[SeaBIOS] [PATCH] Support more than one vga card

Anthony Liguori aliguori at us.ibm.com
Wed May 4 18:51:02 CEST 2011

On 05/04/2011 11:22 AM, Glauber Costa wrote:
> On Tue, 2011-05-03 at 20:51 -0400, Kevin O'Connor wrote:
>> On Tue, May 03, 2011 at 09:41:48PM -0300, Glauber Costa wrote:
>>> On Tue, 2011-05-03 at 19:58 -0400, Kevin O'Connor wrote:
>>>> My understanding is that in a machine with multiple VGA devices only
>>>> one vga device is setup to forward the legacy VGA IO ranges over PCI,
>>>> and only that device should have its option ROM executed.
>>>> My understanding is that running the vga option roms for all vga
>>>> devices would be incorrect and could cause a real machine to not boot
>>>> properly.
>>> how's that different in pci vs vgaroms/ ?
>>> "Could cause a real machine to not boot" is true regardless.
>> I don't understand your question.  For regular PCI devices every
>> option rom should be run, regardles of how many devices are in the
>> system.  VGA option roms are special though - my understanding is
>> exactly one VGA device should have its option rom executed.
> let me rephrase then: what if you have n vga option roms under fw_cfg's
> vgaroms/ ?
> Would you execute only one of them?

I'm a bit confused.  With sgabios, how is it normally loaded on bare 
metal?  I thought it's often just flashed in a dummy PCI device, make 
part of the BIOS image with a bios editor, or even loaded as part of a 
NICs firmware.

Is it critical that this is loaded as a VGA rom verses a normal option ROM?

The only difference with VGA roms are that they are loaded slightly 
earlier in the process.  You shouldn't lose a lot loading them with 
normal PCI option roms.


Anthony Liguori


More information about the SeaBIOS mailing list