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SubjectRe: [PATCH 3/4] iommu/of: Don't call iommu_ops->add_device directly
Hi Jörg,

On Wed, Dec 19, 2018 at 5:51 PM Joerg Roedel <joro@8bytes.org> wrote:
> On Wed, Dec 19, 2018 at 10:54:18AM +0100, Marek Szyprowski wrote:
> > On 2018-12-11 16:05, Joerg Roedel wrote:
> > > From: Joerg Roedel <jroedel@suse.de>
> > >
> > > Make sure to invoke this call-back through the proper
> > > function of the IOMMU-API.
> > >
> > > Signed-off-by: Joerg Roedel <jroedel@suse.de>
> > > ---
> > > drivers/iommu/of_iommu.c | 6 +++---
> > > 1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> > > index c5dd63072529..4d4847de727e 100644
> > > --- a/drivers/iommu/of_iommu.c
> > > +++ b/drivers/iommu/of_iommu.c
> > > @@ -218,10 +218,10 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
> > > ops = dev->iommu_fwspec->ops;
> > > /*
> > > * If we have reason to believe the IOMMU driver missed the initial
> > > - * add_device callback for dev, replay it to get things in order.
> > > + * probe for dev, replay it to get things in order.
> > > */
> > > - if (ops && ops->add_device && dev->bus && !dev->iommu_group)
> > > - err = ops->add_device(dev);
> > > + if (dev->bus && !dev->iommu_group)
> > > + err = iommu_probe_device(dev);
> >
> > This change removes a check for NULL ops, what causes NULL pointer
> > exception on first device without IOMMU.
>
> Bummer, this check was supposed to be in iommu_probe_device(), but
> apparently it got lost. Does the attached patch fix it?
>
> > I'm also not sure if this is a good idea to call iommu_probe_device(),
> > which comes from dev->bus->iommu_ops, which might be different from ops
> > from local variable.
>
> The local variable comes from dev->iommu_fwspec->ops, which should be
> exactly the same as dev->bus->iommu_ops. I'll leave that for now until
> it turns out to be a problem (which I don't expect).
>
>
> Regards,
>
> Joerg
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index a2131751dcff..3ed4db334341 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -114,10 +114,14 @@ void iommu_device_unregister(struct iommu_device *iommu)
> int iommu_probe_device(struct device *dev)
> {
> const struct iommu_ops *ops = dev->bus->iommu_ops;
> + int ret = -EINVAL;
>
> WARN_ON(dev->iommu_group);
>
> - return ops->add_device(dev);
> + if (ops)

Is this sufficient? The old code checked for ops->add_device != NULL,
too.

> + ret = ops->add_device(dev);
> +
> + return ret;
> }
>
> void iommu_release_device(struct device *dev)


Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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