[PATCH v3 12/18] iommu: Add iommu_at[de]tach_device_shared() for multi-device groups

Lu Baolu
2021-12-06T02:01:13Z

The iommu_attach/detach_device() interfaces were exposed for the device
drivers to attach/detach their own domains. The commit <426a273834eae>
("iommu: Limit iommu_attach/detach_device to device with their own group")
restricted them to singleton groups to avoid different device in a group
attaching different domain.

As we've introduced device DMA ownership into the iommu core. We can now
introduce interfaces for muliple-device groups, and "all devices are in the
same address space" is still guaranteed.

The iommu_attach/detach_device_shared() could be used when multiple drivers
sharing the group claim the DMA_OWNER_PRIVATE_DOMAIN ownership. The first
call of iommu_attach_device_shared() attaches the domain to the group.
Other drivers could join it later. The domain will be detached from the
group after all drivers unjoin it.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
---
include/linux/iommu.h | 13 +++++++++
drivers/iommu/iommu.c | 61 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 74 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index afcc07bc8d41..8c81ba11ae8c 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -705,6 +705,8 @@ int iommu_group_set_dma_owner(struct iommu_group *group, enum iommu_dma_owner ow
void *owner_cookie);
void iommu_group_release_dma_owner(struct iommu_group *group, enum iommu_dma_owner owner);
bool iommu_group_dma_owner_unclaimed(struct iommu_group *group);
+int iommu_attach_device_shared(struct iommu_domain *domain, struct device *dev);
+void iommu_detach_device_shared(struct iommu_domain *domain, struct device *dev);

#else /* CONFIG_IOMMU_API */

@@ -745,11 +747,22 @@ static inline int iommu_attach_device(struct iommu_domain *domain,
return -ENODEV;
}

+static inline int iommu_attach_device_shared(struct iommu_domain *domain,
+ struct device *dev)
+{
+ return -ENODEV;
+}
+
static inline void iommu_detach_device(struct iommu_domain *domain,
struct device *dev)
{
}

+static inline void iommu_detach_device_shared(struct iommu_domain *domain,
+ struct device *dev)
+{
+}
+
static inline struct iommu_domain *iommu_get_domain_for_dev(struct device *dev)
{
return NULL;
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 423197db99a9..6dc6e6ad6069 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -50,6 +50,7 @@ struct iommu_group {
struct list_head entry;
enum iommu_dma_owner dma_owner;
refcount_t owner_cnt;
+ refcount_t attach_cnt;
void *owner_cookie;
};

@@ -2026,6 +2027,41 @@ int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
}
EXPORT_SYMBOL_GPL(iommu_attach_device);

+int iommu_attach_device_shared(struct iommu_domain *domain, struct device *dev)
+{
+ struct iommu_group *group;
+ int ret = 0;
+
+ group = iommu_group_get(dev);
+ if (!group)
+ return -ENODEV;
+
+ mutex_lock(&group->mutex);
+ if (refcount_inc_not_zero(&group->attach_cnt)) {
+ if (group->domain != domain ||
+ (group->dma_owner != DMA_OWNER_PRIVATE_DOMAIN &&
+ group->dma_owner != DMA_OWNER_PRIVATE_DOMAIN_USER)) {
+ refcount_dec(&group->attach_cnt);
+ ret = -EBUSY;
+ }
+
+ goto unlock_out;
+ }
+
+ ret = __iommu_attach_group(domain, group);
+ if (ret)
+ goto unlock_out;
+
+ refcount_set(&group->attach_cnt, 1);
+
+unlock_out:
+ mutex_unlock(&group->mutex);
+ iommu_group_put(group);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_attach_device_shared);
+
int iommu_deferred_attach(struct device *dev, struct iommu_domain *domain)
{
const struct iommu_ops *ops = domain->ops;
@@ -2281,6 +2317,31 @@ void iommu_detach_device(struct iommu_domain *domain, struct device *dev)
}
EXPORT_SYMBOL_GPL(iommu_detach_device);

+void iommu_detach_device_shared(struct iommu_domain *domain, struct device *dev)
+{
+ struct iommu_group *group;
+
+ group = iommu_group_get(dev);
+ if (!group)
+ return;
+
+ mutex_lock(&group->mutex);
+ if (WARN_ON(group->domain != domain ||
+ (group->dma_owner != DMA_OWNER_PRIVATE_DOMAIN &&
+ group->dma_owner != DMA_OWNER_PRIVATE_DOMAIN_USER)))
+ goto unlock_out;
+
+ if (refcount_dec_and_test(&group->attach_cnt)) {
+ __iommu_detach_group(domain, group);
+ group->dma_owner = DMA_OWNER_NONE;
+ }
+
+unlock_out:
+ mutex_unlock(&group->mutex);
+ iommu_group_put(group);
+}
+EXPORT_SYMBOL_GPL(iommu_detach_device_shared);
+
struct iommu_domain *iommu_get_domain_for_dev(struct device *dev)
{
struct iommu_domain *domain;
--
2.25.1