[Skiboot] [RFC/WIP/PATCH v2] Fast reboot for P8

[Stewart Smith]

Michael Neuling <mikey at neuling.org> writes:
> On Wed, 2016-07-27 at 15:31 +1000, Michael Neuling wrote:
>> > 
>> > This is an experimental patch that implements "Fast reboot" on P8
>> > machines.
>> >  
>> > The basic idea is that when the OS calls OPAL reboot, we gather all
>> > the threads in the system using a combination of patching the reset
>> > vector and soft-resetting them, then cleanup a few bits of hardware
>> > (we do re-probe PCIe for example), and reload & restart the bootloader.
>> Awesome!!!
>> 
>> FWIW This is an additional patch to get it to work with 1 CPU on mambo.
>  It
>> works nicely if you pass in a PNOR image via bogus disk. It'll reload the
>> kernel & petitboot on each reboot.
>
> Here's a slightly better version that handles multi-core/thread.
>
> It uses the mambo callthru to run a tcl command to send the CPUs to
> 0x100.
>
> mambo confuses skiboot a bit when the topology doesn't match real
> hardware (eg. when mambo configures a power8 with less than 8
> threads).  So we need to fix that up at some point.

So, with your mangled patch (Evolution really is trying to be "enterprise" at
sending mail these days), I managed to bring in the changes anyway as
part of merging fast-reset.

It may not be perfect though... I still hit an issue with
random-old-mambo-tree-compiled-on-stewart's-laptop (that's always the
*best* version of anything).

> mambo also seems to have some issues with not running any instructions
> on the threads when they are sent to 0x100 for many seconds. This
> means the reboot takes much longer than it needs to with many threads.
> We may need to reset the thread priorities to fix this.

Hrm... I wonder if that's it....



-- 
Stewart Smith
OPAL Architect, IBM.