[Qemu-devel] Re: pci: is reset incomplete?

[Anthony Liguori]

Michael S. Tsirkin wrote:
> On Mon, Sep 14, 2009 at 12:15:29PM -0500, Anthony Liguori wrote:
>   
> > Michael S. Tsirkin wrote:
> >     
> > > Hi!
> > > pci bus reset does not seem to clear pci config registers, such as BAR
> > > registers, or memory space enable, of the attached devices: it only
> > > clears the interrupt state.
> > >
> > > This seems wrong, but easy to fix.
> > >   
> > >       
> > I don't think most pci devices reset their config space in their reset  
> > callbacks.
> >     
>
> For things like BAR registers, they really must.
>   

BARs should be registered via pci_register_bar so you should be able to 
centralize their reset.

> class codes are read only registers. Your proposal might be correct for
> some of these. But PCI registers that are reset, change as a result of
> guest activity, and reset values are typically specified by guest spec.
> So I don't think we should let users tweak these.
>   

Well, I guess my general point was that it would be good to add more 
structure to how config space is initialized.  I think a natural 
consequence of that is that it becomes easier to automatically fix the 
values on reset.

Regards,

Anthony Liguori