[PATCH v2] arm64: hyperv: run VMBus kexec handler via syscore shutdown
From: Shradha Gupta <hidden>
Date: 2026-09-07 09:26:43
Also in:
linux-arm-kernel, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
On ARM64, machine_shutdown() does not provide a platform hook between
device_shutdown() and smp_shutdown_nonboot_cpus(), unlike x86's
machine_ops.shutdown. This prevents the Hyper-V VMBus kexec handler
from running at the correct point during kexec shutdown, causing
kexec reboot to fail on ARM64 Hyper-V guests.
Use syscore_ops.shutdown instead: syscore_shutdown() runs in the same
window (after device_shutdown(), before CPUs are taken offline) where
VMBus UNLOAD and cpuhp_remove_state() must execute.
Provide ARM64-specific overrides of hv_setup_kexec_handler() and
hv_remove_kexec_handler() that register/unregister a syscore_ops
shutdown callback, replacing the __weak no-op stubs in hv_common.c.
On x86, the existing machine_ops.shutdown mechanism is unchanged.
Fixes: 9d7cf2c96758 ("Drivers: hv: Add arch independent default functions for some Hyper-V handlers")
Link: https://lore.kernel.org/all/20260814093133.3191250-1-shradhagupta@linux.microsoft.com/ (local)
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Shradha Gupta <redacted>
Reviewed-by: Naman Jain <redacted>
---
Changes in V2
* Use syscore_ops.shutdown instead of a bare function pointer hook in
machine_shutdown(), per Catalin's suggestion.
---
arch/arm64/hyperv/mshyperv.c | 40 ++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
index 4fdc26ade1d7..e608e546a395 100644
--- a/arch/arm64/hyperv/mshyperv.c
+++ b/arch/arm64/hyperv/mshyperv.c@@ -15,10 +15,50 @@ #include <linux/errno.h> #include <linux/version.h> #include <linux/cpuhotplug.h> +#include <linux/kexec.h> +#include <linux/syscore_ops.h> #include <asm/mshyperv.h> static bool hyperv_initialized; +/* + * Kexec handler registered by VMBus. + * + * On ARM64, machine_shutdown() does not provide a platform hook between + * device_shutdown() and smp_shutdown_nonboot_cpus(), unlike the + * machine_ops.shutdown mechanism used on x86. Use a syscore_ops shutdown + * callback instead: syscore_shutdown() runs after device_shutdown() and + * before CPUs are taken offline, which is the same window VMBus needs to + * run its UNLOAD message and cpuhp_remove_state() during kexec. + */ +static void (*hv_kexec_handler_fn)(void); + +static void hv_kexec_syscore_shutdown(void *data) +{ + if (kexec_in_progress && hv_kexec_handler_fn) + hv_kexec_handler_fn(); +} + +static const struct syscore_ops hv_kexec_syscore_ops = { + .shutdown = hv_kexec_syscore_shutdown, +}; + +static struct syscore hv_kexec_syscore = { + .ops = &hv_kexec_syscore_ops, +}; + +void hv_setup_kexec_handler(void (*handler)(void)) +{ + hv_kexec_handler_fn = handler; + register_syscore(&hv_kexec_syscore); +} + +void hv_remove_kexec_handler(void) +{ + unregister_syscore(&hv_kexec_syscore); + hv_kexec_handler_fn = NULL; +} + int hv_get_hypervisor_version(union hv_hypervisor_version_info *info) { hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION,
--
2.43.0