hw/ide: Fix crash when plugging a piix3-ide device into the x-remote machine

QEMU currently crashes when the user tries to do something like:

 qemu-system-x86_64 -M x-remote -device piix3-ide

This happens because the "isabus" variable is not initialized with
the x-remote machine yet. Add a proper check for this condition
and propagate the error to the caller, so we can fail there gracefully.

Message-Id: <20210416125256.2039734-1-thuth@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/hw/isa/isa-bus.c b/hw/isa/isa-bus.c
index 7820068e6e..cffaa35e9c 100644
--- a/hw/isa/isa-bus.c
+++ b/hw/isa/isa-bus.c
@@ -131,13 +131,17 @@ void isa_register_ioport(ISADevice *dev, MemoryRegion *io, uint16_t start)
     isa_init_ioport(dev, start);
 }
 
-void isa_register_portio_list(ISADevice *dev,
-                              PortioList *piolist, uint16_t start,
-                              const MemoryRegionPortio *pio_start,
-                              void *opaque, const char *name)
+int isa_register_portio_list(ISADevice *dev,
+                             PortioList *piolist, uint16_t start,
+                             const MemoryRegionPortio *pio_start,
+                             void *opaque, const char *name)
 {
     assert(piolist && !piolist->owner);
 
+    if (!isabus) {
+        return -ENODEV;
+    }
+
     /* START is how we should treat DEV, regardless of the actual
        contents of the portio array.  This is how the old code
        actually handled e.g. the FDC device.  */
@@ -145,6 +149,8 @@ void isa_register_portio_list(ISADevice *dev,
 
     portio_list_init(piolist, OBJECT(dev), pio_start, opaque, name);
     portio_list_add(piolist, isabus->address_space_io, start);
+
+    return 0;
 }
 
 static void isa_device_init(Object *obj)