Re: [Xen-devel] [PATCH v3 20/24] xen/passthrough: Extend XEN_DOMCTL_assign_device to support DT device

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi,

On 11/03/2015 13:50, Julien Grall wrote:
> On 11/03/2015 12:37, Ian Campbell wrote:
> > On Tue, 2015-03-10 at 16:33 +0000, Julien Grall wrote:
> > > Hi Ian,
> > >
> > > On 20/02/15 17:17, Ian Campbell wrote:
> > > > > +    /* TODO: Do we need to check is_dying? Mostly to protect against
> > > > > +     * hypercall trying to passthrough a device while we are
> > > > > +     * dying.
> > > > FWIW the PCI case appears not to care...
> > > There is one place in XEN_DOMCTL_assign_device...
> > >
> > > Although I don't understand much the usage of is_dying.
> > >
> > > > > +     */
> > > > > +
> > > > > +    switch ( domctl->cmd )
> > > > > +    {
> > > > > +    case XEN_DOMCTL_assign_device:
> > > > > +        ret = -ENOSYS;
> > > > > +        if ( domctl->u.assign_device.dev != XEN_DOMCTL_DEV_DT )
> > > > > +            break;
> > > > You added something similar to iommu_do_pci_domctl, would it not be
> > > > preferable for the caller to switch on domctl->u.assign_device.dev and
> > > > call the correct iommu_do_*_domctl?
> > > I though about it. It would require to stub iommu_do_*_domctl. So I
> > > preferred to chose the current solution.
> > You mean iommu_do_{pci,dt}_domctl?
> >
> > IIRC you already added suitable #defines for when these features are
> > present, so reusing them at the call sites wouldn't be too bad, or else
> > stubs aren't the worst thing either.
> Hmmm I think I got you point now. Do you mean have something like:
>
> switch (domctl->u.assign_device.dev)
> {
> #ifdef HAS_PCI
> case XEN_DOMCTL_DEV_PCI:
>      ret = iommu_do_pci_domctl();
>      break;
> #endif
> #ifdef HAS_DEVICE_TREE
> case XEN_DOMCTL_DEV_DT:
>      ret = iommu_do_dt_domctl()
>      break;
> #endif
>
> default:
>     ret = -ENOSYS;
> }
I though more about it and it won't be possible to do it unless we 
decode DOMCTL too.
This is because the DOMCTL_get_device_group use a different structure 
and is only for PCI.
So unless we decide to consolidate the 2 DOMCTL structures in a single 
one. I would prefer to keep the current solution with the suggestion 
made by Jan earlier.
Regards,

--
Julien Grall

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