Logical resources start with allocation-state:UNUSABLE /
isolation-state:ISOLATED. During hotplug, guests will transition
them to allocate-state:USABLE, and then to isolate-state:UNISOLATED.
The former transition does not seem to have any failure path for
cases where a DRC does not have any resources associated with it to
allocate for guest, but instead relies on the subsequent
isolation-state:UNISOLATED transition to indicate failure in this
situation.
Currently DRC code does not implement this logic, but instead
tries to indicate failure by refusing the allocation-state:USABLE
transition. Unfortunately, since that's not a documented failure
path, guests continue undeterred, causing undefined behavior in
QEMU and guest code.
Fix this by handling things as PAPR defines (13.7 and 13.7.3.1).
Cc: qemu-...@nongnu.org
Cc: David Gibson <da...@gibson.dropbear.id.au>
Cc: Bharata B Rao <bhar...@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
---
hw/ppc/spapr_drc.c | 12 ++++++++++++
include/hw/ppc/spapr_drc.h | 2 ++
2 files changed, 14 insertions(+)
diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
index 9ce844a..c1f664f 100644
--- a/hw/ppc/spapr_drc.c
+++ b/hw/ppc/spapr_drc.c
@@ -66,6 +66,18 @@ static int set_isolation_state(sPAPRDRConnector *drc,
DPRINTFN("drc: %x, set_isolation_state: %x", get_index(drc), state);
+ if (state == SPAPR_DR_ISOLATION_STATE_UNISOLATED) {
+ /* cannot unisolate a non-existant resource. this generally
+ * happens for logical resources where transitions from
+ * allocation-state:UNUSABLE to allocation-state:USABLE are
+ * unguarded, but instead rely on a subsequent
+ * isolation-state:UNISOLATED transition to indicate failure
+ */
+ if (!drc->dev) {
+ return -1;
+ }
+ }
+
drc->isolation_state = state;
if (drc->isolation_state == SPAPR_DR_ISOLATION_STATE_ISOLATED) {
diff --git a/include/hw/ppc/spapr_drc.h b/include/hw/ppc/spapr_drc.h
index 28ffeae..3fbe9ea 100644
--- a/include/hw/ppc/spapr_drc.h
+++ b/include/hw/ppc/spapr_drc.h
@@ -109,6 +109,7 @@ typedef enum {
* unusable: device not currently available to OS
* exchange: (currently unused)
* recover: (currently unused)
+ * no_sensor: for logical DR only, returned when no resource available
*/
typedef enum {
SPAPR_DR_ENTITY_SENSE_EMPTY = 0,
@@ -116,6 +117,7 @@ typedef enum {
SPAPR_DR_ENTITY_SENSE_UNUSABLE = 2,
SPAPR_DR_ENTITY_SENSE_EXCHANGE = 3,
SPAPR_DR_ENTITY_SENSE_RECOVER = 4,
+ SPAPR_DR_ENTITY_SENSE_NO_SENSOR = -3,
} sPAPRDREntitySense;
typedef enum {
--
1.9.1
