Commit 12b2e9f3 authored by Tony Krowiak's avatar Tony Krowiak Committed by Eduardo Habkost
Browse files

qdev/core: fix qbus_is_full() 



The qbus_is_full(BusState *bus) function (qdev_monitor.c) compares the max_index
value of the BusState structure with the max_dev value of the BusClass structure
to determine whether the maximum number of children has been reached for the
bus. The problem is, the max_index field of the BusState structure does not
necessarily reflect the number of devices that have been plugged into
the bus.

Whenever a child device is plugged into the bus, the bus's max_index value is
assigned to the child device and then incremented. If the child is subsequently
unplugged, the value of the max_index does not change and no longer reflects the
number of children.

When the bus's max_index value reaches the maximum number of devices
allowed for the bus (i.e., the max_dev field in the BusClass structure),
attempts to plug another device will be rejected claiming that the bus is
full -- even if the bus is actually empty.

To resolve the problem, a new 'num_children' field is being added to the
BusState structure to keep track of the number of children plugged into the
bus. It will be incremented when a child is plugged, and decremented when a
child is unplugged.

Signed-off-by: default avatarTony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: default avatarPierre <Morel&lt;pmorel@linux.ibm.com>
Reviewed-by: default avatarHalil Pasic <pasic@linux.ibm.com>
Message-Id: <1545062250-7573-1-git-send-email-akrowiak@linux.ibm.com>
Reviewed-by: default avatarIgor Mammedov <imammedo@redhat.com>
Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
parent 9b748c5e

hw/core/qdev.c

+3 −0
Original line number Diff line number Diff line
@@ -59,6 +59,8 @@ static void bus_remove_child(BusState *bus, DeviceState *child) 
            snprintf(name, sizeof(name), "child[%d]", kid->index);

            QTAILQ_REMOVE(&bus->children, kid, sibling);



            bus->num_children--;



            /* This gives back ownership of kid->child back to us.  */

            object_property_del(OBJECT(bus), name, NULL);

            object_unref(OBJECT(kid->child));
@@ -73,6 +75,7 @@ static void bus_add_child(BusState *bus, DeviceState *child) 
    char name[32];

    BusChild *kid = g_malloc0(sizeof(*kid));



    bus->num_children++;

    kid->index = bus->max_index++;

    kid->child = child;

    object_ref(OBJECT(kid->child));

include/hw/qdev-core.h

+1 −0
Original line number Diff line number Diff line
@@ -206,6 +206,7 @@ struct BusState { 
    HotplugHandler *hotplug_handler;

    int max_index;

    bool realized;

    int num_children;

    QTAILQ_HEAD(, BusChild) children;

    QLIST_ENTRY(BusState) sibling;

};

qdev-monitor.c

+1 −1
Original line number Diff line number Diff line
@@ -414,7 +414,7 @@ static DeviceState *qbus_find_dev(BusState *bus, char *elem) 
static inline bool qbus_is_full(BusState *bus)

{

    BusClass *bus_class = BUS_GET_CLASS(bus);

    return bus_class->max_dev && bus->max_index >= bus_class->max_dev;

    return bus_class->max_dev && bus->num_children >= bus_class->max_dev;

}



/*