Hi folks, this email is to ask feedback / trigger a discussion about the concept of custom crash shutdown handler, that is "missing" in arm64 while it's present in many architectures [mips, powerpc, x86, sh (!)]. Currently, when we kexec in arm64, the function machine_crash_shutdown() is called as a handler to disable CPUs and (potentially) do extra quiesce work. In the aforementioned architectures, there's a way to override this function, if for example an hypervisor wish to have its guests running their own custom shutdown machinery. For powerpc/mips, the approach is a generic shutdown function that might call other handler-registered functions, whereas x86/sh relies in the "machine_ops" structure, having the crash shutdown as a callback in such struct. The usage for that is very broad, but heavy users are hypervisors like Hyper-V / KVM (CCed Michael and Vitaly here for this reason). The discussion about the need for that in arm64 is from another thread [0], so before start implementing/playing with that, I'd like to ask ARM64 community if there is any feedback and in case it's positive, what is the best implementation strategy (struct callback vs. handler call), etc. I've CCed ARM64/ARM32 maintainers plus extra people I found as really involved with ARM architecture - sorry if I added people I shouldn't or if I forgot somebody (though the ARM mailing-list is CC). Cheers, Guilherme [0] https://lore.kernel.org/lkml/2787b476-6366-1c83-db80-0393da417497@xxxxxxxxxx/ See the proposed option (b)
