kexec-xen: Allow xen_kexec_exec() to return in case of Live Update

Currently, my_exec() does not expect the Xen KEXEC_CMD_kexec hypercall
to return on success, because it assumes that the hypercall always
triggers an immediate reboot. However, for Live Update, the hypercall
merely schedules the kexec operation and returns; the actual reboot
happens asynchronously. [1]

Therefore, rework the Xen code path of my_exec() such that it does not
treat a successfully processed Live Update request as an error. Also,
rephrase the comment above the function to remove ambiguity.

[1] https://lists.xen.org/archives/html/xen-devel/2021-05/msg00286.html

Signed-off-by: Raphael Ning <raphning@amazon.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
3 files changed