[Qemu-devel] [PATCH v2] qdev: Keep global allocation counter per bus

[Alexander Graf <agraf@suse.de>]

When we have 2 separate qdev devices that both create a qbus of the
same type without specifying a bus name or device name, we end up
with two buses of the same name, such as ide.0 on the Mac machines:

  dev: macio-ide, id ""
    bus: ide.0
      type IDE
  dev: macio-ide, id ""
    bus: ide.0
      type IDE

If we now spawn a device that connects to a ide.0 the last created
bus gets the device, with the first created bus inaccessible to the
command line.

After some discussion on IRC we concluded that the best quick fix way
forward for this is to make automated bus-class type based allocation
count a global counter. That's what this patch implements. With this
we instead get

  dev: macio-ide, id ""
    bus: ide.1
      type IDE
  dev: macio-ide, id ""
    bus: ide.0
      type IDE

on the example mentioned above.

This also means that if you did -device ...,bus=ide.0 you got a device
on the first bus (the last created one) before this patch and get that
device on the second one (the first created one) now.

This is intended and makes the bus enumeration work as expected.

CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Anthony Liguori <aliguori@amazon.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

---

v1 -> v2:

  - add fix for isapc which was searching for 2 buses called "ide.0"
  - explain the semantic change more in the commit message
---
 hw/core/qdev.c         | 20 +++++++++++++-------
 hw/i386/pc_piix.c      |  8 +++++++-
 include/hw/qdev-core.h |  2 ++
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index e374a93..959130c 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -409,27 +409,33 @@ DeviceState *qdev_find_recursive(BusState *bus, const char *id)
 static void qbus_realize(BusState *bus, DeviceState *parent, const char *name)
 {
     const char *typename = object_get_typename(OBJECT(bus));
+    BusClass *bc;
     char *buf;
-    int i,len;
+    int i, len, bus_id;
 
     bus->parent = parent;
 
     if (name) {
         bus->name = g_strdup(name);
     } else if (bus->parent && bus->parent->id) {
-        /* parent device has id -> use it for bus name */
+        /* parent device has id -> use it plus parent-bus-id for bus name */
+        bus_id = bus->parent->num_child_bus;
+
         len = strlen(bus->parent->id) + 16;
         buf = g_malloc(len);
-        snprintf(buf, len, "%s.%d", bus->parent->id, bus->parent->num_child_bus);
+        snprintf(buf, len, "%s.%d", bus->parent->id, bus_id);
         bus->name = buf;
     } else {
-        /* no id -> use lowercase bus type for bus name */
+        /* no id -> use lowercase bus type plus global bus-id for bus name */
+        bc = BUS_GET_CLASS(bus);
+        bus_id = bc->automatic_ids++;
+
         len = strlen(typename) + 16;
         buf = g_malloc(len);
-        len = snprintf(buf, len, "%s.%d", typename,
-                       bus->parent ? bus->parent->num_child_bus : 0);
-        for (i = 0; i < len; i++)
+        len = snprintf(buf, len, "%s.%d", typename, bus_id);
+        for (i = 0; i < len; i++) {
             buf[i] = qemu_tolower(buf[i]);
+        }
         bus->name = buf;
     }
 
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 4e0dae7..1d02676 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -207,10 +207,16 @@ static void pc_init1(QEMUMachineInitArgs *args,
     } else {
         for(i = 0; i < MAX_IDE_BUS; i++) {
             ISADevice *dev;
+            char busname[] = "ide.0";
             dev = isa_ide_init(isa_bus, ide_iobase[i], ide_iobase2[i],
                                ide_irq[i],
                                hd[MAX_IDE_DEVS * i], hd[MAX_IDE_DEVS * i + 1]);
-            idebus[i] = qdev_get_child_bus(DEVICE(dev), "ide.0");
+            /*
+             * The ide bus name is ide.0 for the first bus and ide.1 for the
+             * second one.
+             */
+            busname[4] = '0' + i;
+            idebus[i] = qdev_get_child_bus(DEVICE(dev), busname);
         }
     }
 
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index f2043a6..09f8527 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -161,6 +161,8 @@ struct BusClass {
     int (*reset)(BusState *bus);
     /* maximum devices allowed on the bus, 0: no limit. */
     int max_dev;
+    /* number of automatically allocated bus ids (e.g. ide.0) */
+    int automatic_ids;
 };
 
 typedef struct BusChild {
-- 
1.8.1.4