On 1/7/22 1:06 AM, Jason Gunthorpe wrote:
On Thu, Jan 06, 2022 at 10:20:46AM +0800, Lu Baolu wrote:
Expose an interface to replace the domain of an iommu group for frameworks
like vfio which claims the ownership of the whole iommu group.
Signed-off-by: Lu Baolu <[email protected]>
include/linux/iommu.h | 10 ++++++++++
drivers/iommu/iommu.c | 37 +++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 408a6d2b3034..66ebce3d1e11 100644
+++ b/include/linux/iommu.h
@@ -677,6 +677,9 @@ void iommu_device_unuse_dma_api(struct device *dev);
int iommu_group_set_dma_owner(struct iommu_group *group, void *owner);
void iommu_group_release_dma_owner(struct iommu_group *group);
bool iommu_group_dma_owner_claimed(struct iommu_group *group);
+int iommu_group_replace_domain(struct iommu_group *group,
+ struct iommu_domain *old,
+ struct iommu_domain *new);
#else /* CONFIG_IOMMU_API */
@@ -1090,6 +1093,13 @@ static inline bool iommu_group_dma_owner_claimed(struct iommu_group *group)
{
return false;
}
+
+static inline int
+iommu_group_replace_domain(struct iommu_group *group, struct iommu_domain *old,
+ struct iommu_domain *new)
+{
+ return -ENODEV;
+}
#endif /* CONFIG_IOMMU_API */
/**
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 72a95dea688e..ab8ab95969f5 100644
+++ b/drivers/iommu/iommu.c
@@ -3431,3 +3431,40 @@ bool iommu_group_dma_owner_claimed(struct iommu_group
*group)
return user;
}
EXPORT_SYMBOL_GPL(iommu_group_dma_owner_claimed);
+
+/**
+ * iommu_group_replace_domain() - Replace group's domain
+ * @group: The group.
+ * @old: The previous attached domain. NULL for none.
+ * @new: The new domain about to be attached.
+ *
+ * This is to support backward compatibility for vfio which manages the dma
+ * ownership in iommu_group level.
This should mention it can only be used with iommu_group_set_dma_owner()
Sure.
+ if (old)
+ __iommu_detach_group(old, group);
+
+ if (new) {
+ ret = __iommu_attach_group(new, group);
+ if (ret && old)
+ __iommu_attach_group(old, group);
+ }
The sketchy error unwind here gives me some pause for sure. Maybe we
should define that on error this leaves the domain as NULL
Complicates vfio a tiny bit to cope with this failure but seems
cleaner than leaving it indeterminate.
Fair enough.
Jason
Best regards,
baolu
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