Messages in this thread | | | Subject | Re: [PATCH] iommu/of: Fix of_iommu_configure() for disabled IOMMUs | From | Robin Murphy <> | Date | Fri, 4 Aug 2017 15:44:53 +0100 |
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On 04/08/17 12:16, Robin Murphy wrote: > Sudeep reports that the logic is slightly broken when a PCI iommu-map > entry targets an IOMMU marked as disabled in DT, since of_pci_map_rid() > succeeds in following a phandle, and of_iommu_xlate() doesn't return an > error value, but we miss checking whether ops was actually non-NULL. > Whilst this could be solved with a point fix in of_pci_iommu_init(), it > suggests that all the juggling of ERR_PTR values through the ops pointer > is proving rather too complicated for its own good, so let's instead > simplify the whole flow (with a side-effect of eliminating the cause of > the bug). > > The fact that we now rely on iommu_fwspec means that we no longer need > to pass around an iommu_ops pointer at all - we can simply propagate a > regular int return value until we know whether we have a viable IOMMU, > then retrieve the ops from the fwspec if and when we actually need them. > This makes everything a bit more uniform and certainly easier to follow. > > Reported-by: Sudeep Holla <sudeep.holla@arm.com> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > > This could be squashed into the currently-queued offender, but if not, > Fixes: d87beb749281 ("iommu/of: Handle PCI aliases properly") > > Robin. > > drivers/iommu/of_iommu.c | 63 ++++++++++++++++++++++++------------------------ > 1 file changed, 31 insertions(+), 32 deletions(-) > > diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c > index be8ac1ddec06..198ef9a49f64 100644 > --- a/drivers/iommu/of_iommu.c > +++ b/drivers/iommu/of_iommu.c > @@ -25,6 +25,8 @@ > #include <linux/of_pci.h> > #include <linux/slab.h> > > +#define NO_IOMMU 1 > + > static const struct of_device_id __iommu_of_table_sentinel > __used __section(__iommu_of_table_end); > > @@ -109,8 +111,8 @@ static bool of_iommu_driver_present(struct device_node *np) > return of_match_node(&__iommu_of_table, np); > } > > -static const struct iommu_ops > -*of_iommu_xlate(struct device *dev, struct of_phandle_args *iommu_spec) > +static int of_iommu_xlate(struct device *dev, > + struct of_phandle_args *iommu_spec) > { > const struct iommu_ops *ops; > struct fwnode_handle *fwnode = &iommu_spec->np->fwnode; > @@ -120,24 +122,20 @@ static const struct iommu_ops > if ((ops && !ops->of_xlate) || > !of_device_is_available(iommu_spec->np) || > (!ops && !of_iommu_driver_present(iommu_spec->np))) > - return NULL; > + return NO_IOMMU; > > err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops); > if (err) > - return ERR_PTR(err); > + return err; > /* > * The otherwise-empty fwspec handily serves to indicate the specific > * IOMMU device we're waiting for, which will be useful if we ever get > * a proper probe-ordering dependency mechanism in future. > */ > if (!ops) > - return ERR_PTR(-EPROBE_DEFER); > + return -EPROBE_DEFER; > > - err = ops->of_xlate(dev, iommu_spec); > - if (err) > - return ERR_PTR(err); > - > - return ops; > + return ops->of_xlate(dev, iommu_spec); > } > > struct of_pci_iommu_alias_info { > @@ -148,7 +146,6 @@ struct of_pci_iommu_alias_info { > static int of_pci_iommu_init(struct pci_dev *pdev, u16 alias, void *data) > { > struct of_pci_iommu_alias_info *info = data; > - const struct iommu_ops *ops; > struct of_phandle_args iommu_spec = { .args_count = 1 }; > int err; > > @@ -156,13 +153,12 @@ static int of_pci_iommu_init(struct pci_dev *pdev, u16 alias, void *data) > "iommu-map-mask", &iommu_spec.np, > iommu_spec.args); > if (err) > - return err == -ENODEV ? 1 : err; > + return err == -ENODEV ? NO_IOMMU : err; > > - ops = of_iommu_xlate(info->dev, &iommu_spec); > + err = of_iommu_xlate(info->dev, &iommu_spec); > of_node_put(iommu_spec.np); > - > - if (IS_ERR(ops)) > - return PTR_ERR(ops); > + if (err) > + return err; > > return info->np == pdev->bus->dev.of_node; > } > @@ -170,9 +166,9 @@ static int of_pci_iommu_init(struct pci_dev *pdev, u16 alias, void *data) > const struct iommu_ops *of_iommu_configure(struct device *dev, > struct device_node *master_np) > { > - const struct iommu_ops *ops = NULL; > + const struct iommu_ops *ops; > struct iommu_fwspec *fwspec = dev->iommu_fwspec; > - int err; > + int err = NO_IOMMU; > > if (!master_np) > return NULL; > @@ -198,10 +194,6 @@ const struct iommu_ops *of_iommu_configure(struct device *dev, > > err = pci_for_each_dma_alias(to_pci_dev(dev), > of_pci_iommu_init, &info); > - if (err) /* err > 0 means the walk stopped, but non-fatally */ > - ops = ERR_PTR(min(err, 0)); > - else /* success implies both fwspec and ops are now valid */ > - ops = dev->iommu_fwspec->ops; > } else { > struct of_phandle_args iommu_spec; > int idx = 0; > @@ -209,28 +201,35 @@ const struct iommu_ops *of_iommu_configure(struct device *dev, > while (!of_parse_phandle_with_args(master_np, "iommus", > "#iommu-cells", > idx, &iommu_spec)) { > - ops = of_iommu_xlate(dev, &iommu_spec); > + err = of_iommu_xlate(dev, &iommu_spec); > of_node_put(iommu_spec.np); > idx++; > - if (IS_ERR_OR_NULL(ops)) > + if (err) > break; > } > } > + > + /* > + * Two success conditions are represented by non-negative err here: > + * >0 : there is no IOMMU, or one was unavailable for non-fatal reasons > + * 0 : we found an IOMMU, and dev->fwspec is initialised appropriately > + * <0 : any actual error > + */ > + if (err > 0) > + return NULL; > + > /* > * If we have reason to believe the IOMMU driver missed the initial > * add_device callback for dev, replay it to get things in order. > */ > - if (!IS_ERR_OR_NULL(ops) && ops->add_device && > - dev->bus && !dev->iommu_group) { > + ops = dev->iommu_fwspec->ops; > + if (!err && ops->add_device && dev->bus && !dev->iommu_group) > err = ops->add_device(dev); > - if (err) > - ops = ERR_PTR(err); > - } > > /* Ignore all other errors apart from EPROBE_DEFER */ > - if (IS_ERR(ops) && (PTR_ERR(ops) != -EPROBE_DEFER)) { > - dev_dbg(dev, "Adding to IOMMU failed: %ld\n", PTR_ERR(ops)); > - ops = NULL; > + if (err && err != -EPROBE_DEFER) { > + dev_dbg(dev, "Adding to IOMMU failed: %d\n", err); > + return NULL; > }
Ugh, no, now we fail to pass -EPROBE_DEFER properly (turns out my test device was also deferring for other reasons and getting lucky). I really am starting to hate ERR_PTRs...
v2 coming shortly, sorry.
Robin.
> > return ops; >
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