Re: [PATCH v3 0/2] hyperv: Run VMBus kexec cleanup from syscore shutdown

[Bradley Morgan]

On 1 October 2026 14:21:25 BST, Shradha Gupta
<shradhagupta@xxxxxxxxxxxxxxxxxxx> wrote:
>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
>

Wow! Great!!!

Whole series:

Reviewed-by: Bradley Morgan <brads@xxxxxxxxxxxxxx>

--- Thanks!
"I'm not a very positive person" - Linus torvalds