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Message-ID: <20251126193608.2678510-5-dmatlack@google.com>
Date: Wed, 26 Nov 2025 19:35:51 +0000
From: David Matlack <dmatlack@...gle.com>
To: Alex Williamson <alex@...zbot.org>
Cc: Adithya Jayachandran <ajayachandra@...dia.com>, Alex Mastro <amastro@...com>,
Alistair Popple <apopple@...dia.com>, Andrew Morton <akpm@...ux-foundation.org>,
Bjorn Helgaas <bhelgaas@...gle.com>, Chris Li <chrisl@...nel.org>,
David Matlack <dmatlack@...gle.com>, David Rientjes <rientjes@...gle.com>,
Jacob Pan <jacob.pan@...ux.microsoft.com>, Jason Gunthorpe <jgg@...dia.com>,
Jason Gunthorpe <jgg@...pe.ca>, Josh Hilke <jrhilke@...gle.com>, Kevin Tian <kevin.tian@...el.com>,
kvm@...r.kernel.org, Leon Romanovsky <leonro@...dia.com>, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-pci@...r.kernel.org,
Lukas Wunner <lukas@...ner.de>, Mike Rapoport <rppt@...nel.org>, Parav Pandit <parav@...dia.com>,
Pasha Tatashin <pasha.tatashin@...een.com>, Philipp Stanner <pstanner@...hat.com>,
Pratyush Yadav <pratyush@...nel.org>, Saeed Mahameed <saeedm@...dia.com>,
Samiullah Khawaja <skhawaja@...gle.com>, Shuah Khan <shuah@...nel.org>,
Tomita Moeko <tomitamoeko@...il.com>, Vipin Sharma <vipinsh@...gle.com>, William Tu <witu@...dia.com>,
Yi Liu <yi.l.liu@...el.com>, Yunxiang Li <Yunxiang.Li@....com>,
Zhu Yanjun <yanjun.zhu@...ux.dev>
Subject: [PATCH 04/21] vfio/pci: Register a file handler with Live Update Orchestrator
From: Vipin Sharma <vipinsh@...gle.com>
Register a live update file handler for vfio-pci device files. Add stub
implementations of all required callbacks so that registration does not
fail (i.e. to avoid breaking git-bisect).
This file handler will be extended in subsequent commits to enable a
device bound to vfio-pci to run without interruption while the host is
going through a kexec Live Update.
Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
Co-Developed-by: David Matlack <dmatlack@...gle.com>
Signed-off-by: David Matlack <dmatlack@...gle.com>
---
MAINTAINERS | 1 +
drivers/vfio/pci/Makefile | 1 +
drivers/vfio/pci/vfio_pci.c | 9 +++-
drivers/vfio/pci/vfio_pci_liveupdate.c | 69 ++++++++++++++++++++++++++
drivers/vfio/pci/vfio_pci_priv.h | 14 ++++++
include/linux/kho/abi/vfio_pci.h | 28 +++++++++++
6 files changed, 121 insertions(+), 1 deletion(-)
create mode 100644 drivers/vfio/pci/vfio_pci_liveupdate.c
create mode 100644 include/linux/kho/abi/vfio_pci.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 2722f98d0ed7..ff50977277c4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26933,6 +26933,7 @@ F: Documentation/ABI/testing/debugfs-vfio
F: Documentation/ABI/testing/sysfs-devices-vfio-dev
F: Documentation/driver-api/vfio.rst
F: drivers/vfio/
+F: include/linux/kho/abi/vfio_pci.h
F: include/linux/vfio.h
F: include/linux/vfio_pci_core.h
F: include/uapi/linux/vfio.h
diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
index cf00c0a7e55c..929df22c079b 100644
--- a/drivers/vfio/pci/Makefile
+++ b/drivers/vfio/pci/Makefile
@@ -2,6 +2,7 @@
vfio-pci-core-y := vfio_pci_core.o vfio_pci_intrs.o vfio_pci_rdwr.o vfio_pci_config.o
vfio-pci-core-$(CONFIG_VFIO_PCI_ZDEV_KVM) += vfio_pci_zdev.o
+vfio-pci-core-$(CONFIG_LIVEUPDATE) += vfio_pci_liveupdate.o
obj-$(CONFIG_VFIO_PCI_CORE) += vfio-pci-core.o
vfio-pci-y := vfio_pci.o
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index ac10f14417f2..c2fe34a830d8 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -252,6 +252,10 @@ static int __init vfio_pci_init(void)
int ret;
bool is_disable_vga = true;
+ ret = vfio_pci_liveupdate_init();
+ if (ret)
+ return ret;
+
#ifdef CONFIG_VFIO_PCI_VGA
is_disable_vga = disable_vga;
#endif
@@ -260,8 +264,10 @@ static int __init vfio_pci_init(void)
/* Register and scan for devices */
ret = pci_register_driver(&vfio_pci_driver);
- if (ret)
+ if (ret) {
+ vfio_pci_liveupdate_cleanup();
return ret;
+ }
vfio_pci_fill_ids();
@@ -275,6 +281,7 @@ module_init(vfio_pci_init);
static void __exit vfio_pci_cleanup(void)
{
pci_unregister_driver(&vfio_pci_driver);
+ vfio_pci_liveupdate_cleanup();
}
module_exit(vfio_pci_cleanup);
diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
new file mode 100644
index 000000000000..b84e63c0357b
--- /dev/null
+++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Vipin Sharma <vipinsh@...gle.com>
+ * David Matlack <dmatlack@...gle.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kho/abi/vfio_pci.h>
+#include <linux/liveupdate.h>
+#include <linux/errno.h>
+
+#include "vfio_pci_priv.h"
+
+static bool vfio_pci_liveupdate_can_preserve(struct liveupdate_file_handler *handler,
+ struct file *file)
+{
+ return false;
+}
+
+static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
+{
+ return -EOPNOTSUPP;
+}
+
+static void vfio_pci_liveupdate_unpreserve(struct liveupdate_file_op_args *args)
+{
+}
+
+static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_op_args *args)
+{
+ return -EOPNOTSUPP;
+}
+
+static void vfio_pci_liveupdate_finish(struct liveupdate_file_op_args *args)
+{
+}
+
+static const struct liveupdate_file_ops vfio_pci_liveupdate_file_ops = {
+ .can_preserve = vfio_pci_liveupdate_can_preserve,
+ .preserve = vfio_pci_liveupdate_preserve,
+ .unpreserve = vfio_pci_liveupdate_unpreserve,
+ .retrieve = vfio_pci_liveupdate_retrieve,
+ .finish = vfio_pci_liveupdate_finish,
+ .owner = THIS_MODULE,
+};
+
+static struct liveupdate_file_handler vfio_pci_liveupdate_fh = {
+ .ops = &vfio_pci_liveupdate_file_ops,
+ .compatible = VFIO_PCI_LUO_FH_COMPATIBLE,
+};
+
+int __init vfio_pci_liveupdate_init(void)
+{
+ if (!liveupdate_enabled())
+ return 0;
+
+ return liveupdate_register_file_handler(&vfio_pci_liveupdate_fh);
+}
+
+void vfio_pci_liveupdate_cleanup(void)
+{
+ if (!liveupdate_enabled())
+ return;
+
+ liveupdate_unregister_file_handler(&vfio_pci_liveupdate_fh);
+}
diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
index a9972eacb293..b9f7c4e2b4df 100644
--- a/drivers/vfio/pci/vfio_pci_priv.h
+++ b/drivers/vfio/pci/vfio_pci_priv.h
@@ -107,4 +107,18 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
return (pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA;
}
+#ifdef CONFIG_LIVEUPDATE
+int __init vfio_pci_liveupdate_init(void);
+void vfio_pci_liveupdate_cleanup(void);
+#else
+static inline int vfio_pci_liveupdate_init(void)
+{
+ return 0;
+}
+
+static inline void vfio_pci_liveupdate_cleanup(void)
+{
+}
+#endif /* CONFIG_LIVEUPDATE */
+
#endif
diff --git a/include/linux/kho/abi/vfio_pci.h b/include/linux/kho/abi/vfio_pci.h
new file mode 100644
index 000000000000..37a845eed972
--- /dev/null
+++ b/include/linux/kho/abi/vfio_pci.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Vipin Sharma <vipinsh@...gle.com>
+ * David Matlack <dmatlack@...gle.com>
+ */
+
+#ifndef _LINUX_LIVEUPDATE_ABI_VFIO_PCI_H
+#define _LINUX_LIVEUPDATE_ABI_VFIO_PCI_H
+
+/**
+ * DOC: VFIO PCI Live Update ABI
+ *
+ * This header defines the ABI for preserving the state of a VFIO PCI device
+ * files across a kexec reboot using LUO.
+ *
+ * Device metadata is serialized into memory which is then handed to the next
+ * kernel via KHO.
+ *
+ * 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 VFIO_PCI_LUO_FH_COMPATIBLE string.
+ */
+
+#define VFIO_PCI_LUO_FH_COMPATIBLE "vfio-pci-v1"
+
+#endif /* _LINUX_LIVEUPDATE_ABI_VFIO_PCI_H */
--
2.52.0.487.g5c8c507ade-goog
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