[PATCH v4 0/2] Add QEMU virt-ctrl driver and update m68k virt

Kuan-Wei Chiu
2026-04-12T21:20:08Z

Introduce a generic platform driver for the QEMU 'virt-ctrl' device [1]
and transitions the m68k 'virt' machine to use it, replacing
architecture-specific hooks.

The new driver ('qemu-virt-ctrl') registers a restart handler and
populates the global 'pm_power_off' callback.

On the m68k side, the platform initialization is updated to register
the 'qemu-virt-ctrl' platform device. Additionally, the 'mach_reset'
hook is bridged to 'do_kernel_restart()' to ensure the kernel's restart
handler chain is correctly invoked.

Verified on QEMU m68k virt. Both system reset and power-off were
confirmed functional by invoking 'reboot(LINUX_REBOOT_CMD_RESTART)',
'reboot(LINUX_REBOOT_CMD_POWER_OFF)', and
'reboot(LINUX_REBOOT_CMD_HALT)' from userspace.

Link: https://gitlab.com/qemu-project/qemu/-/blob/v10.2.0/hw/misc/virt_ctrl.c [1]
---
Changes in v4:
- Fix sparse warning caught by kernel test robot.
- Pass the struct qemu_virt_ctrl context to sys-off handlers instead of
the __iomem pointer.

Changes in v3:
- Add a reboot notifier in the driver to handle LINUX_REBOOT_CMD_HALT.
- Handle native endianness in the driver instead of hardcoding
big-endian I/O writes.
- Select POWER_RESET and POWER_RESET_QEMU_VIRT_CTRL in m68k
Kconfig.machine.

Changes in v2:
- Use devm_register_sys_off_handler() instead of register_restart_handler()
and global pm_power_off.
- Switch Kconfig to tristate to support modular build.
- Add .id_table to platform_driver and use MODULE_DEVICE_TABLE() to correct
module auto-loading.

v2: https://lore.kernel.org/lkml/20260203170824.2968045-1-visitorckw@gmail.com/
v1: https://lore.kernel.org/lkml/20260112182258.1851769-1-visitorckw@gmail.com/

Kuan-Wei Chiu (2):
power: reset: Add QEMU virt-ctrl driver
m68k: virt: Switch to qemu-virt-ctrl driver

MAINTAINERS | 6 ++
arch/m68k/Kconfig.machine | 2 +
arch/m68k/virt/config.c | 42 +--------
arch/m68k/virt/platform.c | 20 ++++-
drivers/power/reset/Kconfig | 10 +++
drivers/power/reset/Makefile | 1 +
drivers/power/reset/qemu-virt-ctrl.c | 122 +++++++++++++++++++++++++++
7 files changed, 159 insertions(+), 44 deletions(-)
create mode 100644 drivers/power/reset/qemu-virt-ctrl.c

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2.53.0.1213.gd9a14994de-goog