt(), parse_dtb() -> early_init_dt_scan()).
The one real blocker is ordering: setup_arch() runs early_ioremap_setup()
*after* parse_dtb(), so kho_populate()'s early_memremap() of the handover
FDT returns "offset + 0" -- NULL for a page aligned address -- and the
handover is dropped:

  KHO: setup: failed to memremap FDT (0x810bb000)
  KHO: disabling KHO revival

Patch 1 fixes that ordering, matching arm64/x86 and standing on its own
regardless of KHO. Patch 2 enables ARCH_SUPPORTS_KEXEC_HANDOVER as
"def_bool 64BIT && MMU" rather than arm64's "def_bool y":
ARCH_SUPPORTS_KEXEC_FILE is already 64BIT-only, and KEXEC_HANDOVER
selects CMA, which depends on MMU. Patches 3 and 4 teach the two
upstream vmtest runners about riscv64. LIVEUPDATE depends only on
KEXEC_HANDOVER, so patch 2 makes it selectable on riscv as well.

No DT schema changes are needed: linux,kho-fdt / linux,kho-scratch are
the properties arm64 introduced (commit 274cdcb1c004), and their
binding lives in the external dt-schema repository [1] rather than in
Documentation.

[1] https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/chosen.yaml

Test
----
Testing on qemu-system-riscv64 (virt, -cpu max, TCG); method and logs
under the --- of patches 3 and 4:
  - kho vmtest: "ok 1 KHO succeeded"
  - liveupdate vmtest, all four suites PASSED (simple, multi-session,
    500 files, 2000 sessions)
  - riscv defconfig with and without CONFIG_KEXEC_HANDOVER both boot to
    userspace unchanged; builds: riscv defconfig (+KHO), rv32_defconfig,
    arm64, x86_64

Additionally, a workload-continuity test was run on the same setup,
outside the selftests: a counter process was snapshot with criu 4.3,
the dump was carried across the kexec in an LUO-preserved memfd, and
criu restored it in the new kernel. The process resumed with the same
PID and open log file and kept counting from where it was dumped
(500006 -> 500007, no lost or duplicated ticks).

Chen Pei (4):
  riscv: Call early_ioremap_setup() before parsing the DTB
  riscv: Add support for kexec handover (KHO)
  selftests: kho: Add riscv support
  selftests: liveupdate: Add riscv support

 arch/riscv/Kconfig                                | 3 +++
 arch/riscv/kernel/setup.c                         | 2 +-
 tools/testing/selftests/kho/riscv.conf            | 9 +++++++++
 tools/testing/selftests/kho/vmtest.sh             | 3 ++-
 tools/testing/selftests/liveupdate/config.riscv64 | 3 +++
 tools/testing/selftests/liveupdate/run-vmtests.sh | 2 +-
 tools/testing/selftests/liveupdate/vmtest.sh      | 8 +++++++-
 7 files changed, 26 insertions(+), 4 deletions(-)
 create mode 100644 tools/testing/selftests/kho/riscv.conf
 create mode 100644 tools/testing/selftests/liveupdate/config.riscv64

-- 
2.50.1

[PATCH 1/4] riscv: Call early_ioremap_setup() before parsing the DTB

[Chen Pei]

early_ioremap_setup() fills in the slot_virt[] array whose entries the
return value of early_ioremap()/early_memremap() is composed from.  On
RISC-V it ran after parse_dtb(), so an early_memremap() reached from
the device tree scan returned "offset + 0" -- NULL for a page aligned
address -- and the caller could only report a mapping failure.  This
stayed latent because nothing reached from parse_dtb() asked for an
early mapping before; the DT based kexec handover parsing is the first
such caller, as kho_populate() maps the handover FDT and the scratch
descriptor array with early_memremap().

Move the call to the top of setup_arch(), which is how arm64 and x86
already order it (early_fixmap_init()/early_ioremap_init() before
setup_machine_fdt()/parse_setup_data()).  The BTMAP window is mapped
into early_pg_dir by setup_vm(), and RISC-V neither calls
early_ioremap_reset() nor defines __late_set_fixmap(), so the virtual
addresses stay identical across the switch to the final page tables
and nothing else in setup_arch() depends on the previous ordering.

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
---
 arch/riscv/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index d79f99b86033..45e2ef9d32fa 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -308,12 +308,12 @@ extern void __init init_rt_signal_env(void);
 
 void __init setup_arch(char **cmdline_p)
 {
+	early_ioremap_setup();
 	parse_dtb();
 	setup_initial_init_mm(_stext, _etext, _edata, _end);
 
 	*cmdline_p = boot_command_line;
 
-	early_ioremap_setup();
 	sbi_init();
 	jump_label_init();
 	parse_early_param();
-- 
2.50.1

[PATCH 2/4] riscv: Add support for kexec handover (KHO)

[Chen Pei]

KHO is architecture independent: the outgoing kernel publishes the
handover FDT and the scratch descriptor array in the /chosen node of
the DTB it builds for the incoming kernel (kho_add_chosen(), reached
from of_kexec_alloc_and_setup_fdt()), and the incoming kernel picks
both up while scanning that node (early_init_dt_check_kho() ->
kho_populate()).

RISC-V already builds that DTB in load_extra_segments() and passes it
to the incoming kernel in a1, so only the architecture symbol is
missing.  Depend on 64BIT to match ARCH_SUPPORTS_KEXEC_FILE, and on
MMU because KEXEC_HANDOVER selects CMA, which depends on MMU.

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
---
 arch/riscv/Kconfig | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 5874ca30f4f6..4f7d2f3f80b1 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -1125,6 +1125,9 @@ config ARCH_SELECTS_KEXEC_FILE
 config ARCH_SUPPORTS_KEXEC_PURGATORY
 	def_bool ARCH_SUPPORTS_KEXEC_FILE
 
+config ARCH_SUPPORTS_KEXEC_HANDOVER
+	def_bool 64BIT && MMU
+
 config ARCH_SUPPORTS_CRASH_DUMP
 	def_bool y
 
-- 
2.50.1

[PATCH 3/4] selftests: kho: Add riscv support

[Chen Pei]

Teach the KHO vmtest runner about riscv64: map the target to ARCH
riscv and describe the QEMU virt machine, the kernel image and its
console -- a 16550A port probed from the device tree on virt, hence
the SERIAL_8250{,_CONSOLE} and SERIAL_OF_PLATFORM symbols.  Also
select CONFIG_SPARSEMEM_MANUAL: the runner requires
CONFIG_DEFERRED_STRUCT_PAGE_INIT, which depends on SPARSEMEM, while
riscv falls back to FLATMEM (no ARCH_SPARSEMEM_DEFAULT), so without
it the test would just be skipped.

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
---
Test: qemu-system-riscv64 (virt, -cpu max, TCG), in-tree runner
"tools/testing/selftests/kho/vmtest.sh -t riscv64" (boots the Image
and kexec'es into the same Image).

  KHO: found kexec handover data.
  KHO: exec from: 7.3.0-rc7-00108-gc6e90ee4ccbb (count 1)
  test_kho: KHO restore succeeded
  ok 1 KHO succeeded
  # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

 tools/testing/selftests/kho/riscv.conf | 9 +++++++++
 tools/testing/selftests/kho/vmtest.sh  | 3 ++-
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/kho/riscv.conf

diff --git a/tools/testing/selftests/kho/riscv.conf b/tools/testing/selftests/kho/riscv.conf
new file mode 100644
index 000000000000..ec2a46cd45d5
--- /dev/null
+++ b/tools/testing/selftests/kho/riscv.conf
@@ -0,0 +1,9 @@
+QEMU_CMD="qemu-system-riscv64 -M virt -cpu max"
+QEMU_KCONFIG="
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SERIAL_OF_PLATFORM=y
+CONFIG_SPARSEMEM_MANUAL=y
+"
+KERNEL_IMAGE="Image"
+KERNEL_CMDLINE="console=ttyS0"
diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh
index 0014bd76e88d..325af59f653a 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, riscv64
 	-h)	display this help
 EOF
 }
@@ -127,6 +127,7 @@ function target_to_arch() {
 	case $target in
 	     aarch64) echo "arm64" ;;
 	     x86_64) echo "x86" ;;
+	     riscv64) echo "riscv" ;;
 	     *) skip "architecture $target is not supported"
 	esac
 }
-- 
2.50.1

[PATCH 4/4] selftests: liveupdate: Add riscv support

[Chen Pei]

Teach the live update vmtest runner about riscv64: map the target to ARCH
riscv, describe the QEMU virt machine, the kernel image and its console,
and add the arch config fragment holding the three symbols needed to get
a console on the virt machine's 16550A port.

KHO is the only dependency of LIVEUPDATE (kernel/liveupdate/Kconfig), so
now that riscv has KHO the LUO tests only need the runner to stop
rejecting the architecture.

Add riscv64 to the CROSS_COMPILE auto-detection list and to the target
list of the batch runner as well, matching the existing aarch64/x86_64
entries.

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
---
Test: qemu-system-riscv64 (virt, -cpu max, -m 1G, -smp 2, TCG), in-tree
runner "tools/testing/selftests/liveupdate/vmtest.sh -t riscv64 -T <suite>",
all four suites:

  luo_kexec_simple:    SIMPLE KEXEC TEST PASSED
  luo_multi_session:   MULTI-SESSION KEXEC TEST PASSED
  luo_stress_files:    MANY-FILES KEXEC TEST PASSED (500 files)
  luo_stress_sessions: MANY-SESSIONS KEXEC TEST PASSED (2000 sessions)

The simple suite's serial log shows the full handover round trip:

  KHO: found kexec handover data.
  luo: Retrieved live update data, liveupdate number: 1
  # [STAGE 2] Test data verified successfully.
  --- SIMPLE KEXEC TEST PASSED ---

 tools/testing/selftests/liveupdate/config.riscv64 | 3 +++
 tools/testing/selftests/liveupdate/run-vmtests.sh | 2 +-
 tools/testing/selftests/liveupdate/vmtest.sh      | 8 +++++++-
 3 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/liveupdate/config.riscv64

diff --git a/tools/testing/selftests/liveupdate/config.riscv64 b/tools/testing/selftests/liveupdate/config.riscv64
new file mode 100644
index 000000000000..edbc551199b0
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/config.riscv64
@@ -0,0 +1,3 @@
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SERIAL_OF_PLATFORM=y
diff --git a/tools/testing/selftests/liveupdate/run-vmtests.sh b/tools/testing/selftests/liveupdate/run-vmtests.sh
index d656ce58c5a7..2e3f5f6f96b3 100755
--- a/tools/testing/selftests/liveupdate/run-vmtests.sh
+++ b/tools/testing/selftests/liveupdate/run-vmtests.sh
@@ -4,7 +4,7 @@
 SCRIPT_DIR=$(dirname "$(realpath "$0")")
 TEST_RUNNER="$SCRIPT_DIR/vmtest.sh"
 
-TARGETS=("x86_64" "aarch64")
+TARGETS=("x86_64" "aarch64" "riscv64")
 
 GREEN='\033[0;32m'
 RED='\033[0;31m'
diff --git a/tools/testing/selftests/liveupdate/vmtest.sh b/tools/testing/selftests/liveupdate/vmtest.sh
index 64fd2ab55b76..ee554d889e1b 100755
--- a/tools/testing/selftests/liveupdate/vmtest.sh
+++ b/tools/testing/selftests/liveupdate/vmtest.sh
@@ -25,6 +25,10 @@ function get_arch_conf() {
 		QEMU_CMD="qemu-system-x86_64"
 		KERNEL_IMAGE="bzImage"
 		KERNEL_CMDLINE="console=ttyS0"
+	elif [[ "$arch" == "riscv" ]]; then
+		QEMU_CMD="qemu-system-riscv64 -M virt -cpu max"
+		KERNEL_IMAGE="Image"
+		KERNEL_CMDLINE="console=ttyS0"
 	else
 		echo "Unsupported architecture: $arch"
 		exit 1
@@ -37,7 +41,7 @@ $0 [-d build_dir] [-j jobs] [-t target_arch] [-T test_name] [-w workspace_dir] [
 Options:
 	-d)	path to the kernel build directory (default: .luo_test_build.<arch>)
 	-j)	number of jobs for compilation
-	-t)	run test for target_arch (aarch64, x86_64)
+	-t)	run test for target_arch (aarch64, x86_64, riscv64)
 	-T)	test name to run (default: luo_kexec_simple)
 	-w)	custom workspace directory (default: creates temp dir)
 	-k)	keep workspace directory after successful test
@@ -87,6 +91,7 @@ function detect_cross_compile() {
 	case "$target" in
 		aarch64) candidate="aarch64-linux-gnu-" ;;
 		x86_64)  candidate="x86_64-linux-gnu-" ;;
+		riscv64) candidate="riscv64-linux-gnu-" ;;
 		*)       skip "Auto-detection for target '$target' not supported. Please set CROSS_COMPILE manually." ;;
 	esac
 
@@ -194,6 +199,7 @@ function target_to_arch() {
 	case $target in
 	     aarch64) echo "arm64" ;;
 	     x86_64) echo "x86" ;;
+	     riscv64) echo "riscv" ;;
 	     *) skip "architecture $target is not supported"
 	esac
 }
-- 
2.50.1