Re: [XEN][RFC PATCH v4 09/16] xen/iommu: Introduce iommu_remove_dt_device()

[Julien Grall <julien@xxxxxxx>]

Hi,

On 23/01/2023 10:00, Michal Orzel wrote:
> > Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>
> > ---
> >   xen/drivers/passthrough/device_tree.c | 38 +++++++++++++++++++++++++++
> >   xen/include/xen/iommu.h               |  2 ++
> >   2 files changed, 40 insertions(+)
> >
> > diff --git a/xen/drivers/passthrough/device_tree.c 
> > b/xen/drivers/passthrough/device_tree.c
> > index 457df333a0..a8ba0b0d17 100644
> > --- a/xen/drivers/passthrough/device_tree.c
> > +++ b/xen/drivers/passthrough/device_tree.c
> > @@ -126,6 +126,44 @@ int iommu_release_dt_devices(struct domain *d)
> >       return 0;
> >   }
> >
> > +int iommu_remove_dt_device(struct dt_device_node *np)
> > +{
> > +    const struct iommu_ops *ops = iommu_get_ops();
> > +    struct device *dev = dt_to_dev(np);
> > +    int rc;
> > +
> Aren't we missing a check if iommu is enabled?
>
> > +    if ( !ops )
> > +        return -EOPNOTSUPP;
> -EINVAL to match the return values returned by other functions?
The meaning of -EINVAL is quite overloaded. So it would be better to use 
a mix of errno to help differentiating the error paths.
In this case, '!ops' means there are no possibility (read "support") to 
remove the device. So I think -EOPNOTUSUPP is suitable.
> > +
> > +    spin_lock(&dtdevs_lock);
> > +
> > +    if ( iommu_dt_device_is_assigned_locked(np) ) {
> Incorrect coding style. The closing brace should be placed on the next line.
>
> > +        rc = -EBUSY;
> > +        goto fail;
> > +    }
> > +
> > +    /*
> > +     * The driver which supports generic IOMMU DT bindings must have
> > +     * these callback implemented.
> > +     */
> > +    if ( !ops->remove_device ) {
> Incorrect coding style. The closing brace should be placed on the next line.
>
> > +        rc = -EOPNOTSUPP;
> -EINVAL to match the return values returned by other functions?
Ditto.

Cheers,

--
Julien Grall