[PATCH v3 6/8] iommufd: IOPF-capable hw page table attach/detach/replace

[Lu Baolu <baolu.lu@linux.intel.com>]

The iopf-capable hw page table attach/detach/replace should use the iommu
iopf-specific interfaces. The pointer to iommufd_device is stored in the
private field of the attachment cookie, so that it can be easily retrieved
in the fault handling paths. The references to iommufd_device and
iommufd_hw_pagetable objects are held until the cookie is released, which
happens after the hw_pagetable is detached from the device and all
outstanding iopf's are responded to. This guarantees that both the device
and hw_pagetable are valid before domain detachment and outstanding faults
are handled.

The iopf-capable hw page tables can only be attached to devices that
support the IOMMU_DEV_FEAT_IOPF feature. On the first attachment of an
iopf-capable hw_pagetable to the device, the IOPF feature is enabled on
the device. Similarly, after the last iopf-capable hwpt is detached from
the device, the IOPF feature is disabled on the device.

The current implementation allows a replacement between iopf-capable and
non-iopf-capable hw page tables. This matches the nested translation use
case, where a parent domain is attached by default and can then be
replaced with a nested user domain with iopf support.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/iommufd/iommufd_private.h |   7 ++
 drivers/iommu/iommufd/device.c          |  15 ++-
 drivers/iommu/iommufd/fault.c           | 122 ++++++++++++++++++++++++
 3 files changed, 141 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 2780bed0c6b1..9844a1289c01 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -398,6 +398,7 @@ struct iommufd_device {
 	/* always the physical device */
 	struct device *dev;
 	bool enforce_cache_coherency;
+	bool iopf_enabled;
 	/* outstanding faults awaiting response indexed by fault group id */
 	struct xarray faults;
 };
@@ -459,6 +460,12 @@ iommufd_get_fault(struct iommufd_ucmd *ucmd, u32 id)
 int iommufd_fault_alloc(struct iommufd_ucmd *ucmd);
 void iommufd_fault_destroy(struct iommufd_object *obj);
 int iommufd_fault_iopf_handler(struct iopf_group *group);
+int iommufd_fault_domain_attach_dev(struct iommufd_hw_pagetable *hwpt,
+				    struct iommufd_device *idev);
+void iommufd_fault_domain_detach_dev(struct iommufd_hw_pagetable *hwpt,
+				     struct iommufd_device *idev);
+int iommufd_fault_domain_replace_dev(struct iommufd_hw_pagetable *hwpt,
+				     struct iommufd_device *idev);
 
 #ifdef CONFIG_IOMMUFD_TEST
 int iommufd_test(struct iommufd_ucmd *ucmd);
diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index d70913ee8fdf..c4737e876ebc 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -377,7 +377,10 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 	 * attachment.
 	 */
 	if (list_empty(&idev->igroup->device_list)) {
-		rc = iommu_attach_group(hwpt->domain, idev->igroup->group);
+		if (hwpt->fault_capable)
+			rc = iommufd_fault_domain_attach_dev(hwpt, idev);
+		else
+			rc = iommu_attach_group(hwpt->domain, idev->igroup->group);
 		if (rc)
 			goto err_unresv;
 		idev->igroup->hwpt = hwpt;
@@ -403,7 +406,10 @@ iommufd_hw_pagetable_detach(struct iommufd_device *idev)
 	mutex_lock(&idev->igroup->lock);
 	list_del(&idev->group_item);
 	if (list_empty(&idev->igroup->device_list)) {
-		iommu_detach_group(hwpt->domain, idev->igroup->group);
+		if (hwpt->fault_capable)
+			iommufd_fault_domain_detach_dev(hwpt, idev);
+		else
+			iommu_detach_group(hwpt->domain, idev->igroup->group);
 		idev->igroup->hwpt = NULL;
 	}
 	if (hwpt_is_paging(hwpt))
@@ -498,7 +504,10 @@ iommufd_device_do_replace(struct iommufd_device *idev,
 			goto err_unlock;
 	}
 
-	rc = iommu_group_replace_domain(igroup->group, hwpt->domain);
+	if (old_hwpt->fault_capable || hwpt->fault_capable)
+		rc = iommufd_fault_domain_replace_dev(hwpt, idev);
+	else
+		rc = iommu_group_replace_domain(igroup->group, hwpt->domain);
 	if (rc)
 		goto err_unresv;
 
diff --git a/drivers/iommu/iommufd/fault.c b/drivers/iommu/iommufd/fault.c
index e752d1c49dde..a4a49f3cd4c2 100644
--- a/drivers/iommu/iommufd/fault.c
+++ b/drivers/iommu/iommufd/fault.c
@@ -267,3 +267,125 @@ int iommufd_fault_iopf_handler(struct iopf_group *group)
 
 	return 0;
 }
+
+static void release_attach_cookie(struct iopf_attach_cookie *cookie)
+{
+	struct iommufd_hw_pagetable *hwpt = cookie->domain->fault_data;
+	struct iommufd_device *idev = cookie->private;
+
+	refcount_dec(&idev->obj.users);
+	refcount_dec(&hwpt->obj.users);
+	kfree(cookie);
+}
+
+static int iommufd_fault_iopf_enable(struct iommufd_device *idev)
+{
+	int ret;
+
+	if (idev->iopf_enabled)
+		return 0;
+
+	ret = iommu_dev_enable_feature(idev->dev, IOMMU_DEV_FEAT_IOPF);
+	if (ret)
+		return ret;
+
+	idev->iopf_enabled = true;
+
+	return 0;
+}
+
+static void iommufd_fault_iopf_disable(struct iommufd_device *idev)
+{
+	if (!idev->iopf_enabled)
+		return;
+
+	iommu_dev_disable_feature(idev->dev, IOMMU_DEV_FEAT_IOPF);
+	idev->iopf_enabled = false;
+}
+
+int iommufd_fault_domain_attach_dev(struct iommufd_hw_pagetable *hwpt,
+				    struct iommufd_device *idev)
+{
+	struct iopf_attach_cookie *cookie;
+	int ret;
+
+	cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
+	if (!cookie)
+		return -ENOMEM;
+
+	refcount_inc(&hwpt->obj.users);
+	refcount_inc(&idev->obj.users);
+	cookie->release = release_attach_cookie;
+	cookie->private = idev;
+
+	if (!idev->iopf_enabled) {
+		ret = iommufd_fault_iopf_enable(idev);
+		if (ret)
+			goto out_put_cookie;
+	}
+
+	ret = iopf_domain_attach(hwpt->domain, idev->dev, IOMMU_NO_PASID, cookie);
+	if (ret)
+		goto out_disable_iopf;
+
+	return 0;
+out_disable_iopf:
+	iommufd_fault_iopf_disable(idev);
+out_put_cookie:
+	release_attach_cookie(cookie);
+
+	return ret;
+}
+
+void iommufd_fault_domain_detach_dev(struct iommufd_hw_pagetable *hwpt,
+				     struct iommufd_device *idev)
+{
+	iopf_domain_detach(hwpt->domain, idev->dev, IOMMU_NO_PASID);
+	iommufd_fault_iopf_disable(idev);
+}
+
+int iommufd_fault_domain_replace_dev(struct iommufd_hw_pagetable *hwpt,
+				     struct iommufd_device *idev)
+{
+	bool iopf_enabled_originally = idev->iopf_enabled;
+	struct iopf_attach_cookie *cookie = NULL;
+	int ret;
+
+	if (hwpt->fault_capable) {
+		cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
+		if (!cookie)
+			return -ENOMEM;
+
+		refcount_inc(&hwpt->obj.users);
+		refcount_inc(&idev->obj.users);
+		cookie->release = release_attach_cookie;
+		cookie->private = idev;
+
+		if (!idev->iopf_enabled) {
+			ret = iommufd_fault_iopf_enable(idev);
+			if (ret) {
+				release_attach_cookie(cookie);
+				return ret;
+			}
+		}
+	}
+
+	ret = iopf_domain_replace(hwpt->domain, idev->dev, IOMMU_NO_PASID, cookie);
+	if (ret) {
+		goto out_put_cookie;
+	}
+
+	if (iopf_enabled_originally && !hwpt->fault_capable)
+		iommufd_fault_iopf_disable(idev);
+
+	return 0;
+out_put_cookie:
+	if (hwpt->fault_capable)
+		release_attach_cookie(cookie);
+	if (iopf_enabled_originally && !idev->iopf_enabled)
+		iommufd_fault_iopf_enable(idev);
+	else if (!iopf_enabled_originally && idev->iopf_enabled)
+		iommufd_fault_iopf_disable(idev);
+
+	return ret;
+}
-- 
2.34.1