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Re: [Qemu-devel] [PATCH v3] qdev/core: fix qbus_is_full()
From: |
Igor Mammedov |
Subject: |
Re: [Qemu-devel] [PATCH v3] qdev/core: fix qbus_is_full() |
Date: |
Tue, 18 Dec 2018 15:18:48 +0100 |
On Mon, 17 Dec 2018 10:57:30 -0500
Tony Krowiak <address@hidden> wrote:
> 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: Tony Krowiak <address@hidden>
> Reviewed-by: Pierre Morel<address@hidden>
> Reviewed-by: Halil Pasic <address@hidden>
Reviewed-by: Igor Mammedov <address@hidden>
> ---
> hw/core/qdev.c | 3 +++
> include/hw/qdev-core.h | 1 +
> qdev-monitor.c | 2 +-
> 3 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 6b3cc55b27c2..956923f33520 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -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));
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index a24d0dd566e3..521f0a947ead 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -206,6 +206,7 @@ struct BusState {
> HotplugHandler *hotplug_handler;
> int max_index;
> bool realized;
> + int num_children;
> QTAILQ_HEAD(ChildrenHead, BusChild) children;
> QLIST_ENTRY(BusState) sibling;
> };
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index 07147c63bf8b..45a8ba49644c 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -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;
> }
>
> /*