[PATCH v6] arm64: sdei: abort running SDEI handlers during crash

[Mihai Carabas]

 > Interrupts are blocked in SDEI context, per the SDEI spec: "The client
 > interrupts cannot preempt the event handler." If we crashed in the SDEI
 > handler-running context (as with ACPI's AGDI) then we need to clean 
up the
 > SDEI state before proceeding to the crash kernel so that the crash kernel
 > can have working interrupts.
 >
 > Track the active SDEI handler per-cpu so that we can COMPLETE_AND_RESUME
 > the handler, discarding the interrupted context.

 > Fixes: f5df26961853 ("arm64: kernel: Add arch-specific SDEI entry 
code and CPU masking")
 > Signed-off-by: D Scott Phillips <scott at os.amperecomputing.com>

We have tested successfully this patch on Altra and AmpereOne.

Tested-by: Mihai Carabas <mihai.carabas at oracle.com>