From: Shradha Gupta <[email protected]> Sent: Thursday, October 1, 2026 6:21 AM > > Kexec reboot fails on ARM64 Hyper-V guests because the VMBus > connection and SynIC CPU hotplug state are not torn down before the > secondary CPUs are stopped. The kexec kernel consequently starts with > the previous kernel's VMBus state still active. > > The previous version added an ARM64-specific syscore shutdown > implementation. This version follows Michael Kelley's review and moves > the cleanup into the existing architecture-independent VMBus syscore > operations. This removes the separate x86 handler dispatch and gives > x86 and ARM64 the same ordering: > > device_shutdown() > syscore_shutdown() > VMBus UNLOAD and SynIC CPU hotplug teardown > machine_shutdown() > > On x86, VMBus teardown now runs before hv_stimer_global_cleanup(). > This ordering is safe after commit be0cfab740e5 ("clocksource: hyper-v: > Remove support for stimer interrupts in message mode") removed the > VMBus dependency from synthetic timer handling. > > Patch 1 adds a read-only helper that reports whether a kexec reboot is > in progress. The helper is exported because HYPERV_VMBUS is tristate > and the common syscore callback must also link when VMBus is a module. > Patch 2 moves the cleanup into the common callback and removes the > obsolete architecture-specific setup/remove interface. > > For stable kernels that still support message-mode stimers, an > ARM64-specific backport will be needed to preserve the existing x86 > ordering. > > Changes in v3: > - Use the existing common VMBus syscore operations on all > architectures, as suggested by Michael. > - Remove the x86 handler pointer and the weak setup/remove interface. > - Add an exported read-only helper for modular VMBus builds. > - Correct the Fixes tag to the commit that enabled Hyper-V on ARM64. > > Changes in v2: > - Use syscore shutdown instead of an ARM64 machine_shutdown() hook, as > suggested by Catalin. > > Shradha Gupta (2): > kexec: Add helper to report an active kexec reboot > Drivers: hv: Run VMBus kexec cleanup from syscore shutdown > > arch/x86/kernel/cpu/mshyperv.c | 17 +---------------- > drivers/hv/hv_common.c | 10 ---------- > drivers/hv/vmbus_drv.c | 22 ++++++++++++++-------- > include/asm-generic/mshyperv.h | 2 -- > include/linux/kexec.h | 2 ++ > kernel/kexec_core.c | 7 +++++++ > 6 files changed, 24 insertions(+), 36 deletions(-) > > > base-commit: be0cfab740e58b70047ef6e7e3d578f00ed5d258 > -- > 2.43.0
Nice! Net impact is to remove 12 lines of code, instead of adding 40, which is great. And nothing under arch/arm64 is modified. One minor point: In hv_machine_shutdown(), we have two sequential tests of kexec_in_progress. Given that you are removing some code under the first test, I think it would be fair game to do a very minor refactoring of existing code and combine the two tests. It just looks a little funny to have the same test twice in a row. But regardless of whether you include that change, for the series, Reviewed-by: Michael Kelley <[email protected]>
