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Message-ID: <20251202230303.1017519-5-skhawaja@google.com>
Date: Tue, 2 Dec 2025 23:02:34 +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: YiFei Zhu <zhuyifei@...gle.com>, 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, Chris Li <chrisl@...nel.org>,
praan@...gle.com
Subject: [RFC PATCH v2 04/32] iommufd-lu: Implement basic prepare/cancel/finish/retrieve
using folios
From: YiFei Zhu <zhuyifei@...gle.com>
The actual serialization and de-serialization is implemented in
follow up commits.
- On prepare, a single folio is created and preserved to store
all the structs.
- On cancel, the folio is unpreserved and freed.
- On retrieve, the folio is restored, then an fd with anon_inode
is created, with data pointing to the folio.
- On finish, the folio is freed.
Signed-off-by: YiFei Zhu <zhuyifei@...gle.com>
Signed-off-by: Samiullah Khawaja <skhawaja@...gle.com>
---
MAINTAINERS | 1 +
drivers/iommu/iommufd/iommufd_private.h | 7 ++
drivers/iommu/iommufd/liveupdate.c | 113 ++++++++++++++++++++++--
drivers/iommu/iommufd/main.c | 2 +-
include/linux/kho/abi/iommufd.h | 31 +++++++
5 files changed, 148 insertions(+), 6 deletions(-)
create mode 100644 include/linux/kho/abi/iommufd.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 3bb9edf09f0e..bfe646d1c74f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13243,6 +13243,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd.git
F: Documentation/userspace-api/iommufd.rst
F: drivers/iommu/iommufd/
F: include/linux/iommufd.h
+F: include/linux/kho/abi/iommufd.h
F: include/uapi/linux/iommufd.h
F: tools/testing/selftests/iommu/
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index b6959ad55ad4..dfe9120aced0 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -21,6 +21,9 @@ struct iommu_option;
struct iommufd_device;
struct dma_buf_attachment;
struct dma_buf_phys_vec;
+struct iommufd_lu;
+
+extern const struct file_operations iommufd_fops;
struct iommufd_sw_msi_map {
struct list_head sw_msi_item;
@@ -57,6 +60,10 @@ struct iommufd_ctx {
/* Compatibility with VFIO no iommu */
u8 no_iommu_mode;
struct iommufd_ioas *vfio_ioas;
+
+#ifdef CONFIG_LIVEUPDATE
+ struct iommufd_lu *lu;
+#endif
};
/* Entry for iommufd_ctx::mt_mmap */
diff --git a/drivers/iommu/iommufd/liveupdate.c b/drivers/iommu/iommufd/liveupdate.c
index d228157b6fed..a9b5956c0dee 100644
--- a/drivers/iommu/iommufd/liveupdate.c
+++ b/drivers/iommu/iommufd/liveupdate.c
@@ -2,15 +2,44 @@
#define pr_fmt(fmt) "iommufd: " fmt
+#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/iommufd.h>
+#include <linux/kexec_handover.h>
+#include <linux/kho/abi/iommufd.h>
#include <linux/liveupdate.h>
+#include <linux/mm.h>
#include "iommufd_private.h"
static int iommufd_liveupdate_preserve(struct liveupdate_file_op_args *args)
{
- return -EOPNOTSUPP;
+ struct iommufd_ctx *ictx = iommufd_ctx_from_file(args->file);
+ struct iommufd_lu *iommufd_lu;
+ size_t serial_size;
+ void *mem;
+ int rc;
+
+ if (IS_ERR(ictx))
+ return PTR_ERR(ictx);
+
+ serial_size = sizeof(*iommufd_lu);
+
+ mem = kho_alloc_preserve(serial_size);
+ if (!mem) {
+ rc = -ENOMEM;
+ goto err_ctx_put;
+ }
+
+ iommufd_lu = mem;
+
+ args->serialized_data = virt_to_phys(iommufd_lu);
+ iommufd_ctx_put(ictx);
+ return 0;
+
+err_ctx_put:
+ iommufd_ctx_put(ictx);
+ return rc;
}
static int iommufd_liveupdate_freeze(struct liveupdate_file_op_args *args)
@@ -21,26 +50,100 @@ static int iommufd_liveupdate_freeze(struct liveupdate_file_op_args *args)
static void iommufd_liveupdate_unpreserve(struct liveupdate_file_op_args *args)
{
+ struct iommufd_ctx *ictx = iommufd_ctx_from_file(args->file);
+
+ if (WARN_ON(IS_ERR(ictx)))
+ return;
+
+ kho_unpreserve_free(phys_to_virt(args->serialized_data));
+ iommufd_ctx_put(ictx);
}
static int iommufd_liveupdate_retrieve(struct liveupdate_file_op_args *args)
{
- return -EOPNOTSUPP;
+ struct iommufd_lu *iommufd_lu;
+ struct iommufd_ctx *ictx;
+ struct folio *folio_lu;
+ struct file *file;
+ int rc;
+
+ folio_lu = kho_restore_folio(args->serialized_data);
+ if (IS_ERR_OR_NULL(folio_lu))
+ return -EFAULT;
+
+ iommufd_lu = folio_address(folio_lu);
+
+ file = anon_inode_create_getfile("iommufd", &iommufd_fops,
+ NULL, O_RDWR, NULL);
+ if (IS_ERR(file)) {
+ rc = PTR_ERR(file);
+ goto err_folio_put;
+ }
+
+ rc = iommufd_fops.open(file->f_inode, file);
+ if (rc)
+ goto err_fput;
+
+ ictx = iommufd_ctx_from_file(file);
+ if (WARN_ON(IS_ERR(ictx))) {
+ rc = PTR_ERR(ictx);
+ goto err_fput;
+ }
+
+ if (WARN_ON(ictx->lu)) {
+ rc = -EEXIST;
+ goto err_ctx_put;
+ }
+ ictx->lu = iommufd_lu;
+
+ iommufd_ctx_put(ictx);
+
+ args->file = file;
+
+ return 0;
+
+err_ctx_put:
+ iommufd_ctx_put(ictx);
+err_fput:
+ fput(file);
+err_folio_put:
+ folio_put(folio_lu);
+ return rc;
}
static bool iommufd_liveupdate_can_finish(struct liveupdate_file_op_args *args)
{
- return false;
+ if (!args->retrieved || !args->file) {
+ pr_warn("%s: fd not reclaimed\n", __func__);
+ return false;
+ }
+
+ return true;
}
static void iommufd_liveupdate_finish(struct liveupdate_file_op_args *args)
{
+ struct iommufd_lu *iommufd_lu;
+ struct iommufd_ctx *ictx;
+
+ ictx = iommufd_ctx_from_file(args->file);
+ iommufd_lu = ictx->lu;
+ ictx->lu = NULL;
+ iommufd_ctx_put(ictx);
+
+ folio_put(virt_to_folio(iommufd_lu));
}
static bool iommufd_liveupdate_can_preserve(struct liveupdate_file_handler *handler,
struct file *file)
{
- return false;
+ struct iommufd_ctx *ictx = iommufd_ctx_from_file(file);
+
+ if (IS_ERR(ictx))
+ return false;
+
+ iommufd_ctx_put(ictx);
+ return true;
}
static struct liveupdate_file_ops iommufd_lu_file_ops = {
@@ -54,7 +157,7 @@ static struct liveupdate_file_ops iommufd_lu_file_ops = {
};
static struct liveupdate_file_handler iommufd_lu_handler = {
- .compatible = "iommufd-v1",
+ .compatible = IOMMUFD_LUO_COMPATIBLE,
.ops = &iommufd_lu_file_ops,
};
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 18cc4af0a5c4..12601f9ad217 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -610,7 +610,7 @@ static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma)
return rc;
}
-static const struct file_operations iommufd_fops = {
+const struct file_operations iommufd_fops = {
.owner = THIS_MODULE,
.open = iommufd_fops_open,
.release = iommufd_fops_release,
diff --git a/include/linux/kho/abi/iommufd.h b/include/linux/kho/abi/iommufd.h
new file mode 100644
index 000000000000..19d6b61ec3c3
--- /dev/null
+++ b/include/linux/kho/abi/iommufd.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (C) 2025, Google LLC
+ * Author: Samiullah Khawaja <skhawaja@...gle.com>
+ */
+
+#ifndef _LINUX_KHO_ABI_IOMMUFD_H
+#define _LINUX_KHO_ABI_IOMMUFD_H
+
+#include <linux/mutex_types.h>
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+/**
+ * DOC: IOMMUFD Live Update ABI
+ *
+ * This header defines the ABI for preserving the state of an IOMMUFD file
+ * across a kexec reboot using LUO.
+ *
+ * This interface is a contract. Any modification to any of the serialization
+ * structs defined here constitutes a breaking change. Such changes require
+ * incrementing the version number in the IOMMUFD_LUO_COMPATIBLE string.
+ */
+
+#define IOMMUFD_LUO_COMPATIBLE "iommufd-v1"
+
+struct iommufd_lu {
+};
+
+#endif /* _LINUX_KHO_ABI_IOMMUFD_H */
--
2.52.0.158.g65b55ccf14-goog
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