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.ho...@arm.com>
Signed-off-by: Robin Murphy <robin.mur...@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;
}
return ops;
--
2.12.2.dirty
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