Currently there is no way to distinguish the case that rombar is
explicitly specified as 1 and the case that rombar is not specified.

Set rombar -1 by default to distinguish these cases just as it is done
for addr and romsize. It was confirmed that changing the default value
to -1 will not change the behavior by looking at occurences of rom_bar.

$ git grep -w rom_bar
hw/display/qxl.c:328:    QXLRom *rom = memory_region_get_ram_ptr(&d->rom_bar);
hw/display/qxl.c:431:    qxl_set_dirty(&qxl->rom_bar, 0, qxl->rom_size);
hw/display/qxl.c:1048:    QXLRom *rom = memory_region_get_ram_ptr(&qxl->rom_bar);
hw/display/qxl.c:2131:    memory_region_init_rom(&qxl->rom_bar, OBJECT(qxl), "qxl.vrom",
hw/display/qxl.c:2154: PCI_BASE_ADDRESS_SPACE_MEMORY, &qxl->rom_bar);
hw/display/qxl.h:101:    MemoryRegion       rom_bar;
hw/pci/pci.c:74:    DEFINE_PROP_UINT32("rombar",  PCIDevice, rom_bar, 1),
hw/pci/pci.c:2329:    if (!pdev->rom_bar) {
hw/vfio/pci.c:1019:    if (vdev->pdev.romfile || !vdev->pdev.rom_bar) {
hw/xen/xen_pt_load_rom.c:29:    if (dev->romfile || !dev->rom_bar) {
include/hw/pci/pci_device.h:150:    uint32_t rom_bar;

rom_bar refers to a different variable in qxl. It is only tested if
the value is 0 or not in the other places.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 hw/pci/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 6496d027ca61..47f38375bb09 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -71,7 +71,7 @@ static Property pci_props[] = {
     DEFINE_PROP_PCI_DEVFN("addr", PCIDevice, devfn, -1),
     DEFINE_PROP_STRING("romfile", PCIDevice, romfile),
     DEFINE_PROP_UINT32("romsize", PCIDevice, romsize, -1),
-    DEFINE_PROP_UINT32("rombar",  PCIDevice, rom_bar, 1),
+    DEFINE_PROP_UINT32("rombar",  PCIDevice, rom_bar, -1),
     DEFINE_PROP_BIT("multifunction", PCIDevice, cap_present,
                     QEMU_PCI_CAP_MULTIFUNCTION_BITNR, false),
     DEFINE_PROP_BIT("x-pcie-lnksta-dllla", PCIDevice, cap_present,

-- 
2.43.0