From 930ef3b5c212bf8056bd265cc43ed9fff2e31b08 Mon Sep 17 00:00:00 2001 From: Greg Kurz Date: Fri, 18 Dec 2020 11:33:56 +0100 Subject: [PATCH] spapr: Fix reset of transient DR connectors Documentation of object_property_iter_init() clearly stipulates that "it is forbidden to modify the property list while iterating". But this is exactly what we do when resetting transient DR connectors during CAS. The call to spapr_drc_reset() can finalize the hot-unplug sequence of a PHB or a PCI bridge, both of which will then in turn destroy their PCI DRCs. This could potentially invalidate the iterator. It is pure luck that this haven't caused any issues so far. Change spapr_drc_reset() to return true if it caused a device to be removed. Restart from scratch in this case. This can potentially increase the overall DRC reset time, especially with a high maxmem which generates a lot of LMB DRCs. But this kind of setup is rare, and so is the use case of rebooting a guest while doing hot-unplug. Signed-off-by: Greg Kurz Message-Id: <20201218103400.689660-3-groug@kaod.org> Reviewed-by: Daniel Henrique Barboza Tested-by: Daniel Henrique Barboza Signed-off-by: David Gibson --- hw/ppc/spapr_drc.c | 6 +++++- hw/ppc/spapr_hcall.c | 8 +++++++- include/hw/ppc/spapr_drc.h | 3 ++- 3 files changed, 14 insertions(+), 3 deletions(-) diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c index 8d62f55066..5b5e2ac58a 100644 --- a/hw/ppc/spapr_drc.c +++ b/hw/ppc/spapr_drc.c @@ -417,9 +417,10 @@ void spapr_drc_detach(SpaprDrc *drc) spapr_drc_release(drc); } -void spapr_drc_reset(SpaprDrc *drc) +bool spapr_drc_reset(SpaprDrc *drc) { SpaprDrcClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc); + bool unplug_completed = false; trace_spapr_drc_reset(spapr_drc_index(drc)); @@ -428,6 +429,7 @@ void spapr_drc_reset(SpaprDrc *drc) */ if (drc->unplug_requested) { spapr_drc_release(drc); + unplug_completed = true; } if (drc->dev) { @@ -444,6 +446,8 @@ void spapr_drc_reset(SpaprDrc *drc) drc->ccs_offset = -1; drc->ccs_depth = -1; } + + return unplug_completed; } static bool spapr_drc_unplug_requested_needed(void *opaque) diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c index 4e9d50c254..aa22830ac4 100644 --- a/hw/ppc/spapr_hcall.c +++ b/hw/ppc/spapr_hcall.c @@ -1639,6 +1639,7 @@ static void spapr_handle_transient_dev_before_cas(SpaprMachineState *spapr) ObjectPropertyIterator iter; drc_container = container_get(object_get_root(), "/dr-connector"); +restart: object_property_iter_init(&iter, drc_container); while ((prop = object_property_iter_next(&iter))) { SpaprDrc *drc; @@ -1652,8 +1653,13 @@ static void spapr_handle_transient_dev_before_cas(SpaprMachineState *spapr) /* * This will complete any pending plug/unplug requests. + * In case of a unplugged PHB or PCI bridge, this will + * cause some DRCs to be destroyed and thus potentially + * invalidate the iterator. */ - spapr_drc_reset(drc); + if (spapr_drc_reset(drc)) { + goto restart; + } } spapr_clear_pending_hotplug_events(spapr); diff --git a/include/hw/ppc/spapr_drc.h b/include/hw/ppc/spapr_drc.h index cff5e707d0..5d80019f82 100644 --- a/include/hw/ppc/spapr_drc.h +++ b/include/hw/ppc/spapr_drc.h @@ -224,7 +224,8 @@ static inline bool spapr_drc_hotplugged(DeviceState *dev) return dev->hotplugged && !runstate_check(RUN_STATE_INMIGRATE); } -void spapr_drc_reset(SpaprDrc *drc); +/* Returns true if an unplug request completed */ +bool spapr_drc_reset(SpaprDrc *drc); uint32_t spapr_drc_index(SpaprDrc *drc); SpaprDrcType spapr_drc_type(SpaprDrc *drc);