Re: [Qemu-devel] [RFC][PATCH 28/45] qemu-kvm: msix: Drop tracking of used vectors

[Michael S. Tsirkin]

On Fri, Oct 21, 2011 at 11:27:48AM +0200, Jan Kiszka wrote:
> On 2011-10-21 09:54, Michael S. Tsirkin wrote:
> > On Fri, Oct 21, 2011 at 09:09:10AM +0200, Jan Kiszka wrote:
> >> On 2011-10-21 00:02, Michael S. Tsirkin wrote:
> >>>>> Yes. But this still makes an API for acquiring per-vector resources a 
> >>>>> requirement.
> >>>>
> >>>> Yes, but a different one than current use/unuse.
> >>>
> >>> What's wrong with use/unuse as an API? It's already in place
> >>> and virtio calls it.
> >>
> >> Not for that purpose.
> >> It remains a useless API in the absence of KVM's
> >> requirements.
> >>
> > 
> > Sorry, I don't understand. This can acquire whatever resources
> > necessary. It does not seem to make sense to rip it out
> > only to add a different one back in.
> > 
> >>>
> >>>> And it will be an
> >>>> optional one, only for those devices that need to establish irq/eventfd
> >>>> channels.
> >>>>
> >>>> Jan
> >>>
> >>> Not sure this should be up to the device.
> >>
> >> The device provides the fd. At least it acquires and associates it.
> >>
> >> Jan
> > 
> > It would surely be beneficial to be able to have a uniform
> > API so that devices don't need to be recoded to be moved
> > in this way.
> 
> The point is that the current API is useless for devices that do not
> have to declare any vector to the core.

Don't assigned devices want this as well?
They handle 0-address vectors specially, and
this hack absolutely doesn't belong in pci core ...

> By forcing them to call into
> that API, we solve no current problem automatically. We rather need
> associate_vector_with_x (and the reverse). And that only for device that
> have different backends than user space models.
> 
> Jan

I'll need to think about this, would prefer this series not
to get blocked on this issue. We more or less agreed
to add _use_all/unuse_all for now?

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