[PATCH] vga: don't abort when adding a duplicate isa-vga device

["Jose R. Ziviani" <jziviani@suse.de>]

If users try to add an isa-vga device that was already registered,
still in command line, qemu will crash:

$ qemu-system-mips64el -M pica61 -device isa-vga
RAMBlock "vga.vram" already registered, abort!
Aborted (core dumped)

That particular board registers such device automaticaly, so it's
not obvious that a VGA device already exists. This patch changes
this behavior by displaying a message and ignoring that device,
starting qemu normally.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/44
Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
---
 hw/display/vga-isa.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/hw/display/vga-isa.c b/hw/display/vga-isa.c
index 90851e730b..69db502dde 100644
--- a/hw/display/vga-isa.c
+++ b/hw/display/vga-isa.c
@@ -61,6 +61,15 @@ static void vga_isa_realizefn(DeviceState *dev, Error **errp)
     MemoryRegion *vga_io_memory;
     const MemoryRegionPortio *vga_ports, *vbe_ports;
 
+    /*
+     * some machines register VGA by default, so instead of aborting
+     * it, show a message and ignore this device.
+     */
+    if (qemu_ram_block_by_name("vga.vram")) {
+        error_report("vga.vram is already registered, ignoring this device");
+        return;
+    }
+
     s->global_vmstate = true;
     vga_common_init(s, OBJECT(dev));
     s->legacy_address_space = isa_address_space(isadev);
-- 
2.32.0