Re: [Qemu-devel] Standard vga breakage

[Anthony Liguori]

Stefan Weil wrote:
> malc schrieb:
>   
> > On Sun, 15 Nov 2009, Gleb Natapov wrote:
> >
> >     
> > > On Sun, Nov 15, 2009 at 06:22:40PM +0300, malc wrote:
> > >       
> > > > On Sun, 15 Nov 2009, Blue Swirl wrote:
> > > >
> > > >         
> > > > > On Sun, Nov 15, 2009 at 3:25 AM, malc <address@hidden> wrote:
> > > > >           
> > > > > > debian-503-i386-netinst.iso when booted on a machine with `-vga
> > > > > > std' just
> > > > > > shows black screen (after bios' setup screen)
> > > > > >             
> > > > > Just some observations:
> > > > > - if you press enter, installer starts and Linux is able to fix the
> > > > > display
> > > > > - the screen is fine with -bios pcbios.bin, so the issue is related
> > > > > to SeaBIOS
> > > > >           
> > > > Yes i forgot to mention that -bios works, also worth noting is that
> > > > before
> > > > the commit that fixed cirrus -bios hack also made it work.
> > > >         
>
>
> Here is a summary of my analysis of this problem:
>
> Graphics mode memory (ram 0xe0000000 ...) is not mapped
> in QEMU address space (which results in unassigned
> memory writes) for standard pci vga (-vga std), so users
> don't get vga display output with grub (in graphical mode),
> debian installer (in graphical mode) or similar boot software.
>   

0xe00... is the VBE mapping.  The VGABIOS assumes this mapping exists 
when using VBE.  Cirrus doesn't support VBE so it wouldn't be exposed there.

Does the following help:

diff --git a/hw/vga-pci.c b/hw/vga-pci.c
index 479ffb1..e273b8b 100644
--- a/hw/vga-pci.c
+++ b/hw/vga-pci.c
@@ -107,6 +107,12 @@ static int pci_vga_initfn(PCIDevice *dev)
                         PCI_BASE_ADDRESS_MEM_PREFETCH, vga_map);
     }

+#ifdef CONFIG_BOCHS_VBE
+    /* XXX: use optimized standard vga accesses */
+    cpu_register_physical_memory(VBE_DISPI_LFB_PHYSICAL_ADDRESS,
+                                 vga_ram_size, s->vga.vram_offset);
+#endif
+
     /* ROM BIOS */
     rom_add_vga(VGABIOS_FILENAME);
     return 0;

Regards,

Anthony Liguori