[Qemu-devel] [PATCH qemu] pci: Only unmap bus_master_enabled_region if was added previously

[Alexey Kardashevskiy <aik@ozlabs.ru>]

Normally pci_init_bus_master() would be called either via
bus->machine_done.notify or directly from do_pci_register_device().

However if a device's realize() failed, pci_init_bus_master() is not
called, and do_pci_unregister_device() fails on
memory_region_del_subregion() as it was not mapped.

This adds a check that subregion was mapped before unmapping it.

Fixes: c53598ed18e4 ("pci: Add missing drop of bus master AS reference")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
This is to pass iotest 051 which does run QEMU like this:

ppc64-softmmu/qemu-system-ppc64 -nodefaults -machine accel=qtest -nographic -monitor stdio -serial none -drive if=virtio

which normally fails with:

qemu-system-ppc64: -drive if=virtio: Device needs media, but drive is empty

or asserts (without this patch):

qemu-system-ppc64: /home/aik/p/qemu-kvm/memory.c:2118: memory_region_del_subregion: Assertion `subregion->container == mr' failed.
---
 hw/pci/pci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index bd8043c460..259483b1c0 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -869,8 +869,10 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
     pci_dev->bus->devices[pci_dev->devfn] = NULL;
     pci_config_free(pci_dev);
 
-    memory_region_del_subregion(&pci_dev->bus_master_container_region,
-                                &pci_dev->bus_master_enable_region);
+    if (memory_region_is_mapped(&pci_dev->bus_master_enable_region)) {
+        memory_region_del_subregion(&pci_dev->bus_master_container_region,
+                                    &pci_dev->bus_master_enable_region);
+    }
     address_space_destroy(&pci_dev->bus_master_as);
 }
 
-- 
2.11.0