[Qemu-ppc] spapr DRC and awaiting_allocation

[David Gibson]

Hi Bharata,

I'm trying to understand the awaiting_allocation flag in the DRC code,
and it's not making much sense to me.  It was introduced in aab9913
"spapr_drc: Prevent detach racing against attach for CPU DR", which
claims that a hot unplug racing with a not-completed hot plug of a CPU
can crash the guest.

The change made only appears to affect the case where this happens:
   host                         guest
   attach() CPU
   notify guest
   detach() CPU
                                RTAS set_allocation_state USABLE

But in that case, I'd expect the set_allocation_state to simply fail
(becuase the DRC is now awaiting_release) and for the guest to cope
with that failure.

Can you remember the mechanism by which the guest was crashed?

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

signature.asc
Description: PGP signature