Re: console font limits

[Kyle Moffett]

On May 03, 2007, at 16:16:51, Jan Engelhardt wrote:
> On May 3 2007 13:15, H. Peter Anvin wrote:
> > Jan Engelhardt wrote:
> > > > Put people didn't like that, and disabled text output when the  
> > > > console is in KD_GRAPHICS mode...
> > >
> > > at the cost of not getting the kernel oops, heh.
> >
> > I thought the reason we didn't display text in KD_GRAPHICS mode  
> > was that KD_GRAPHICS might mean "in a completely different mode  
> > that only userspace knows about."
>
> Hrm. Maybe we need a distinction into KD_KGRAPHICS and KD_UGRAPHICS  
> then.

Actually I think the real problem was that "KD_GRAPHICS" got  
overloaded to mean "some userspace program is probably poking at the  
GPU in very direct ways possibly including /dev/mem".  As such it  
really isn't safe at all for the kernel to write stuff to the screen  
in that situation; you could turn a panic()+reboot-after-30-secs into  
an unrecoverable hard PCI bus lockup.  IIRC there were at least a  
couple chipsets which had that problem with X.  If we can implement  
enough APIs for X to do all of its stuff from userspace without iopl 
() or /dev/mem then we could probably bring back the option for  
dumping oopses to screen in KD_GRAPHICS mode, but otherwise it'll  
just cause more headaches.

Cheers,
Kyle Moffett

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