[PATCH v10 4/6] iommufd: Add iommufd_access_replace() API

[Nicolin Chen <nicolinc@nvidia.com>]

Taking advantage of the new iommufd_access_change_ioas_id helper, add an
iommufd_access_replace() API for VFIO emulated pathway to use.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/iommufd/device.c | 15 +++++++++++++++
 include/linux/iommufd.h        |  1 +
 2 files changed, 16 insertions(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index e79cbedd8626..7a35503b0123 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -855,6 +855,21 @@ int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id)
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_access_attach, IOMMUFD);
 
+int iommufd_access_replace(struct iommufd_access *access, u32 ioas_id)
+{
+	int rc;
+
+	mutex_lock(&access->ioas_lock);
+	if (!access->ioas) {
+		mutex_unlock(&access->ioas_lock);
+		return -ENOENT;
+	}
+	rc = iommufd_access_change_ioas_id(access, ioas_id);
+	mutex_unlock(&access->ioas_lock);
+	return rc;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_access_replace, IOMMUFD);
+
 /**
  * iommufd_access_notify_unmap - Notify users of an iopt to stop using it
  * @iopt: iopt to work on
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 0ac60256b659..ffc3a949f837 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -49,6 +49,7 @@ iommufd_access_create(struct iommufd_ctx *ictx,
 		      const struct iommufd_access_ops *ops, void *data, u32 *id);
 void iommufd_access_destroy(struct iommufd_access *access);
 int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id);
+int iommufd_access_replace(struct iommufd_access *access, u32 ioas_id);
 void iommufd_access_detach(struct iommufd_access *access);
 
 void iommufd_ctx_get(struct iommufd_ctx *ictx);
-- 
2.41.0