Re: [Qemu-devel] [PATCH 0/2] virtio: reset all qbuses too when writing to the status field

[Michael S. Tsirkin]

On Mon, Dec 17, 2012 at 04:37:36PM +0100, Paolo Bonzini wrote:
> Il 17/12/2012 16:24, Michael S. Tsirkin ha scritto:
> > On Mon, Dec 17, 2012 at 04:14:00PM +0100, Paolo Bonzini wrote:
> >> Il 17/12/2012 11:40, Michael S. Tsirkin ha scritto:
> >>> How about the following? Then we can put reset
> >>> in generic code where it belongs.
> >>> It's untested - really kind of pseudo code - and
> >>> s390 is still to be updated.
> >>>
> >>> Posting to see what does everyone thinks.
> >>
> >> I'm not (yet) sure how that helps my problem,
> > 
> > It makes it possible for virtio.c to get at the
> > device state through the binding pointer.
> > So you will be able to qdev_reset_all from virtio.c
> > where it belongs, instead of duplicating code
> > in all bindings.
> 
> Yes, but where does it belong?  Do you want to move handling of the
> status register (and others) to hw/virtio.c?

I thought we can have some kind of generic function that all
transports can call. It would call qdev_reset_all internally,
and we would invoke it from all transports.

> Also, you're proposing that I do qdev_reset_all(vdev->binding_opaque)
> but that would be a layering violation.  Generic virtio code should not
> be able to reset the transport-specific setup (e.g. MSIs).
> 
> Paolo

Bus reset looks like this:

        qdev -> pci -> virtio pci reset -> virtio reset

status reset looks like this:

         virtio pci reset -> virtio reset

You original patch was basically calling back to
qdev from virtio pci (bypassing pci).

If that is OK and not a layering violation,
why calling from virtio back to virtio pci not OK?

How do you think reset should be layered?


> >> but it is definitely a
> >> step in the right direction!
> >>
> >> Paolo