vga: Allow writing VBE_DISPI_ID5 to ID register

The highest VBE_DISPI_INDEX_ID version supported by QEMU is
VBE_DISPI_ID5. But currently QEMU only allows writing values up to
VBE_DISPI_ID4 to the VBE_DISPI_INDEX_ID register.

As a result of this when a lower version is written to this register and
later VBE_DISPI_ID5 is written back, reads from the register will
continue to report the lower version.

Indeed SeaBIOS is doing that during VGA initialization which causes
guests to always read VBE_DISPI_ID0 instead of the correct version.

Signed-off-by: Dennis Wölfing <denniswoelfing@gmx.de>
Message-Id: <20210607115303.228659-1-denniswoelfing@gmx.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/hw/display/vga.c b/hw/display/vga.c
index 28a90e30d0cf76b13d8f7e653286b5ad9f03f7e9..9d1f66af402e54103033dc90c6589339fd199d8e 100644 (file)
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -752,7 +752,8 @@ void vbe_ioport_write_data(void *opaque, uint32_t addr, uint32_t val)
                 val == VBE_DISPI_ID1 ||
                 val == VBE_DISPI_ID2 ||
                 val == VBE_DISPI_ID3 ||
-                val == VBE_DISPI_ID4) {
+                val == VBE_DISPI_ID4 ||
+                val == VBE_DISPI_ID5) {
                 s->vbe_regs[s->vbe_index] = val;
             }
             break;