On Mon, Feb 03, 2020 at 11:36:22PM +0100, Greg Kurz wrote: > Hot unplugging a device is an asynchronous operation. If the guest is > migrated after the event was sent but before it could release the > device with RTAS, the destination QEMU doesn't know about the pending > unplug operation and doesn't actually remove the device when the guest > finally releases it. The device > > Migrate SpaprDrc::unplug_requested to fix the inconsistency. This is > done with a subsection that is only sent if an unplug request is > pending. This allows to preserve migration with older guests in the > case of a pending hotplug request. This will cause migration to fail > if the destination can't handle the subsection, but this is better > than ending with an inconsistency. > > Signed-off-by: Greg Kurz <gr...@kaod.org> > --- > hw/ppc/spapr_drc.c | 27 +++++++++++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-) > > diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c > index d512ac6e1e7f..6f5cab70fc6b 100644 > --- a/hw/ppc/spapr_drc.c > +++ b/hw/ppc/spapr_drc.c > @@ -455,6 +455,22 @@ void spapr_drc_reset(SpaprDrc *drc) > } > } > > +static bool spapr_drc_unplug_requested_needed(void *opaque) > +{ > + return spapr_drc_unplug_requested(opaque); > +} > + > +static const VMStateDescription vmstate_spapr_drc_unplug_requested = { > + .name = "spapr_drc/unplug_requested", > + .version_id = 1, > + .minimum_version_id = 1, > + .needed = spapr_drc_unplug_requested_needed, > + .fields = (VMStateField []) { > + VMSTATE_BOOL(unplug_requested, SpaprDrc), > + VMSTATE_END_OF_LIST() > + } > +}; > + > static bool spapr_drc_needed(void *opaque) > { > SpaprDrc *drc = (SpaprDrc *)opaque; > @@ -467,8 +483,11 @@ static bool spapr_drc_needed(void *opaque) > /* > * We need to migrate the state if it's not equal to the expected > * long-term state, which is the same as the coldplugged initial > - * state */ > - return !spapr_drc_device_ready(drc); > + * state, or if an unplug request is pending. > + */ > + return > + spapr_drc_unplug_requested_needed(drc) || > + !spapr_drc_device_ready(drc);
Hrm. You start the series by splitting spapr_drc_device_ready() from spapr_drc_needed(). But at this point, I'm pretty sure you've now got all the callers of spapr_drc_device_ready() doing equivalent logic about them, so they might as well be one function again. That seems pretty roundabout. I don't think the rationale for not using the drc_ready function from the CAS path really makes sense. It's not just an accident that those use the same logic - in both cases what we're testing is "Is the DRC in a state other than that of a default cold-plugged device?". Changing the name might be sensible, but I still think we want a common function for the two cases. > } > > static const VMStateDescription vmstate_spapr_drc = { > @@ -479,6 +498,10 @@ static const VMStateDescription vmstate_spapr_drc = { > .fields = (VMStateField []) { > VMSTATE_UINT32(state, SpaprDrc), > VMSTATE_END_OF_LIST() > + }, > + .subsections = (const VMStateDescription * []) { > + &vmstate_spapr_drc_unplug_requested, > + NULL > } > }; > > -- 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