| Message ID | 1544469254-11629-1-git-send-email-akrowiak@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | qdev/core: Can not replug device on bus that allows one device | expand |
On Mon, 10 Dec 2018 14:14:14 -0500 Tony Krowiak <akrowiak@linux.ibm.com> wrote: > If the maximum number of devices allowed on a bus is 1 and a device > which is plugged into the bus is subsequently unplugged, attempting to replug > the device fails with error "Bus 'xxx' does not support hotplugging". > The "error" is detected in the qbus_is_full(BusState *bus) function > (qdev_monitor.c) because bus->max_index >= bus_class->max_dev. The > root of the problem is that the bus->max_index is not decremented when a device > is unplugged from the bus. This patch fixes that problem. > > Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> > --- > hw/core/qdev.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index 6b3cc55b27c2..b35b0bf27925 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->max_index--; that might cause problem when bus is allowed to has more than 1 device and unplugged device is not the last one. In that case bus_add_child() might create a child with duplicate name. > + > /* This gives back ownership of kid->child back to us. */ > object_property_del(OBJECT(bus), name, NULL); > object_unref(OBJECT(kid->child));
On 12/11/18 10:23 AM, Igor Mammedov wrote: > On Mon, 10 Dec 2018 14:14:14 -0500 > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > >> If the maximum number of devices allowed on a bus is 1 and a device >> which is plugged into the bus is subsequently unplugged, attempting to replug >> the device fails with error "Bus 'xxx' does not support hotplugging". >> The "error" is detected in the qbus_is_full(BusState *bus) function >> (qdev_monitor.c) because bus->max_index >= bus_class->max_dev. The >> root of the problem is that the bus->max_index is not decremented when a device >> is unplugged from the bus. This patch fixes that problem. >> >> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> >> --- >> hw/core/qdev.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/hw/core/qdev.c b/hw/core/qdev.c >> index 6b3cc55b27c2..b35b0bf27925 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->max_index--; > that might cause problem when bus is allowed to has more than 1 device > and unplugged device is not the last one. > In that case bus_add_child() might create a child with duplicate name. I see what you are saying. The max_index is assigned to the child device index in the bus_add_child() function. The child device index is used to generate a unique name for the child device. The generated name is then used to link the child as a property to the bus. When the child is removed from the bus, the name is regenerated from the child device index and the named property is . It would therefore appear that the real purpose of the max_index is to generate indexes for children of the bus thus ensuring each child has a unique index. In other words, the max_index value is only tangentially connected to indexing the list of children. This results in a disconnect between the usage of the max_index value when adding and removing a child from the bus, and the check in the qbus_is_full() function which compares the max_index to the maximum number of devices allowed on the bus. If a child has been removed from the bus, the max_index value does not indicate whether the bus is full, it only specifies the index to be assigned to the next child to be added to the bus. To resolve this problem, I propose the following: Add the following field to struct BusState (include/hw/qdev_core.h): struct BusState { Object obj; DeviceState *parent; char *name; HotplugHandler *hotplug_handler; int max_index; bool realized; + int num_children; QTAILQ_HEAD(ChildrenHead, BusChild) children; QLIST_ENTRY(BusState) sibling; }; Add the following lines of code to the add/remove child functions in hw/core/qdev.c: static void bus_add_child(BusState *bus, DeviceState *child) { char name[32]; BusChild *kid = g_malloc0(sizeof(*kid)); kid->index = bus->max_index++; kid->child = child; object_ref(OBJECT(kid->child)); QTAILQ_INSERT_HEAD(&bus->children, kid, sibling); /* This transfers ownership of kid->child to the property. */ snprintf(name, sizeof(name), "child[%d]", kid->index); object_property_add_link(OBJECT(bus), name, object_get_typename(OBJECT(child)), (Object **)&kid->child, NULL, /* read-only property */ 0, /* return ownership on prop deletion */ NULL); + bus->num_children++; } static void bus_remove_child(BusState *bus, DeviceState *child) { BusChild *kid; QTAILQ_FOREACH(kid, &bus->children, sibling) { if (kid->child == child) { char name[32]; snprintf(name, sizeof(name), "child[%d]", kid->index); QTAILQ_REMOVE(&bus->children, kid, sibling); /* This gives back ownership of kid->child back to us. */ object_property_del(OBJECT(bus), name, NULL); object_unref(OBJECT(kid->child)); g_free(kid); + bus->num_children--; return; } } } Change the line of code in the qbus_is_full() function in qdev_monitor.c: 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; } > >> + >> /* This gives back ownership of kid->child back to us. */ >> object_property_del(OBJECT(bus), name, NULL); >> object_unref(OBJECT(kid->child)); >
On Tue, 11 Dec 2018 14:41:00 -0500 Tony Krowiak <akrowiak@linux.ibm.com> wrote: > On 12/11/18 10:23 AM, Igor Mammedov wrote: > > On Mon, 10 Dec 2018 14:14:14 -0500 > > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > > > >> If the maximum number of devices allowed on a bus is 1 and a device > >> which is plugged into the bus is subsequently unplugged, attempting to replug > >> the device fails with error "Bus 'xxx' does not support hotplugging". > >> The "error" is detected in the qbus_is_full(BusState *bus) function > >> (qdev_monitor.c) because bus->max_index >= bus_class->max_dev. The > >> root of the problem is that the bus->max_index is not decremented when a device > >> is unplugged from the bus. This patch fixes that problem. > >> > >> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> > >> --- > >> hw/core/qdev.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/hw/core/qdev.c b/hw/core/qdev.c > >> index 6b3cc55b27c2..b35b0bf27925 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->max_index--; > > that might cause problem when bus is allowed to has more than 1 device > > and unplugged device is not the last one. > > In that case bus_add_child() might create a child with duplicate name. > > I see what you are saying. The max_index is assigned to the child device > index in the bus_add_child() function. The child device index is used to > generate a unique name for the child device. The generated name is then > used to link the child as a property to the bus. When the child is > removed from the bus, the name is regenerated from the child device > index and the named property is . It would therefore appear that the > real purpose of the max_index is to generate indexes for children of > the bus thus ensuring each child has a unique index. In other words, > the max_index value is only tangentially connected to indexing the list > of children. > > This results in a disconnect between the usage of the max_index value > when adding and removing a child from the bus, and the check in the > qbus_is_full() function which compares the max_index to the maximum > number of devices allowed on the bus. If a child has been removed from > the bus, the max_index value does not indicate whether the bus is > full, it only specifies the index to be assigned to the next child to be > added to the bus. > > To resolve this problem, I propose the following: > > Add the following field to struct BusState (include/hw/qdev_core.h): > > struct BusState { > Object obj; > DeviceState *parent; > char *name; > HotplugHandler *hotplug_handler; > int max_index; > bool realized; > + int num_children; > QTAILQ_HEAD(ChildrenHead, BusChild) children; > QLIST_ENTRY(BusState) sibling; > }; > > Add the following lines of code to the add/remove child functions in > hw/core/qdev.c: > > static void bus_add_child(BusState *bus, DeviceState *child) > { > char name[32]; > BusChild *kid = g_malloc0(sizeof(*kid)); > > kid->index = bus->max_index++; > kid->child = child; > object_ref(OBJECT(kid->child)); > > QTAILQ_INSERT_HEAD(&bus->children, kid, sibling); > > /* This transfers ownership of kid->child to the property. */ > snprintf(name, sizeof(name), "child[%d]", kid->index); > object_property_add_link(OBJECT(bus), name, > object_get_typename(OBJECT(child)), > (Object **)&kid->child, > NULL, /* read-only property */ > 0, /* return ownership on prop deletion */ > NULL); > > + bus->num_children++; > } > > static void bus_remove_child(BusState *bus, DeviceState *child) > { > BusChild *kid; > > QTAILQ_FOREACH(kid, &bus->children, sibling) { > if (kid->child == child) { > char name[32]; > > snprintf(name, sizeof(name), "child[%d]", kid->index); > QTAILQ_REMOVE(&bus->children, kid, sibling); > > /* This gives back ownership of kid->child back to us. */ > object_property_del(OBJECT(bus), name, NULL); > object_unref(OBJECT(kid->child)); > g_free(kid); > > + bus->num_children--; > > return; > } > } > } > > Change the line of code in the qbus_is_full() function in > qdev_monitor.c: > > > 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; > } > looks good to me [...]
On Thu, 13 Dec 2018 13:09:59 +0100 Igor Mammedov <imammedo@redhat.com> wrote: > On Tue, 11 Dec 2018 14:41:00 -0500 > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > > > On 12/11/18 10:23 AM, Igor Mammedov wrote: > > > On Mon, 10 Dec 2018 14:14:14 -0500 > > > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > > > > > >> If the maximum number of devices allowed on a bus is 1 and a device > > >> which is plugged into the bus is subsequently unplugged, attempting to replug > > >> the device fails with error "Bus 'xxx' does not support hotplugging". > > >> The "error" is detected in the qbus_is_full(BusState *bus) function > > >> (qdev_monitor.c) because bus->max_index >= bus_class->max_dev. The > > >> root of the problem is that the bus->max_index is not decremented when a device > > >> is unplugged from the bus. This patch fixes that problem. > > >> > > >> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> > > >> --- > > >> hw/core/qdev.c | 2 ++ > > >> 1 file changed, 2 insertions(+) > > >> > > >> diff --git a/hw/core/qdev.c b/hw/core/qdev.c > > >> index 6b3cc55b27c2..b35b0bf27925 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->max_index--; > > > that might cause problem when bus is allowed to has more than 1 device > > > and unplugged device is not the last one. > > > In that case bus_add_child() might create a child with duplicate name. > > > > I see what you are saying. The max_index is assigned to the child device > > index in the bus_add_child() function. The child device index is used to > > generate a unique name for the child device. The generated name is then > > used to link the child as a property to the bus. When the child is > > removed from the bus, the name is regenerated from the child device > > index and the named property is . It would therefore appear that the > > real purpose of the max_index is to generate indexes for children of > > the bus thus ensuring each child has a unique index. In other words, > > the max_index value is only tangentially connected to indexing the list > > of children. > > > > This results in a disconnect between the usage of the max_index value > > when adding and removing a child from the bus, and the check in the > > qbus_is_full() function which compares the max_index to the maximum > > number of devices allowed on the bus. If a child has been removed from > > the bus, the max_index value does not indicate whether the bus is > > full, it only specifies the index to be assigned to the next child to be > > added to the bus. > > > > To resolve this problem, I propose the following: > > > > Add the following field to struct BusState (include/hw/qdev_core.h): > > > > struct BusState { > > Object obj; > > DeviceState *parent; > > char *name; > > HotplugHandler *hotplug_handler; > > int max_index; > > bool realized; > > + int num_children; > > QTAILQ_HEAD(ChildrenHead, BusChild) children; > > QLIST_ENTRY(BusState) sibling; > > }; > > > > Add the following lines of code to the add/remove child functions in > > hw/core/qdev.c: > > > > static void bus_add_child(BusState *bus, DeviceState *child) > > { > > char name[32]; > > BusChild *kid = g_malloc0(sizeof(*kid)); > > > > kid->index = bus->max_index++; > > kid->child = child; > > object_ref(OBJECT(kid->child)); > > > > QTAILQ_INSERT_HEAD(&bus->children, kid, sibling); > > > > /* This transfers ownership of kid->child to the property. */ > > snprintf(name, sizeof(name), "child[%d]", kid->index); > > object_property_add_link(OBJECT(bus), name, > > object_get_typename(OBJECT(child)), > > (Object **)&kid->child, > > NULL, /* read-only property */ > > 0, /* return ownership on prop deletion */ > > NULL); > > > > + bus->num_children++; > > } > > > > static void bus_remove_child(BusState *bus, DeviceState *child) > > { > > BusChild *kid; > > > > QTAILQ_FOREACH(kid, &bus->children, sibling) { > > if (kid->child == child) { > > char name[32]; > > > > snprintf(name, sizeof(name), "child[%d]", kid->index); > > QTAILQ_REMOVE(&bus->children, kid, sibling); > > > > /* This gives back ownership of kid->child back to us. */ > > object_property_del(OBJECT(bus), name, NULL); > > object_unref(OBJECT(kid->child)); > > g_free(kid); > > > > + bus->num_children--; > > > > return; > > } > > } > > } > > > > Change the line of code in the qbus_is_full() function in > > qdev_monitor.c: > > > > > > 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; > > } > > > > looks good to me > [...] > I agree, the second proposal looks reasonable. Can you send a proper patch so I can r-b it? Halil
On 12/13/18 8:03 AM, Halil Pasic wrote: > On Thu, 13 Dec 2018 13:09:59 +0100 > Igor Mammedov <imammedo@redhat.com> wrote: > >> On Tue, 11 Dec 2018 14:41:00 -0500 >> Tony Krowiak <akrowiak@linux.ibm.com> wrote: >> >>> On 12/11/18 10:23 AM, Igor Mammedov wrote: >>>> On Mon, 10 Dec 2018 14:14:14 -0500 >>>> Tony Krowiak <akrowiak@linux.ibm.com> wrote: >>>> >>>>> If the maximum number of devices allowed on a bus is 1 and a device >>>>> which is plugged into the bus is subsequently unplugged, attempting to replug >>>>> the device fails with error "Bus 'xxx' does not support hotplugging". >>>>> The "error" is detected in the qbus_is_full(BusState *bus) function >>>>> (qdev_monitor.c) because bus->max_index >= bus_class->max_dev. The >>>>> root of the problem is that the bus->max_index is not decremented when a device >>>>> is unplugged from the bus. This patch fixes that problem. >>>>> >>>>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> >>>>> --- >>>>> hw/core/qdev.c | 2 ++ >>>>> 1 file changed, 2 insertions(+) >>>>> >>>>> diff --git a/hw/core/qdev.c b/hw/core/qdev.c >>>>> index 6b3cc55b27c2..b35b0bf27925 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->max_index--; >>>> that might cause problem when bus is allowed to has more than 1 device >>>> and unplugged device is not the last one. >>>> In that case bus_add_child() might create a child with duplicate name. >>> >>> I see what you are saying. The max_index is assigned to the child device >>> index in the bus_add_child() function. The child device index is used to >>> generate a unique name for the child device. The generated name is then >>> used to link the child as a property to the bus. When the child is >>> removed from the bus, the name is regenerated from the child device >>> index and the named property is . It would therefore appear that the >>> real purpose of the max_index is to generate indexes for children of >>> the bus thus ensuring each child has a unique index. In other words, >>> the max_index value is only tangentially connected to indexing the list >>> of children. >>> >>> This results in a disconnect between the usage of the max_index value >>> when adding and removing a child from the bus, and the check in the >>> qbus_is_full() function which compares the max_index to the maximum >>> number of devices allowed on the bus. If a child has been removed from >>> the bus, the max_index value does not indicate whether the bus is >>> full, it only specifies the index to be assigned to the next child to be >>> added to the bus. >>> >>> To resolve this problem, I propose the following: >>> >>> Add the following field to struct BusState (include/hw/qdev_core.h): >>> >>> struct BusState { >>> Object obj; >>> DeviceState *parent; >>> char *name; >>> HotplugHandler *hotplug_handler; >>> int max_index; >>> bool realized; >>> + int num_children; >>> QTAILQ_HEAD(ChildrenHead, BusChild) children; >>> QLIST_ENTRY(BusState) sibling; >>> }; >>> >>> Add the following lines of code to the add/remove child functions in >>> hw/core/qdev.c: >>> >>> static void bus_add_child(BusState *bus, DeviceState *child) >>> { >>> char name[32]; >>> BusChild *kid = g_malloc0(sizeof(*kid)); >>> >>> kid->index = bus->max_index++; >>> kid->child = child; >>> object_ref(OBJECT(kid->child)); >>> >>> QTAILQ_INSERT_HEAD(&bus->children, kid, sibling); >>> >>> /* This transfers ownership of kid->child to the property. */ >>> snprintf(name, sizeof(name), "child[%d]", kid->index); >>> object_property_add_link(OBJECT(bus), name, >>> object_get_typename(OBJECT(child)), >>> (Object **)&kid->child, >>> NULL, /* read-only property */ >>> 0, /* return ownership on prop deletion */ >>> NULL); >>> >>> + bus->num_children++; >>> } >>> >>> static void bus_remove_child(BusState *bus, DeviceState *child) >>> { >>> BusChild *kid; >>> >>> QTAILQ_FOREACH(kid, &bus->children, sibling) { >>> if (kid->child == child) { >>> char name[32]; >>> >>> snprintf(name, sizeof(name), "child[%d]", kid->index); >>> QTAILQ_REMOVE(&bus->children, kid, sibling); >>> >>> /* This gives back ownership of kid->child back to us. */ >>> object_property_del(OBJECT(bus), name, NULL); >>> object_unref(OBJECT(kid->child)); >>> g_free(kid); >>> >>> + bus->num_children--; >>> >>> return; >>> } >>> } >>> } >>> >>> Change the line of code in the qbus_is_full() function in >>> qdev_monitor.c: >>> >>> >>> 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; >>> } >>> >> >> looks good to me >> [...] >> > > I agree, the second proposal looks reasonable. Can you send a proper > patch so I can r-b it? will do > > Halil >
diff --git a/hw/core/qdev.c b/hw/core/qdev.c index 6b3cc55b27c2..b35b0bf27925 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->max_index--; + /* This gives back ownership of kid->child back to us. */ object_property_del(OBJECT(bus), name, NULL); object_unref(OBJECT(kid->child));
If the maximum number of devices allowed on a bus is 1 and a device which is plugged into the bus is subsequently unplugged, attempting to replug the device fails with error "Bus 'xxx' does not support hotplugging". The "error" is detected in the qbus_is_full(BusState *bus) function (qdev_monitor.c) because bus->max_index >= bus_class->max_dev. The root of the problem is that the bus->max_index is not decremented when a device is unplugged from the bus. This patch fixes that problem. Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> --- hw/core/qdev.c | 2 ++ 1 file changed, 2 insertions(+)