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

Glauber Costa glommer at redhat.com
Wed May 4 19:05:16 CEST 2011

On Wed, 2011-05-04 at 11:51 -0500, Anthony Liguori wrote:
> 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?

In all my testing, yes.

> 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.

The way it is today, it loses gpxe shell (probably dependent on
execution order), and the boot menu.

If there is anything we care about interaction at boot time, it is those

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