[OpenPower-Firmware] SRESET and idle CPU

[Stewart Smith]

On Fri, Jul 24, 2020, at 3:14 AM, Artem Senichev wrote:
> Hi all,
> 
> Our customers want to be able to initiate kdump on a POWER9 host system 
> from BMC console.
> I tried to implement this functionality with an SRESET signal sent 
> through the pdbg utility, but it turned out that when the CPU is in an 
> idle state (sleep), the signal could not be delivered.
> 
> I can disable the idle state on a host:
> 
> for i in /sys/devices/system/cpu/cpu0/cpuidle/state*/disable; do
>   echo 1 > $i
> done
> 
> and then send SRESET from BMC:
> 
> pdbg -p0 -c0 -t0 stop
> pdbg -p0 -c0 -t0 sreset
> 
> This solution works fine, but I need to do it without interfering with 
> the host system.
> Is it possible?

IIRC you have to do a special wakeup in order to sreset idle cpus. Skiboot should do this when it's doing sreset from the host. I also *think* there might be a SBE chipop to do this on P9? If not, there possibly should be, as otherwise you're relying on secure boot not being around.