* [PATCH v4 1/2] power: reset: Add QEMU virt-ctrl driver
2026-04-12 21:19 [PATCH v4 0/2] Add QEMU virt-ctrl driver and update m68k virt Kuan-Wei Chiu
@ 2026-04-12 21:19 ` Kuan-Wei Chiu
2026-04-12 21:19 ` [PATCH v4 2/2] m68k: virt: Switch to qemu-virt-ctrl driver Kuan-Wei Chiu
2026-04-13 10:19 ` [PATCH v4 0/2] Add QEMU virt-ctrl driver and update m68k virt Geert Uytterhoeven
2 siblings, 0 replies; 4+ messages in thread
From: Kuan-Wei Chiu @ 2026-04-12 21:19 UTC (permalink / raw)
To: geert, sre
Cc: jserv, eleanor15x, daniel, laurent, linux-kernel, linux-m68k,
linux-pm, Kuan-Wei Chiu, Sebastian Reichel
Add a new driver for the 'virt-ctrl' device found on QEMU virt machines
(e.g. m68k). This device provides a simple interface for system reset
and power off [1].
This driver utilizes the modern system-off API to register callbacks
for both system restart and power off. It also registers a reboot
notifier to catch SYS_HALT events, ensuring that LINUX_REBOOT_CMD_HALT
is properly handled. It is designed to be generic and can be reused by
other architectures utilizing this QEMU device.
Link: https://gitlab.com/qemu-project/qemu/-/blob/v10.2.0/hw/misc/virt_ctrl.c [1]
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
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.
MAINTAINERS | 6 ++
drivers/power/reset/Kconfig | 10 +++
drivers/power/reset/Makefile | 1 +
drivers/power/reset/qemu-virt-ctrl.c | 122 +++++++++++++++++++++++++++
4 files changed, 139 insertions(+)
create mode 100644 drivers/power/reset/qemu-virt-ctrl.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 55af015174a5..aa9eb8540637 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -21441,6 +21441,12 @@ S: Maintained
F: drivers/firmware/qemu_fw_cfg.c
F: include/uapi/linux/qemu_fw_cfg.h
+QEMU VIRT MACHINE SYSTEM CONTROLLER DRIVER
+M: Kuan-Wei Chiu <visitorckw@gmail.com>
+L: linux-pm@vger.kernel.org
+S: Maintained
+F: drivers/power/reset/qemu-virt-ctrl.c
+
QLOGIC QL41xxx FCOE DRIVER
M: Saurav Kashyap <skashyap@marvell.com>
M: Javed Hasan <jhasan@marvell.com>
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index f6c1bcbb57de..99e3334726a5 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -354,4 +354,14 @@ config POWER_MLXBF
help
This driver supports reset or low power mode handling for Mellanox BlueField.
+config POWER_RESET_QEMU_VIRT_CTRL
+ tristate "QEMU Virt Machine System Controller"
+ depends on HAS_IOMEM
+ help
+ This driver supports the system reset and power off functionality
+ provided by the QEMU 'virt-ctrl' device.
+
+ Say Y here if you are running Linux on a QEMU virtual machine that
+ provides this controller, such as the m68k virt machine.
+
endif
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index 0e4ae6f6b5c5..d7ae97241a83 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -41,3 +41,4 @@ obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o
obj-$(CONFIG_POWER_RESET_SC27XX) += sc27xx-poweroff.o
obj-$(CONFIG_NVMEM_REBOOT_MODE) += nvmem-reboot-mode.o
obj-$(CONFIG_POWER_MLXBF) += pwr-mlxbf.o
+obj-$(CONFIG_POWER_RESET_QEMU_VIRT_CTRL) += qemu-virt-ctrl.o
diff --git a/drivers/power/reset/qemu-virt-ctrl.c b/drivers/power/reset/qemu-virt-ctrl.c
new file mode 100644
index 000000000000..01409dfe2265
--- /dev/null
+++ b/drivers/power/reset/qemu-virt-ctrl.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * QEMU Virt Machine System Controller Driver
+ *
+ * Copyright (C) 2026 Kuan-Wei Chiu <visitorckw@gmail.com>
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+
+/* Registers */
+#define VIRT_CTRL_REG_FEATURES 0x00
+#define VIRT_CTRL_REG_CMD 0x04
+
+/* Commands */
+#define CMD_NOOP 0
+#define CMD_RESET 1
+#define CMD_HALT 2
+#define CMD_PANIC 3
+
+struct qemu_virt_ctrl {
+ void __iomem *base;
+ struct notifier_block reboot_nb;
+};
+
+static inline void virt_ctrl_write32(u32 val, void __iomem *addr)
+{
+ if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
+ iowrite32be(val, addr);
+ else
+ iowrite32(val, addr);
+}
+
+static int qemu_virt_ctrl_power_off(struct sys_off_data *data)
+{
+ struct qemu_virt_ctrl *ctrl = data->cb_data;
+
+ virt_ctrl_write32(CMD_HALT, ctrl->base + VIRT_CTRL_REG_CMD);
+
+ return NOTIFY_DONE;
+}
+
+static int qemu_virt_ctrl_restart(struct sys_off_data *data)
+{
+ struct qemu_virt_ctrl *ctrl = data->cb_data;
+
+ virt_ctrl_write32(CMD_RESET, ctrl->base + VIRT_CTRL_REG_CMD);
+
+ return NOTIFY_DONE;
+}
+
+static int qemu_virt_ctrl_reboot_notify(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ struct qemu_virt_ctrl *ctrl = container_of(nb, struct qemu_virt_ctrl, reboot_nb);
+
+ if (action == SYS_HALT)
+ virt_ctrl_write32(CMD_HALT, ctrl->base + VIRT_CTRL_REG_CMD);
+
+ return NOTIFY_DONE;
+}
+
+static int qemu_virt_ctrl_probe(struct platform_device *pdev)
+{
+ struct qemu_virt_ctrl *ctrl;
+ int ret;
+
+ ctrl = devm_kzalloc(&pdev->dev, sizeof(*ctrl), GFP_KERNEL);
+ if (!ctrl)
+ return -ENOMEM;
+
+ ctrl->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(ctrl->base))
+ return PTR_ERR(ctrl->base);
+
+ ret = devm_register_sys_off_handler(&pdev->dev,
+ SYS_OFF_MODE_RESTART,
+ SYS_OFF_PRIO_DEFAULT,
+ qemu_virt_ctrl_restart,
+ ctrl);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret,
+ "cannot register restart handler\n");
+
+ ret = devm_register_sys_off_handler(&pdev->dev,
+ SYS_OFF_MODE_POWER_OFF,
+ SYS_OFF_PRIO_DEFAULT,
+ qemu_virt_ctrl_power_off,
+ ctrl);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret,
+ "cannot register power-off handler\n");
+
+ ctrl->reboot_nb.notifier_call = qemu_virt_ctrl_reboot_notify;
+ ret = devm_register_reboot_notifier(&pdev->dev, &ctrl->reboot_nb);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "cannot register reboot notifier\n");
+
+ return 0;
+}
+
+static const struct platform_device_id qemu_virt_ctrl_id[] = {
+ { "qemu-virt-ctrl", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(platform, qemu_virt_ctrl_id);
+
+static struct platform_driver qemu_virt_ctrl_driver = {
+ .probe = qemu_virt_ctrl_probe,
+ .driver = {
+ .name = "qemu-virt-ctrl",
+ },
+ .id_table = qemu_virt_ctrl_id,
+};
+module_platform_driver(qemu_virt_ctrl_driver);
+
+MODULE_AUTHOR("Kuan-Wei Chiu <visitorckw@gmail.com>");
+MODULE_DESCRIPTION("QEMU Virt Machine System Controller Driver");
+MODULE_LICENSE("GPL");
--
2.53.0.1213.gd9a14994de-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v4 2/2] m68k: virt: Switch to qemu-virt-ctrl driver
2026-04-12 21:19 [PATCH v4 0/2] Add QEMU virt-ctrl driver and update m68k virt Kuan-Wei Chiu
2026-04-12 21:19 ` [PATCH v4 1/2] power: reset: Add QEMU virt-ctrl driver Kuan-Wei Chiu
@ 2026-04-12 21:19 ` Kuan-Wei Chiu
2026-04-13 10:19 ` [PATCH v4 0/2] Add QEMU virt-ctrl driver and update m68k virt Geert Uytterhoeven
2 siblings, 0 replies; 4+ messages in thread
From: Kuan-Wei Chiu @ 2026-04-12 21:19 UTC (permalink / raw)
To: geert, sre
Cc: jserv, eleanor15x, daniel, laurent, linux-kernel, linux-m68k,
linux-pm, Kuan-Wei Chiu
Register the "qemu-virt-ctrl" platform device during board
initialization to utilize the new generic power/reset driver.
Consequently, remove the legacy reset and power-off implementations
specific to the virt machine. The platform's mach_reset callback is
updated to call do_kernel_restart(), bridging the legacy m68k reboot
path to the generic kernel restart handler framework for this machine.
To prevent any regressions in reboot or power-off functionality when
the driver is not built-in, explicitly select POWER_RESET and
POWER_RESET_QEMU_VIRT_CTRL for the VIRT machine in Kconfig.machine.
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
arch/m68k/Kconfig.machine | 2 ++
arch/m68k/virt/config.c | 42 +--------------------------------------
arch/m68k/virt/platform.c | 20 ++++++++++++++++---
3 files changed, 20 insertions(+), 44 deletions(-)
diff --git a/arch/m68k/Kconfig.machine b/arch/m68k/Kconfig.machine
index de39f23b180e..624e6b27f394 100644
--- a/arch/m68k/Kconfig.machine
+++ b/arch/m68k/Kconfig.machine
@@ -133,6 +133,8 @@ config VIRT
select GOLDFISH_TIMER
select GOLDFISH_TTY
select M68040
+ select POWER_RESET
+ select POWER_RESET_QEMU_VIRT_CTRL
select RTC_CLASS
select RTC_DRV_GOLDFISH
select TTY
diff --git a/arch/m68k/virt/config.c b/arch/m68k/virt/config.c
index 632ba200ad42..b338e2a8da6a 100644
--- a/arch/m68k/virt/config.c
+++ b/arch/m68k/virt/config.c
@@ -13,18 +13,6 @@
struct virt_booter_data virt_bi_data;
-#define VIRT_CTRL_REG_FEATURES 0x00
-#define VIRT_CTRL_REG_CMD 0x04
-
-static struct resource ctrlres;
-
-enum {
- CMD_NOOP,
- CMD_RESET,
- CMD_HALT,
- CMD_PANIC,
-};
-
static void virt_get_model(char *str)
{
/* str is 80 characters long */
@@ -33,25 +21,9 @@ static void virt_get_model(char *str)
(u8)(virt_bi_data.qemu_version >> 16),
(u8)(virt_bi_data.qemu_version >> 8));
}
-
-static void virt_halt(void)
-{
- void __iomem *base = (void __iomem *)virt_bi_data.ctrl.mmio;
-
- iowrite32be(CMD_HALT, base + VIRT_CTRL_REG_CMD);
- local_irq_disable();
- while (1)
- ;
-}
-
static void virt_reset(void)
{
- void __iomem *base = (void __iomem *)virt_bi_data.ctrl.mmio;
-
- iowrite32be(CMD_RESET, base + VIRT_CTRL_REG_CMD);
- local_irq_disable();
- while (1)
- ;
+ do_kernel_restart(NULL);
}
/*
@@ -113,20 +85,8 @@ void __init config_virt(void)
virt_bi_data.tty.mmio);
setup_earlycon(earlycon);
- ctrlres = (struct resource)
- DEFINE_RES_MEM_NAMED(virt_bi_data.ctrl.mmio, 0x100,
- "virtctrl");
-
- if (request_resource(&iomem_resource, &ctrlres)) {
- pr_err("Cannot allocate virt controller resource\n");
- return;
- }
-
mach_init_IRQ = virt_init_IRQ;
mach_sched_init = virt_sched_init;
mach_get_model = virt_get_model;
mach_reset = virt_reset;
- mach_halt = virt_halt;
-
- register_platform_power_off(virt_halt);
}
diff --git a/arch/m68k/virt/platform.c b/arch/m68k/virt/platform.c
index 1560c4140ab9..764f556b4b32 100644
--- a/arch/m68k/virt/platform.c
+++ b/arch/m68k/virt/platform.c
@@ -30,7 +30,10 @@ static int __init virt_platform_init(void)
DEFINE_RES_MEM(virt_bi_data.rtc.mmio + 0x1000, 0x1000),
DEFINE_RES_IRQ(virt_bi_data.rtc.irq + 1),
};
- struct platform_device *pdev1, *pdev2;
+ const struct resource virt_ctrl_res[] = {
+ DEFINE_RES_MEM(virt_bi_data.ctrl.mmio, 0x100),
+ };
+ struct platform_device *pdev1, *pdev2, *pdev3;
struct platform_device *pdevs[VIRTIO_BUS_NB];
unsigned int i;
int ret = 0;
@@ -57,19 +60,30 @@ static int __init virt_platform_init(void)
goto err_unregister_tty;
}
+ pdev3 = platform_device_register_simple("qemu-virt-ctrl",
+ PLATFORM_DEVID_NONE,
+ virt_ctrl_res,
+ ARRAY_SIZE(virt_ctrl_res));
+ if (IS_ERR(pdev3)) {
+ ret = PTR_ERR(pdev3);
+ goto err_unregister_rtc;
+ }
+
for (i = 0; i < VIRTIO_BUS_NB; i++) {
pdevs[i] = virt_virtio_init(i);
if (IS_ERR(pdevs[i])) {
ret = PTR_ERR(pdevs[i]);
- goto err_unregister_rtc_virtio;
+ goto err_unregister_virtio;
}
}
return 0;
-err_unregister_rtc_virtio:
+err_unregister_virtio:
while (i > 0)
platform_device_unregister(pdevs[--i]);
+ platform_device_unregister(pdev3);
+err_unregister_rtc:
platform_device_unregister(pdev2);
err_unregister_tty:
platform_device_unregister(pdev1);
--
2.53.0.1213.gd9a14994de-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v4 0/2] Add QEMU virt-ctrl driver and update m68k virt
2026-04-12 21:19 [PATCH v4 0/2] Add QEMU virt-ctrl driver and update m68k virt Kuan-Wei Chiu
2026-04-12 21:19 ` [PATCH v4 1/2] power: reset: Add QEMU virt-ctrl driver Kuan-Wei Chiu
2026-04-12 21:19 ` [PATCH v4 2/2] m68k: virt: Switch to qemu-virt-ctrl driver Kuan-Wei Chiu
@ 2026-04-13 10:19 ` Geert Uytterhoeven
2 siblings, 0 replies; 4+ messages in thread
From: Geert Uytterhoeven @ 2026-04-13 10:19 UTC (permalink / raw)
To: Kuan-Wei Chiu
Cc: sre, jserv, eleanor15x, daniel, laurent, linux-kernel, linux-m68k,
linux-pm
Hi Kuan-Wei,
On Sun, 12 Apr 2026 at 23:20, Kuan-Wei Chiu <visitorckw@gmail.com> wrote:
> 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.
Thanks I replaced v3 with v4 in my queue in the m68k tree for v7.1,
and will postpone my PR by a few days to give it some coverage in
linux-next.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 4+ messages in thread