[Qemu-devel] [PATCH for-2.6] spapr_drc: fix aborts during DRC-count based hotplug

[Michael Roth <mdroth@linux.vnet.ibm.com>]

CPU/memory resources can be signalled en-masse via
spapr_hotplug_req_add_by_count(), and when doing so, actually change
the meaning of the 'drc' parameter passed to
spapr_hotplug_req_event() to be a count rather than an index.

f40eb92 added a hook in spapr_hotplug_req_event() to record when a
device had been 'signalled' to the guest, but that code assumes that
drc is always an index. In cases where it's a count, such as memory
hotplug, the DRC lookup will fail, leading to an assert.

Fix this by only explicitly setting the signalled state for cases where
we are doing PCI hotplug.

For other resources types, since we cannot selectively track whether a
resource has been signalled in cases where we signal attach as a count,
set the 'signalled' state to true immediately upon making the
resource available via drck->attach().

Reported-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: david@gibson.dropbear.id.au
Cc: qemu-ppc@nongnu.org
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
Really sorry for the way last-minute fix, but without this memory hotplug
is totally broken :( Hoping to get this in for Wednesday's RC4, which
I think will be the final before release.
---
 hw/ppc/spapr_drc.c    | 12 +++++++++++-
 hw/ppc/spapr_events.c |  7 +++----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
index 3173940..1f5f1d7 100644
--- a/hw/ppc/spapr_drc.c
+++ b/hw/ppc/spapr_drc.c
@@ -364,7 +364,17 @@ static void attach(sPAPRDRConnector *drc, DeviceState *d, void *fdt,
     drc->fdt = fdt;
     drc->fdt_start_offset = fdt_start_offset;
     drc->configured = coldplug;
-    drc->signalled = coldplug;
+    /* 'logical' DR resources such as memory/cpus are in some cases treated
+     * as a pool of resources from which the guest is free to choose from
+     * based on only a count. for resources that can be assigned in this
+     * fashion, we must assume the resource is signalled immediately
+     * since a single hotplug request might make an arbitrary number of
+     * such attached resources available to the guest, as opposed to
+     * 'physical' DR resources such as PCI where each device/resource is
+     * signalled individually.
+     */
+    drc->signalled = (drc->type != SPAPR_DR_CONNECTOR_TYPE_PCI)
+                     ? true : coldplug;
 
     object_property_add_link(OBJECT(drc), "device",
                              object_get_typename(OBJECT(drc->dev)),
diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
index 269ab7e..049fb1b 100644
--- a/hw/ppc/spapr_events.c
+++ b/hw/ppc/spapr_events.c
@@ -442,6 +442,9 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t hp_action,
     switch (drc_type) {
     case SPAPR_DR_CONNECTOR_TYPE_PCI:
         hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_PCI;
+        if (hp->hotplug_action == RTAS_LOG_V6_HP_ACTION_ADD) {
+            spapr_hotplug_set_signalled(drc);
+        }
         break;
     case SPAPR_DR_CONNECTOR_TYPE_LMB:
         hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_MEMORY;
@@ -462,10 +465,6 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t hp_action,
 
     rtas_event_log_queue(RTAS_LOG_TYPE_HOTPLUG, new_hp, true);
 
-    if (hp->hotplug_action == RTAS_LOG_V6_HP_ACTION_ADD) {
-        spapr_hotplug_set_signalled(drc);
-    }
-
     qemu_irq_pulse(xics_get_qirq(spapr->icp, spapr->check_exception_irq));
 }
 
-- 
1.9.1