[PATCH v4 01/10] iommu: Introduce a replace API for device pasid

[Yi Liu <yi.l.liu@intel.com>]

Provide a high-level API to allow replacements of one domain with
another for specific pasid of a device. This is similar to
iommu_group_replace_domain() and it is expected to be used only by
IOMMUFD.

Co-developed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
 drivers/iommu/iommu-priv.h |  4 ++
 drivers/iommu/iommu.c      | 90 ++++++++++++++++++++++++++++++++++++--
 2 files changed, 90 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommu-priv.h b/drivers/iommu/iommu-priv.h
index de5b54eaa8bf..90b367de267e 100644
--- a/drivers/iommu/iommu-priv.h
+++ b/drivers/iommu/iommu-priv.h
@@ -27,6 +27,10 @@ static inline const struct iommu_ops *iommu_fwspec_ops(struct iommu_fwspec *fwsp
 int iommu_group_replace_domain(struct iommu_group *group,
 			       struct iommu_domain *new_domain);
 
+int iommu_replace_device_pasid(struct iommu_domain *domain,
+			       struct device *dev, ioasid_t pasid,
+			       struct iommu_attach_handle *handle);
+
 int iommu_device_register_bus(struct iommu_device *iommu,
 			      const struct iommu_ops *ops,
 			      const struct bus_type *bus,
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index b6b44b184004..066f659018a5 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3347,14 +3347,15 @@ static void iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid,
 }
 
 static int __iommu_set_group_pasid(struct iommu_domain *domain,
-				   struct iommu_group *group, ioasid_t pasid)
+				   struct iommu_group *group, ioasid_t pasid,
+				   struct iommu_domain *old)
 {
 	struct group_device *device, *last_gdev;
 	int ret;
 
 	for_each_group_device(group, device) {
 		ret = domain->ops->set_dev_pasid(domain, device->dev,
-						 pasid, NULL);
+						 pasid, old);
 		if (ret)
 			goto err_revert;
 	}
@@ -3366,7 +3367,20 @@ static int __iommu_set_group_pasid(struct iommu_domain *domain,
 	for_each_group_device(group, device) {
 		if (device == last_gdev)
 			break;
-		iommu_remove_dev_pasid(device->dev, pasid, domain);
+		/* If no old domain, undo the succeeded devices/pasid */
+		if (!old) {
+			iommu_remove_dev_pasid(device->dev, pasid, domain);
+			continue;
+		}
+
+		/*
+		 * Rollback the succeeded devices/pasid to the old domain.
+		 * And it is a driver bug to fail attaching with a previously
+		 * good domain.
+		 */
+		if (WARN_ON(old->ops->set_dev_pasid(old, device->dev,
+						    pasid, domain)))
+			iommu_remove_dev_pasid(device->dev, pasid, domain);
 	}
 	return ret;
 }
@@ -3425,7 +3439,7 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
 	if (ret)
 		goto out_unlock;
 
-	ret = __iommu_set_group_pasid(domain, group, pasid);
+	ret = __iommu_set_group_pasid(domain, group, pasid, NULL);
 	if (ret)
 		xa_erase(&group->pasid_array, pasid);
 out_unlock:
@@ -3434,6 +3448,74 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
 }
 EXPORT_SYMBOL_GPL(iommu_attach_device_pasid);
 
+/**
+ * iommu_replace_device_pasid - Replace the domain that a pasid is attached to
+ * @domain: the new iommu domain
+ * @dev: the attached device.
+ * @pasid: the pasid of the device.
+ * @handle: the attach handle.
+ *
+ * This API allows the pasid to switch domains. Return 0 on success, or an
+ * error. The pasid will keep the old configuration if replacement failed.
+ * This is supposed to be used by iommufd, and iommufd can guarantee that
+ * both iommu_attach_device_pasid() and iommu_replace_device_pasid() would
+ * pass in a valid @handle.
+ */
+int iommu_replace_device_pasid(struct iommu_domain *domain,
+			       struct device *dev, ioasid_t pasid,
+			       struct iommu_attach_handle *handle)
+{
+	/* Caller must be a probed driver on dev */
+	struct iommu_group *group = dev->iommu_group;
+	struct iommu_attach_handle *curr;
+	int ret;
+
+	if (!domain->ops->set_dev_pasid)
+		return -EOPNOTSUPP;
+
+	if (!group)
+		return -ENODEV;
+
+	if (!dev_has_iommu(dev) || dev_iommu_ops(dev) != domain->owner ||
+	    pasid == IOMMU_NO_PASID || !handle)
+		return -EINVAL;
+
+	handle->domain = domain;
+
+	mutex_lock(&group->mutex);
+	/*
+	 * The iommu_attach_handle of the pasid becomes inconsistent with the
+	 * actual handle per the below operation. The concurrent PRI path will
+	 * deliver the PRQs per the new handle, this does not have a function
+	 * impact. The PRI path would eventually become consistent when the
+	 * replacement is done.
+	 */
+	curr = (struct iommu_attach_handle *)xa_store(&group->pasid_array,
+						      pasid, handle,
+						      GFP_KERNEL);
+	if (!curr) {
+		xa_erase(&group->pasid_array, pasid);
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	ret = xa_err(curr);
+	if (ret)
+		goto out_unlock;
+
+	if (curr->domain == domain)
+		goto out_unlock;
+
+	ret = __iommu_set_group_pasid(domain, group, pasid, curr->domain);
+	if (ret)
+		WARN_ON(handle != xa_store(&group->pasid_array, pasid,
+					   curr, GFP_KERNEL));
+out_unlock:
+	mutex_unlock(&group->mutex);
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(iommu_replace_device_pasid, IOMMUFD_INTERNAL);
+
 /*
  * iommu_detach_device_pasid() - Detach the domain from pasid of device
  * @domain: the iommu domain.
-- 
2.34.1