[SeaBIOS] [PATCH] mark VBE mapping as reserved in e820

Izik Eidus ieidus at redhat.com
Sun Jan 24 01:18:43 CET 2010

On Sat, 23 Jan 2010 19:03:46 -0500
"Kevin O'Connor" <kevin at koconnor.net> wrote:

> On Sun, Jan 24, 2010 at 01:35:21AM +0200, Izik Eidus wrote:
> > On Sat, 23 Jan 2010 18:10:37 -0500
> > "Kevin O'Connor" <kevin at koconnor.net> wrote:
> > > What is special about 0xe0000000 that the OS can't map pci devices
> > > there?  Normal machines don't treat 0xe0000000 as special, why does
> > > the VBE device require that?
> > 
> > From the last time I looked on the code 0xe0000000 was the LFB address,
> > LFB is used by vesa devices as the framebuffer memory area,
> > this mean that vesa devices (not the case for vga) will try to map this
> > 0xe000000 physical memory.
> Okay, but why does the device hardcoded 0xe0000000 - why doesn't it
> use a PCI bar?  A PCI bar should also be sufficient to stop the OS
> from mapping two things to the same address, and it has the advantage
> of not requiring special code in the BIOS.

VESA standard is unrelated to pci devices,
and therefore it can be used with isa devices...

For example spice start the system with the isa device and then only when
there is a driver it move into the QXL device.

I have saw in QA bug that was just this case, windows tryed to map pci device
into the lfb.


> -Kevin

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