Re: [RFC v2 8/9] KVM: KVM-VFIO: generic KVM_DEV_VFIO_DEVICE command and IRQ forwarding control

Christoffer Dall
2014-09-11T21:59:53Z

On Thu, Sep 11, 2014 at 12:14:10PM -0600, Alex Williamson wrote:
> On Thu, 2014-09-11 at 19:10 +0200, Christoffer Dall wrote:
> > On Wed, Sep 10, 2014 at 11:05:49PM -0600, Alex Williamson wrote:
> > > On Thu, 2014-09-11 at 05:10 +0200, Christoffer Dall wrote:
> > > > On Mon, Sep 01, 2014 at 02:52:47PM +0200, Eric Auger wrote:
> >
> > [...]
> >
> > > > >
> > > > > +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_FORWARD
> > > > > +int kvm_arch_set_fwd_state(struct kvm_fwd_irq *pfwd,
> > > >
> > > > what's the 'p' in pfwd?
> > >
> > > p is for pointer?
> > >
> >
> > shouldn't the type declation spell out quite clearly to me that I'm
> > dealing with a pointer?
>
> Sure. In the cases where I've done similar things it's more a matter of
> not needing to come up with another variable, for instance if I need
> both a struct and a struct* I might call them foo and pfoo if I can't
> come up with anything more meaningful.
>
>
> > [...]
> >
> > > >
> > > > need some spaceing here, also, I would turn this around, first check if
> > > > the strcmp fails, and then error out, then do you next check etc., to
> > > > avoid so many nested statements.
> > > >
> > > > > + /* is a ref to this device already owned by the KVM-VFIO device? */
> > > >
> > > > this comment is not particularly helpful in its current form, it would
> > > > be helpful if you specified that we're checking whether that particular
> > > > device/irq combo is already registered.
> > > >
> > > > > + *kvm_vdev = kvm_vfio_find_device(kv, vdev);
> > > > > + if (*kvm_vdev) {
> > > > > + if (kvm_vfio_find_irq(*kvm_vdev, fwd_irq->index)) {
> > > > > + kvm_err("%s irq %d already forwarded\n",
> > > > > + __func__, *hwirq);
> > >
> > > Why didn't we do this first?
> > >
> > huh?
>
> The code is doing:
>
> 1. can the arch forward this irq
> 2. are we already forwarding this irq
>
> It's backwards, test for duplicates locally before calling out into arch
> code. Besides, I think the arch code here should go away and just be
> another error condition for the call-out. Thanks,
>
Ah, right, you meant for the whole check. I agree completely.

-Christoffer