Re: [XEN][PATCH v7 11/19] xen/iommu: Introduce iommu_remove_dt_device()

[Vikram Garhwal <vikram.garhwal@amd.com>]

On Mon, Jun 05, 2023 at 08:37:03PM +0100, Julien Grall wrote:
> Hi,
> 
> On 02/06/2023 01:48, Vikram Garhwal wrote:
> > Remove master device from the IOMMU. This will be helpful when removing the
> > overlay nodes using dynamic programming during run time.
> > 
> > Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
> > Reviewed-by: Michal Orzel <michal.orzel@amd.com>
> > Acked-by: Jan Beulich <jbeulich@suse.com>
> > ---
> >   xen/drivers/passthrough/device_tree.c | 41 +++++++++++++++++++++++++++
> >   xen/include/xen/iommu.h               |  2 ++
> >   2 files changed, 43 insertions(+)
> > 
> > diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c
> > index 8cc413f867..301a5bcd97 100644
> > --- a/xen/drivers/passthrough/device_tree.c
> > +++ b/xen/drivers/passthrough/device_tree.c
> > @@ -126,6 +126,47 @@ 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;
> > +
> 
> iommu_add_dt_device() checks if the IOMMU is enabled. I think you should do
> the same here as well and return 0 if it is disabled.
Added iommu_enabled check in v8.
> 
> > +    if ( !ops )
> > +        return -EOPNOTSUPP;
> > +
> > +    spin_lock(&dtdevs_lock);
> > +
> > +    if ( iommu_dt_device_is_assigned_locked(np) )
> > +    {
> > +        rc = -EBUSY;
> > +        goto fail;
> > +    }
> > +
> > +    /*
> > +     * The driver which supports generic IOMMU DT bindings must have this
> > +     * callback implemented.
> > +     */
> 
> It is not clear to me why you want to mandate remove_device when using the
> generic IOMMU DT bindings.
> 
> But if this is really necessary, then I think the comment should be placed
> on top of the callback definition rather than in the caller.
Added a comment on top of remove_generic in smmu.c
> 
> > +    if ( !ops->remove_device )
> > +    {
> > +        rc = -EOPNOTSUPP;
> > +        goto fail;
> > +    }
> > +
> > +    /*
> > +     * Remove master device from the IOMMU if latter is present and available.
> > +     * The driver is responsible for removing is_protected flag.
> > +     */
> > +    rc = ops->remove_device(0, dev);
> > +
> > +    if ( !rc )
> > +        iommu_fwspec_free(dev);
> > +
> > +fail:
> > +    spin_unlock(&dtdevs_lock);
> > +    return rc;
> > +}
> > +
> >   int iommu_add_dt_device(struct dt_device_node *np)
> >   {
> >       const struct iommu_ops *ops = iommu_get_ops();
> > diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
> > index 405db59971..0d7924821b 100644
> > --- a/xen/include/xen/iommu.h
> > +++ b/xen/include/xen/iommu.h
> > @@ -229,6 +229,8 @@ int iommu_release_dt_devices(struct domain *d);
> >    */
> >   int iommu_add_dt_device(struct dt_device_node *np);
> > +int iommu_remove_dt_device(struct dt_device_node *np);
> > +
> >   int iommu_do_dt_domctl(struct xen_domctl *, struct domain *,
> >                          XEN_GUEST_HANDLE_PARAM(xen_domctl_t));
> 
> Cheers,
> 
> -- 
> Julien Grall