On Fri, Nov 18, 2016 at 10:08:59AM -0600, Michael Roth wrote:
> Quoting Michael Roth (2016-11-17 19:40:27)
> > With the additional of the OV5_HP_EVT option vector, we now have
> > certain functionality (namely, memory unplug) that checks at run-time
> > for whether or not the guest negotiated the option via CAS. Because
> > we don't currently migrate these negotiated values, we are unable
> > to unplug memory from a guest after it's been migrated until after
> > the guest is rebooted and CAS-negotiation is repeated.
> >
> > This patch fixes this by adding CAS-negotiated options to the
> > migration stream. We do this using a subsection, since the
> > negotiated value of OV5_HP_EVT is the only option currently needed
> > to maintain proper functionality for a running guest.
> >
> > Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
> > ---
> > hw/ppc/spapr.c | 68
> > +++++++++++++++++++++++++++++++++++++++++++++
> > hw/ppc/spapr_ovec.c | 12 ++++++++
> > include/hw/ppc/spapr_ovec.h | 4 +++
> > 3 files changed, 84 insertions(+)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 0cbab24..9e08aed 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1267,6 +1267,70 @@ static bool version_before_3(void *opaque, int
> > version_id)
> > return version_id < 3;
> > }
> >
> > +static bool spapr_ov5_cas_needed(void *opaque)
> > +{
> > + sPAPRMachineState *spapr = opaque;
> > + sPAPROptionVector *ov5_mask = spapr_ovec_new();
> > + sPAPROptionVector *ov5_legacy = spapr_ovec_new();
> > + sPAPROptionVector *ov5_removed = spapr_ovec_new();
> > + bool cas_needed;
> > +
> > + /* Prior to the introduction of sPAPROptionVector, we had two option
> > + * vectors we dealt with: OV5_FORM1_AFFINITY, and OV5_DRCONF_MEMORY.
> > + * Both of these options encode machine topology into the device-tree
> > + * in such a way that the now-booted OS should still be able to
> > interact
> > + * appropriately with QEMU regardless of what options were actually
> > + * negotiatied on the source side.
> > + *
> > + * As such, we can avoid migrating the CAS-negotiated options if these
> > + * are the only options available on the current machine/platform.
> > + * Since these are the only options available for pseries-2.7 and
> > + * earlier, this allows us to maintain old->new/new->old migration
> > + * compatibility.
> > + *
> > + * For QEMU 2.8+, there are additional CAS-negotiatable options
> > available
> > + * via default pseries-2.8 machines and explicit command-line
> > parameters.
> > + * Some of these options, like OV5_HP_EVT, *do* require QEMU to be
> > aware
> > + * of the actual CAS-negotiated values to continue working properly.
> > For
> > + * example, availability of memory unplug depends on knowing whether
> > + * OV5_HP_EVT was negotiated via CAS.
> > + *
> > + * Thus, for any cases where the set of available CAS-negotiatable
> > + * options extends beyond OV5_FORM1_AFFINITY and OV5_DRCONF_MEMORY, we
> > + * include the CAS-negotiated options in the migration stream.
> > + */
> > + spapr_ovec_set(ov5_mask, OV5_FORM1_AFFINITY);
> > + spapr_ovec_set(ov5_mask, OV5_DRCONF_MEMORY);
> > +
> > + /* spapr_ovec_diff returns true if bits were removed. we avoid using
> > + * the mask itself since in the future it's possible "legacy" bits may
> > be
> > + * removed via machine options, which could generate a false positive
> > + * that breaks migration.
> > + */
> > + spapr_ovec_intersect(ov5_legacy, spapr->ov5, ov5_mask);
> > + cas_needed = spapr_ovec_diff(ov5_removed, spapr->ov5, ov5_legacy);
> > +
> > + spapr_ovec_cleanup(ov5_mask);
> > + spapr_ovec_cleanup(ov5_legacy);
> > + spapr_ovec_cleanup(ov5_removed);
> > +
> > + error_report("MIGRATION NEEDED: %d", cas_needed);
>
> Argh, sorry, I just noticed this stray debug comment that slipped in.
> Would you prefer a v2, or just removing it in-tree?
I've fixed it in tree. Thanks for pointing it out.
--
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
