Re: [Qemu-devel] [PATCH] qdev: Reset hotplugged devices

[Anthony Liguori]

On 08/26/2010 08:15 AM, Avi Kivity wrote:
>  On 08/25/2010 03:55 PM, Anthony Liguori wrote:
> > > Maybe we can merge the patches.
> > > As for your patch, I have some comment.
> > > - bus itself may want its own handler. At lease pci bus needs it.
> > >    And propagating reset signal to children is up to the bus 
> > > controller.
> >
> > I disagree.  Reset should be equivalent to power off + init and it's 
> > not something that can be selectively propagated.
>
> Not all busses propagate reset - SCSI is an example (I think).

We're talking about cold reset vs. warm reset.

In the absence of passthrough, I'm struggling to see a useful use-case 
with warm reset.  However, there are many useful things we can do 
assuming a cold reset (like MADV_DONTNEED memory on reboot).

That's not saying we shouldn't do a warm reset, but I'd like to see that 
as an incremental addition to what we have today (like introducing a 
propagating warm reset callback) and thinking through what the actual 
behavior should and shouldn't be.

Regards,

Anthony Liguori