Re: [Qemu-devel] [4261] Errors while registering ioports are not fatal (Glauber Costa).

[Anthony Liguori]

andrzej zaborowski wrote:
> On 26/04/2008, Paul Brook <address@hidden> wrote:
>   
> > On Saturday 26 April 2008, Andrzej Zaborowski wrote:
> >  > Revision: 4261
> >  >           http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=4261
> >  > Author:   balrog
> >  > Date:     2008-04-26 16:04:29 +0000 (Sat, 26 Apr 2008)
> >  >
> >  > Log Message:
> >  > -----------
> >  > Errors while registering ioports are not fatal (Glauber Costa).
> >
> >  Why shouldn't they be fatal? How can this be anything other than a serious bug
> >  in the device emulation?
> >     
>
> This change is perhaps not useful, it would be useful with hot-plugged
> / proxied pci devices.  I think they are desirable features. But the
> patchsets submitted turn out to depend on too much kvm code to ever
> work alone so I might just as well revert :(
>   

It's not at all kvm specific.  Even if QEMU never merged PCI hotplug 
(although I see no reason why not to), it's the right direction to move 
toward.

In the future, if we add configuration files to specific the hardware 
associated with a machine, you want to be able to gracefully detect when 
a configuration file results in IO port conflicts.  Just exiting deep 
within register_ioport() is the wrong approach as a user will never know 
what the problem was.

Being able to propagate the error gives the configuration parsing 
routines an opportunity to present a more human readable error like 
"cannot add device 'blah' because of conflict IO port range with device 
'foo'".

Regards,

Anthony Liguori

> You might not want qemu to quit a running session if it's possible to
> continue running, even if there turns out to be a serious bug.
>
> Regards
>
>
>