[PATCH 12/14] iommufd: Add APIs to preserve/unpreserve a vfio cdev

Samiullah Khawaja
2026-02-03T22:10:10Z

Add APIs that can be used to preserve and unpreserve a vfio cdev. Use
the APIs exported by the IOMMU core to preserve/unpreserve device. Pass
the LUO preservation token of the attached iommufd into IOMMU preserve
device API. This establishes the ownership of the device with the
preserved iommufd.

Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
---
drivers/iommu/iommufd/device.c | 69 ++++++++++++++++++++++++++++++++++
include/linux/iommufd.h | 23 ++++++++++++
2 files changed, 92 insertions(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 4c842368289f..30cb5218093b 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -2,6 +2,7 @@
/* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
*/
#include <linux/iommu.h>
+#include <linux/iommu-lu.h>
#include <linux/iommufd.h>
#include <linux/pci-ats.h>
#include <linux/slab.h>
@@ -1661,3 +1662,71 @@ int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
iommufd_put_object(ucmd->ictx, &idev->obj);
return rc;
}
+
+#ifdef CONFIG_IOMMU_LIVEUPDATE
+int iommufd_device_preserve(struct liveupdate_session *s,
+ struct iommufd_device *idev,
+ u64 *tokenp)
+{
+ struct iommufd_group *igroup = idev->igroup;
+ struct iommufd_hwpt_paging *hwpt_paging;
+ struct iommufd_hw_pagetable *hwpt;
+ struct iommufd_attach *attach;
+ int ret;
+
+ mutex_lock(&igroup->lock);
+ attach = xa_load(&igroup->pasid_attach, IOMMU_NO_PASID);
+ if (!attach) {
+ ret = -ENOENT;
+ goto out;
+ }
+
+ hwpt = attach->hwpt;
+ hwpt_paging = find_hwpt_paging(hwpt);
+ if (!hwpt_paging || !hwpt_paging->lu_preserve) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = liveupdate_get_token_outgoing(s, idev->ictx->file, tokenp);
+ if (ret)
+ goto out;
+
+ ret = iommu_preserve_device(hwpt_paging->common.domain,
+ idev->dev,
+ *tokenp);
+out:
+ mutex_unlock(&igroup->lock);
+ return ret;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_preserve, "IOMMUFD");
+
+void iommufd_device_unpreserve(struct liveupdate_session *s,
+ struct iommufd_device *idev,
+ u64 token)
+{
+ struct iommufd_group *igroup = idev->igroup;
+ struct iommufd_hwpt_paging *hwpt_paging;
+ struct iommufd_hw_pagetable *hwpt;
+ struct iommufd_attach *attach;
+
+ mutex_lock(&igroup->lock);
+ attach = xa_load(&igroup->pasid_attach, IOMMU_NO_PASID);
+ if (!attach) {
+ WARN_ON(-ENOENT);
+ goto out;
+ }
+
+ hwpt = attach->hwpt;
+ hwpt_paging = find_hwpt_paging(hwpt);
+ if (!hwpt_paging || !hwpt_paging->lu_preserve) {
+ WARN_ON(-EINVAL);
+ goto out;
+ }
+
+ iommu_unpreserve_device(hwpt_paging->common.domain, idev->dev);
+out:
+ mutex_unlock(&igroup->lock);
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_unpreserve, "IOMMUFD");
+#endif
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 6e7efe83bc5d..c4b3ed5b518c 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -9,6 +9,7 @@
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/iommu.h>
+#include <linux/liveupdate.h>
#include <linux/refcount.h>
#include <linux/types.h>
#include <linux/xarray.h>
@@ -71,6 +72,28 @@ void iommufd_device_detach(struct iommufd_device *idev, ioasid_t pasid);
struct iommufd_ctx *iommufd_device_to_ictx(struct iommufd_device *idev);
u32 iommufd_device_to_id(struct iommufd_device *idev);

+#ifdef CONFIG_IOMMU_LIVEUPDATE
+int iommufd_device_preserve(struct liveupdate_session *s,
+ struct iommufd_device *idev,
+ u64 *tokenp);
+void iommufd_device_unpreserve(struct liveupdate_session *s,
+ struct iommufd_device *idev,
+ u64 token);
+#else
+static inline int iommufd_device_preserve(struct liveupdate_session *s,
+ struct iommufd_device *idev,
+ u64 *tokenp)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline void iommufd_device_unpreserve(struct liveupdate_session *s,
+ struct iommufd_device *idev,
+ u64 token)
+{
+}
+#endif
+
struct iommufd_access_ops {
u8 needs_pin_pages : 1;
void (*unmap)(void *data, unsigned long iova, unsigned long length);
--
2.53.0.rc2.204.g2597b5adb4-goog