Drivers: hv: Run VMBus kexec cleanup from syscore shutdown

ARM64 Hyper-V guests do not run the VMBus kexec cleanup before
secondary CPUs are stopped. Consequently, the old VMBus connection
and SynIC state remain active when the kexec kernel starts.

Run the VMBus kexec handler from the existing VMBus syscore shutdown
callback. syscore_shutdown() runs after device shutdown and before
machine shutdown, while all CPUs needed by the SynIC CPU hotplug
teardown are still available. Guard the callback with
kexec_is_in_progress() so normal restart, halt, and poweroff paths are
unchanged.

Use the same path on x86 and remove the architecture-specific handler
pointer and the weak setup/remove interfaces. VMBus teardown now
precedes hv_stimer_global_cleanup() on x86.

The new x86 ordering relies on commit be0cfab740e5 ("clocksource:
hyper-v: Remove support for stimer interrupts in message mode"), which
removed the synthetic timer's dependency on VMBus message delivery.
Older kernels that retain message-mode stimer interrupts must preserve
the existing x86 ordering and therefore require an ARM64-specific
backport.

Document the VMBus cleanup path and its position in shutdown ordering.

Fixes: 9bbb888824e3 ("arm64: hyperv: Initialize hypervisor on boot")
Link: https://lore.kernel.org/all/20260814093133.3191250-1-shradhagupta@linux.microsoft.com/
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Suggested-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Reviewed-by: Naman Jain <namjain@linux.microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

0 files changed, 0 insertions, 0 deletions