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Commit da4b0275 authored by Robin Murphy's avatar Robin Murphy Committed by Joerg Roedel
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iommu/of: Fix of_iommu_configure() for disabled IOMMUs 



Sudeep reports that the logic got 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.

Fixes: d87beb74 ("iommu/of: Handle PCI aliases properly")
Reported-by: default avatarSudeep Holla <sudeep.holla@arm.com>
Tested-by: default avatarSudeep Holla <sudeep.holla@arm.com>
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 05f80300

drivers/iommu/of_iommu.c

+29 −30
Original line number Diff line number Diff line
@@ -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;

}
@@ -172,7 +168,7 @@ const struct iommu_ops *of_iommu_configure(struct device *dev, 
{

	const struct iommu_ops *ops = NULL;

	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;
@@ -209,27 +201,34 @@ 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 can be 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)

		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.

	 */

	if (!IS_ERR_OR_NULL(ops) && ops->add_device &&

	    dev->bus && !dev->iommu_group) {

	if (ops && 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));

	if (err == -EPROBE_DEFER) {

		ops = ERR_PTR(err);

	} else if (err < 0) {

		dev_dbg(dev, "Adding to IOMMU failed: %d\n", err);

		ops = NULL;

	}