Re: [Qemu-devel] Re: qdev property bug?

[Anthony Liguori]

Michael S. Tsirkin wrote:
> On Mon, Dec 14, 2009 at 09:32:30PM +0100, Gerd Hoffmann wrote:
>   
> > On 12/14/09 21:20, Michael S. Tsirkin wrote:
> >     
> > > > So far, it's not clear to me that anyone has demonstrated how this is
> > > > harmful for people that don't want pxe booting.  Assuming we fix the bug
> > > > about rom loading, then there's really no impact to users.
> > > >         
> > Fix (v2) is on the list already.
> >
> >     
> > > PXE booting might have security impact. You do not want to
> > > do this if you are on a hostile network.
> > >       
> > Option rom loaded doesn't imply pxe boot will be tried.  It only means  
> > PXE boot can be selected, either via
> >
> >   -boot order=[something with 'n' here]
> >
> > or via
> >
> >   -boot menu=on + F12 + picking menu entry
> >
> > By default qemu doesn't try to PXE-boot, even if no other bootable  
> > device is available.
> >
> > cheers,
> >   Gerd
> >     
>
> I guess so. But then, why are we loading it in BIOS
> and wasting memory? Let's only shadow the ROM
> when PXE is selected?
>   

Because it can be selected by the user via the menu and because it can 
be selected at runtime via the boot_set monitor command.

Also, the comment about "wasting memory" not quite accurate.  The memory 
region in question is only used for roms.  If we didn't put roms there, 
it would go to waste.

Currently, the only roms we load are pxe roms or things specified by 
-option-rom.  You could certainly argue that making -option-rom higher 
priority than implicit pxe roms is valuable but removing the pxe roms 
really serves no purpose.

Regards,

Anthony Liguori