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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: d87beb7492 ("iommu/of: Handle PCI aliases properly")
Reported-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Robin Murphy 2017-08-04 17:29:06 +01:00 committed by Joerg Roedel
parent 05f80300dc
commit da4b02750a
1 changed files with 29 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

59
drivers/iommu/of_iommu.c
View File

@ -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;
}