Re: [RFC PATCH 0/2] arm64/hyperv: Enable kexec reboot support

[Catalin Marinas]

On Fri, Aug 14, 2026 at 02:31:28AM -0700, Shradha Gupta wrote:
> Kexec reboot consistently fails on ARM64 Hyper-V guests (Azure VMs).
> During the kexec shutdown path, VMBus channels are never cleaned up,
> so in the fresh kexec kernel startup hv_acpi_init() blocks because
> the hypervisor still holds the old kernel's VMBus session open.
> 
> This is because ARM64 lacks the VMBus teardown that x86 performs during
> kexec via hv_machine_shutdown(). On x86, machine_ops.shutdown is
> overridden to send CHANNELMSG_UNLOAD and disable SynIC before CPUs
> go offline. ARM64 has no equivalent mechanism.

I'm really not keen on such hook, a bare pointer you set elsewhere. Not
sure it was discussed before but can you not use the syscore_shutdown()
mechanism? This hook got added in 2023, so the 2022 discussion you
referenced precedes it.

-- 
Catalin