[PATCH v2 5/8] iommu: Switch __iommu_domain_alloc() to device ops

Robin Murphy
2023-01-26T18:26:47Z

In all the places we allocate default domains, we have (or can easily
get hold of) a device from which to resolve the right IOMMU ops; only
the public iommu_domain_alloc() interface actually depends on bus ops.
Reworking the public API is a big enough mission in its own right, but
in the meantime we can still decouple it from bus ops internally to move
forward.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---

v2: - Explain the mitigation better in the warning message
- Fix theoretical bug if alloc_dev is never assigned because the
bus has no devices
- Use new dev_iommu_ops_valid() since in theory VFIO noiommu makes
device_iommu_mapped() -> dev_iommu_ops() an unsafe assumption
[Baolu]

drivers/iommu/iommu.c | 59 ++++++++++++++++++++++++++++---------------
1 file changed, 39 insertions(+), 20 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 440bb3b7bded..bdc5fdf39d2b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -89,7 +89,7 @@ static int iommu_bus_notifier(struct notifier_block *nb,
unsigned long action, void *data);
static int iommu_alloc_default_domain(struct iommu_group *group,
struct device *dev);
-static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+static struct iommu_domain *__iommu_domain_alloc(struct device *dev,
unsigned type);
static int __iommu_attach_device(struct iommu_domain *domain,
struct device *dev);
@@ -1641,15 +1641,15 @@ static int iommu_get_def_domain_type(struct device *dev)
return 0;
}

-static int iommu_group_alloc_default_domain(struct bus_type *bus,
- struct iommu_group *group,
+static int iommu_group_alloc_default_domain(struct iommu_group *group,
+ struct device *dev,
unsigned int type)
{
struct iommu_domain *dom;

- dom = __iommu_domain_alloc(bus, type);
+ dom = __iommu_domain_alloc(dev, type);
if (!dom && type != IOMMU_DOMAIN_DMA) {
- dom = __iommu_domain_alloc(bus, IOMMU_DOMAIN_DMA);
+ dom = __iommu_domain_alloc(dev, IOMMU_DOMAIN_DMA);
if (dom)
pr_warn("Failed to allocate default IOMMU domain of type %u for group %s - Falling back to IOMMU_DOMAIN_DMA",
type, group->name);
@@ -1674,7 +1674,7 @@ static int iommu_alloc_default_domain(struct iommu_group *group,

type = iommu_get_def_domain_type(dev) ? : iommu_def_domain_type;

- return iommu_group_alloc_default_domain(dev->bus, group, type);
+ return iommu_group_alloc_default_domain(group, dev, type);
}

/**
@@ -1787,8 +1787,7 @@ static int probe_get_default_domain_type(struct device *dev, void *data)
return 0;
}

-static void probe_alloc_default_domain(struct bus_type *bus,
- struct iommu_group *group)
+static void probe_alloc_default_domain(struct iommu_group *group)
{
struct __group_domain_type gtype;

@@ -1798,10 +1797,12 @@ static void probe_alloc_default_domain(struct bus_type *bus,
__iommu_group_for_each_dev(group, &gtype,
probe_get_default_domain_type);

- if (!gtype.type)
+ if (!gtype.type) {
gtype.type = iommu_def_domain_type;
+ gtype.dev = iommu_group_first_dev(group);
+ }

- iommu_group_alloc_default_domain(bus, group, gtype.type);
+ iommu_group_alloc_default_domain(group, gtype.dev, gtype.type);

}

@@ -1864,7 +1865,7 @@ int bus_iommu_probe(struct bus_type *bus)
list_del_init(&group->entry);

/* Try to allocate default domain */
- probe_alloc_default_domain(bus, group);
+ probe_alloc_default_domain(group);

if (!group->default_domain) {
mutex_unlock(&group->mutex);
@@ -1953,15 +1954,12 @@ void iommu_set_fault_handler(struct iommu_domain *domain,
}
EXPORT_SYMBOL_GPL(iommu_set_fault_handler);

-static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+static struct iommu_domain *__iommu_domain_alloc(struct device *dev,
unsigned type)
{
- const struct iommu_ops *ops = bus ? bus->iommu_ops : NULL;
+ const struct iommu_ops *ops = dev_iommu_ops(dev);
struct iommu_domain *domain;

- if (!ops)
- return NULL;
-
domain = ops->domain_alloc(type);
if (!domain)
return NULL;
@@ -1980,9 +1978,30 @@ static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
return domain;
}

+static int __iommu_domain_alloc_dev(struct device *dev, void *data)
+{
+ struct device **alloc_dev = data;
+
+ if (!dev_iommu_ops_valid(dev))
+ return 0;
+
+ WARN_ONCE(*alloc_dev && dev_iommu_ops(dev) != dev_iommu_ops(*alloc_dev),
+ "Multiple IOMMU drivers present, which the public IOMMU API can't fully support yet. You may still need to disable one or more to get the expected result here, sorry!\n");
+
+ *alloc_dev = dev;
+ return 0;
+}
+
struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
{
- return __iommu_domain_alloc(bus, IOMMU_DOMAIN_UNMANAGED);
+ struct device *dev = NULL;
+
+ /* We always check the whole bus, so the return value isn't useful */
+ bus_for_each_dev(bus, NULL, &dev, __iommu_domain_alloc_dev);
+ if (!dev)
+ return NULL;
+
+ return __iommu_domain_alloc(dev, IOMMU_DOMAIN_UNMANAGED);
}
EXPORT_SYMBOL_GPL(iommu_domain_alloc);

@@ -2906,7 +2925,7 @@ static int iommu_change_dev_def_domain(struct iommu_group *group,
}

/* Sets group->default_domain to the newly allocated domain */
- ret = iommu_group_alloc_default_domain(dev->bus, group, type);
+ ret = iommu_group_alloc_default_domain(group, dev, type);
if (ret)
goto out;

@@ -3120,13 +3139,13 @@ static int __iommu_group_alloc_blocking_domain(struct iommu_group *group)
if (group->blocking_domain)
return 0;

- group->blocking_domain = __iommu_domain_alloc(dev->bus, IOMMU_DOMAIN_BLOCKED);
+ group->blocking_domain = __iommu_domain_alloc(dev, IOMMU_DOMAIN_BLOCKED);
if (!group->blocking_domain) {
/*
* For drivers that do not yet understand IOMMU_DOMAIN_BLOCKED
* create an empty domain instead.
*/
- group->blocking_domain = __iommu_domain_alloc(dev->bus, IOMMU_DOMAIN_UNMANAGED);
+ group->blocking_domain = __iommu_domain_alloc(dev, IOMMU_DOMAIN_UNMANAGED);
if (!group->blocking_domain)
return -EINVAL;
}
--
2.36.1.dirty