Re: Remaining passthrough/VT-d tasks list

[Amit Shah <amit.shah@redhat.com>]

* On Wednesday 24 Sep 2008 14:08:14 Han, Weidong wrote:
> Amit Shah wrote:
> > * On Wednesday 24 Sep 2008 13:21:25 Han, Weidong wrote:
> >> Amit Shah wrote:
> >>>>         - Add dummy driver to hide/unbind passthrough device from
> >>>> host kernel
> >>>
> >>> This isn't needed; we currently don't assign the device to the guest
> >>> if we find that a driver is already loaded. I intend to change it to
> >>> failing guest start altogether in case we find a module already
> >>> using a device. When a guest exits, we release all the structures
> >>> and hence even unloading kvm is not needed to reclaim the device on
> >>> the host side.
> >>
> >> This task needn't targe 2.6.28. For long term, we need it to make
> >> device assignment more user friendly.
> >
> > How is the current scheme not user friendly? Or, how will adding a
> > "dummy driver" be more user friendly?
>
> We had some discussion on this few months ago. Currently, users need to
> remove device driver before assignment. If there are more than one same
> type devices, removing driver makes them cannot work at the same time,
> even though user just want to assign one of them to guest. Note that not
> all drivers support unbind function. If we can provide a mechanism to
> hide single device independently, e.g, implement a dummy driver to own
> devices that user want to assign to guest. I think it's more friendly to
> end user than remove/unbind driver manually.

This needs a change in the driver core and it definitely won't be solved by 
having a dummy device. We have to have a way to signal to modules that a 
particular device will now be owned by a different module, even if the 
current module thinks it is the sole owner.