linux-kernel - [RFC PATCH v2 18/32] iommufd: Add APIs to preserve/unpreserve a vfio cdev

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Message-ID: <20251202230303.1017519-19-skhawaja@google.com>
Date: Tue,  2 Dec 2025 23:02:48 +0000
From: Samiullah Khawaja <skhawaja@...gle.com>
To: David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>, 
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, Jason Gunthorpe <jgg@...pe.ca>, iommu@...ts.linux.dev
Cc: Samiullah Khawaja <skhawaja@...gle.com>, Robin Murphy <robin.murphy@....com>, 
	Pratyush Yadav <pratyush@...nel.org>, Kevin Tian <kevin.tian@...el.com>, 
	Alex Williamson <alex@...zbot.org>, linux-kernel@...r.kernel.org, 
	Saeed Mahameed <saeedm@...dia.com>, Adithya Jayachandran <ajayachandra@...dia.com>, 
	Parav Pandit <parav@...dia.com>, Leon Romanovsky <leonro@...dia.com>, William Tu <witu@...dia.com>, 
	Vipin Sharma <vipinsh@...gle.com>, dmatlack@...gle.com, YiFei Zhu <zhuyifei@...gle.com>, 
	Chris Li <chrisl@...nel.org>, praan@...gle.com
Subject: [RFC PATCH v2 18/32] iommufd: Add APIs to preserve/unpreserve a vfio cdev

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. Once
preserved, the token is returned to the caller so it can be used to
restore/rebind to the device after liveupdate.

Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
 drivers/iommu/iommufd/device.c | 39 ++++++++++++++++++++++++++++++++++
 include/linux/iommufd.h        |  6 ++++++
 2 files changed, 45 insertions(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index ba4d9c3cfa8b..2c81bfa7dedd 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>
@@ -1666,3 +1667,41 @@ int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
 	iommufd_put_object(ucmd->ictx, &idev->obj);
 	return rc;
 }
+
+#ifdef CONFIG_LIVEUPDATE
+int iommufd_device_preserve(struct iommufd_device *idev, ioasid_t pasid)
+{
+	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, pasid);
+	if (!attach) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	hwpt = attach->hwpt;
+	hwpt_paging = find_hwpt_paging(hwpt);
+	if (!hwpt_paging || !hwpt_paging->lu_preserved) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* TODO: Add support PASIDs */
+	ret = iommu_preserve_device(hwpt_paging->common.domain, idev->dev);
+
+out:
+	mutex_unlock(&igroup->lock);
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_preserve, "IOMMUFD");
+
+void iommufd_device_unpreserve(struct iommufd_device *idev)
+{
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_unpreserve, "IOMMUFD");
+#endif
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 6e7efe83bc5d..ba433fb1a481 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 +72,11 @@ 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_LIVEUPDATE
+int iommufd_device_preserve(struct iommufd_device *idev, ioasid_t pasid);
+void iommufd_device_unpreserve(struct iommufd_device *idev);
+#endif
+
 struct iommufd_access_ops {
 	u8 needs_pin_pages : 1;
 	void (*unmap)(void *data, unsigned long iova, unsigned long length);
-- 
2.52.0.158.g65b55ccf14-goog