On Wed, Nov 30, 2016 at 05:05:34PM -0600, Michael Roth wrote: > Currently we set the initial isolation/allocation state for DRCs > associated with coldplugged LMBs to ISOLATED/UNUSABLE, > respectively, under the assumption that the guest will move this > state to UNISOLATED/USABLE. > > In fact, this is only the case for LMBs added via hotplug. For > coldplugged LMBs, the guest actually assumes the initial state to > be UNISOLATED/USABLE. > > In practice, this only becomes an issue when we attempt to unplug > one of these LMBs, where the guest kernel will issue an > rtas-get-sensor-state call to check that the corresponding DRC is > in an USABLE state before it will release the LMB back to > QEMU. If the returned state is otherwise, the guest will assume no > further action is needed, which bypasses the QEMU-side cleanup that > occurs during the USABLE->UNUSABLE transition. This results in > LMBs and their corresponding pc-dimm devices to stick around > indefinitely. > > This patch fixes the issue by manually setting DRCs associated with > cold-plugged LMBs to UNISOLATED/ALLOCATED, but leaving the hotplug > state untouched. As it turns out, this is analogous to the handling > for cold-plugged CPUs in spapr_core_plug(). > > Cc: qemu-...@nongnu.org > Cc: David Gibson <da...@gibson.dropbear.id.au> > Cc: Bharata B Rao <bhar...@linux.vnet.ibm.com> > Cc: Greg Kurz <gk...@linux.vnet.ibm.com> > Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com> > --- > This patch is a revision to the previously posted series: > > [PATCH for-2.8 0/3] spapr: fix breakage of memory unplug after migration > > That patchset introduced DRC migration as a means to address DRC state > synchronization between source/target to allow memory unplug after > migration. It turns out that unplug was also not working for LMBs > that were defined on the source via '-device pc-dimm'. The real issue > was that the default coldplug state on *both* the source and target was > wrong, and by fixing that default state, we no longer need DRC migration > for the scenario mentioned in the previous patchset since, incidentally, > coldplug state on the target now matches post-hotplug DRC state on the > source. > > This patch is very late for 2.8, but I'm hoping it can still make it > in for rc3/2.8. > > I've tested forward/backward migration for all possible combinations > (other than known case unsupported case 2.8->2.7) of > v2.6/v2.7/v2.8, pseries-2.6/pseries-2.7/pseries-2.8, and > modern-hotplug-events=true/false, with various combinations of > CPU / LMB hotplug/unplug before/after migration.
I've merged this to ppc-for-2.8. I'll begin my test cycle and see if
we can send a pull request in time.
> ---
> hw/ppc/spapr.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index c3269c7..208ef7b 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2290,6 +2290,11 @@ static void spapr_add_lmbs(DeviceState *dev, uint64_t
> addr_start, uint64_t size,
> drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, errp);
> addr += SPAPR_MEMORY_BLOCK_SIZE;
> + if (!dev->hotplugged) {
> + /* guests expect coldplugged LMBs to be pre-allocated */
> + drck->set_allocation_state(drc,
> SPAPR_DR_ALLOCATION_STATE_USABLE);
> + drck->set_isolation_state(drc,
> SPAPR_DR_ISOLATION_STATE_UNISOLATED);
> + }
> }
> /* send hotplug notification to the
> * guest only in case of hotplugged memory
--
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
