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

thanks for the report!

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)
+ ret = ops->add_device(dev);
+
+ return ret;
}

void iommu_release_device(struct device *dev)
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