[Qemu-devel] Re: Another SIGFPE in display code, now in cirrus

[Avi Kivity]

On 05/12/2010 07:55 PM, Stefano Stabellini wrote:
> > > 3CEh index 26h W(R/W):  BLT Source Pitch                              (5426 +)
> > > bit 0-11  (5426-28) Number of bytes in a scanline at the source.
> > >       0-12  (5429 +)  do
> > >
> > > if the source BLT is supposed to be the number of bytes in a scanline at
> > > the source, then 0 is not a correct value for it.
> > >
> > >        
> > It's useful if you have a one-line horizontal pattern you want to
> > propagate all over.
> >
> >      
>
> It might be useful all right, but it is not entirely clear what the
> hardware should do in this situation from the documentation we have, and
> certainly the current state of the cirrus emulation code doesn't help.
>
> Without any clear indication of what a Cirrus Logic graphic card would
> have done here, I would choose the safest answer that is disregard the
> "delicate" case (if it doesn't break Windows NT).
>    

My guess is that the src or dst address simply doesn't increment.  I 
think it's also fine to ignore the operation completely.

> However I don't mind if we try to handle this case too, provided
> that we handle it well, without SIGFPEs that is :)
>    


--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.